Extending the ionic conductivity is the pre-requisite of electrolytes in fuel cell technology for high-electrochemical performance.In this regard,the introduction of semiconductor-oxide materials and the approach of h...Extending the ionic conductivity is the pre-requisite of electrolytes in fuel cell technology for high-electrochemical performance.In this regard,the introduction of semiconductor-oxide materials and the approach of heterostructure formation by modulating energy bands to enhance ionic conduction acting as an electrolyte in fuel cell-device.Semiconductor(n-type;SnO_(2))plays a key role by introducing into p-type SrFe_(0.2)Ti_(0.8)O_(3-δ)(SFT)semiconductor perovskite materials to construct p-n heterojunction for high ionic conductivity.Therefore,two different composites of SFT and SnO_(2)are constructed by gluing p-and n-type SFT-SnO_(2),where the optimal composition of SFT-SnO_(2)(6∶4)heterostructure electrolyte-based fuel cell achieved excellent ionic conductivity 0.24 S cm^(-1)with power-output of 1004 mW cm^(-2)and high OCV 1.12 V at a low operational temperature of 500℃.The high power-output and significant ionic conductivity with durable operation of 54 h are accredited to SFT-SnO_(2)heterojunction formation including interfacial conduction assisted by a built-in electric field in fuel cell device.Moreover,the fuel conversion efficiency and considerable Faradaic efficiency reveal the compatibility of SFT-SnO_(2)heterostructure electrolyte and ruled-out short-circuiting issue.Further,the first principle calculation provides sufficient information on structure optimization and energy-band structure modulation of SFT-SnO_(2).This strategy will provide new insight into semiconductor-based fuel cell technology to design novel electrolytes.展开更多
The energy band properties, density of states, and band alignment of the BexZn1-xO1-ySy alloy （Be- and S-doped wurtzite ZnO） are investigated by the first-principles method. BexZn1-xO1-ySy alloy is a direct band gap...The energy band properties, density of states, and band alignment of the BexZn1-xO1-ySy alloy （Be- and S-doped wurtzite ZnO） are investigated by the first-principles method. BexZn1-xO1-ySy alloy is a direct band gap semiconductor, the valence band maximum （VBM） and the conduction band minimum （CBM） of BexZn1-xO1-ySy are dominated by S 3p and Zn 4s states, respectively. The band gap and lattice constant of BexZn1-xO1-ySy alloy can be modulated by changing the doped content values x and y. With the increase in Be content value x in the BexZnl-xOl-ySy alloy, the band gap increases and the lattice constant reduces, but the situation is just the opposite when increasing the S content value y in the BexZn1-xO1-ySy alloy. Because the lattice constant of Be0.375Zn0.625O0.75S0.25 alloy is well matched with that of ZnO and its energy gap is large compared with that of ZnO, so the Be0.375Zn0.625O0.75S0.25 alloy is suitable for serving as the blocking material for a high-quality ZnO-based device.展开更多
Modulating the electronic structure of a photocatalyst and constructing spatially separated redox sites are key strategies for achieving the photocatalytic dual-channel generation of H_(2)O_(2).In this study,a graphen...Modulating the electronic structure of a photocatalyst and constructing spatially separated redox sites are key strategies for achieving the photocatalytic dual-channel generation of H_(2)O_(2).In this study,a graphene-modified non-compensated Cu/N-co-doped titanium dioxide(Cu-N-TiO_(2)/rGO)photocatalyst was designed for the efficient synthesis of H_(2)O_(2) via a dual-channel pathway.Precise modulation of the TiO_(2) conduction band position was achieved through the synergistic coupling of Cu 3d orbitals hybridized with Ti 3d orbitals and hybridization of N 2p orbitals with O 2p orbitals.This approach significantly improved the utilization of sunlight while satisfying the redox potential requirements.Cu doping not only promoted the formation of oxygen vacancies but also reduced the formation of Ti^(3+)ions,the photogenerated charge recombination centers.The non-compensated doping of N effectively increased the solubility of Cu^(2+)ions in the titanium dioxide lattice,enhanced the adsorption of hydroxyl radical intermediates,and created conditions for the subsequent hydroxyl radical combinations promoting the generation of H_(2)O_(2).In addition,the introduction of highly conductive graphene improved the interfacial carrier separation efficiency while realizing the spatial separation of redox sites,creating conditions for dual-channel reactions.The experimental results showed that the H_(2)O_(2) yield of Cu-N-TiO_(2)/rGO under simulated sunlight reached 1266.7μmol/L,which was 25.2 times higher than that of pristine TiO_(2).This study elucidated the synergistic mechanism of the energy band structure modulation and interfacial optimization,which provided a new idea for the design of dual-channel H_(2)O_(2) production photocatalysts.展开更多
The molybdenum carbide(Mo_(2)C)has been regarded as one of the most cost-efficient and stable electrocatalyst for the hydrogen evolution reaction(HER)by the virtue of its Pt-like electronic structures.However,the inhe...The molybdenum carbide(Mo_(2)C)has been regarded as one of the most cost-efficient and stable electrocatalyst for the hydrogen evolution reaction(HER)by the virtue of its Pt-like electronic structures.However,the inherent limitation of high density of empty valence band significantly reduces its catalytic reactivity by reason of strong hydrogen desorption resistance.Herein,we propose a multiscale confinement synthesis method to design the nitrogen-rich Mo_(2)C for modulating the band structure via decomposing the pre-coordination bonded polymer in a pressure-tight tube sealing system.Pre-bonded c/N-Mo in the coordination precursor constructs a micro-confinement space,enabling the homogeneous nitrogenization in-situ happened during the formation of Mo_(2)C.Simultaneously,the evolved gases from the precursor decomposition in tube sealing system establish a macro-confinement environment,preventing the lattice N escape and further endowing a continuous nitridation.Combining the multiscale confinement effects,the nitrogen-rich Mo2C displays as high as 25%N-Mo concentration in carbide lattice,leading to a satisfactory band structure.Accordingly,the constructed nitrogen-rich Mo_(2)C reveals an adorable catalytic activity for HER in both alkaline and acid solution.It is anticipated that the multiscale confinement synthesis strategy presents guideline for the rational design of electrocatalysts and beyond.展开更多
Lead(Pb)-free halide perovskites have recently attracted increasing attention as potential catalysts for CO_(2) photoreduction to CO due to their potential to capture solar energy and drive catalytic reaction.However,...Lead(Pb)-free halide perovskites have recently attracted increasing attention as potential catalysts for CO_(2) photoreduction to CO due to their potential to capture solar energy and drive catalytic reaction.However,issues of the poor charge transfer still remain one of the main obstacles limiting their performance due to the overwhelming radiative and nonradiative charge-carrier recombination losses.Herein,Pb-free Sb-alloyed all-inorganic quadruple perovskite Cs_(4)Mn(Bi_(1-x)Sb_(x))_(2)Cl_(12)(0≤x≤1)is synthesized as efficient photocatalyst.By Sb alloying,the undesired relaxation of photogenerated electrons from conduction band to emission centers of[MnCl6]^(4-)is greatly suppressed,resulting in a weakened PL emission and enhanced charge transfer for photocatalyst.The ensuing Cs_(4)Mn(Bi_(1-x)Sb_(x))_(2)Cl_(12) photocatalyst accomplishes efficient conversion of CO_(2)into CO,accompanied by a surprising production of H_(2)O_(2),a high valueadded product associated with water oxidation.By optimizing Sb^(3+) concentration,a high CO evolution rate of 35.1μmol g^(-1)h^(-1)is achieved,superior to most other Pb and Pb-free halide perovskites.Our findings provide new insights into the mixed-cation alloying strategies for improved photocatalytic performance of Pb-free perovskites and shed light on the rational design of robust band structure toward efficient energy transfer.展开更多
Organic semiconductors are inherently soft,making it possible to increase their mobilities by strains.Such a unique feature can be exploited directly in flexible electronics for improved device performance.The 2,7-dio...Organic semiconductors are inherently soft,making it possible to increase their mobilities by strains.Such a unique feature can be exploited directly in flexible electronics for improved device performance.The 2,7-dioctyl[1]benzothieno[3,2-b][1]-benzothiophene derivative,C8-BTBT is one of the best small-molecule hole transport materials.Here,we demonstrated its band structure modulation under strains by combining the non-equilibrium molecular dynamics simulations and first-principles calculations.We found that the C8-BTBT lattice undergoes a transition from monoclinic to triclinic crystal system at the temperature below 160 K.Both shear and uniaxial strains were applied to the low-temperature triclinic phase of C8-BTBT,and polymorphism was identified in the shear process.The band width enhancement is up to 8%under 2%of compressive strain along the x direction,and 14%under 4%of tensile strain along the y direction.The band structure modulation of C8-BTBT can be well related to its herringbone packing motifs,where the edge to face and edge to edge pairs constitute two-dimensional charge transport pathways and their electronic overlaps determine the band widths along the two directions respectively.These findings pave the way for utilizing strains towards improved performance of organic semiconductors on flexible substrates,for example,by bending the substrates.展开更多
We present the characteristics of a full-WDM-band photodiode module in 40 Gb/s U-band operation using a Raman amplifier. This module is suitable for wide-band transmission systems with the additional new channels in t...We present the characteristics of a full-WDM-band photodiode module in 40 Gb/s U-band operation using a Raman amplifier. This module is suitable for wide-band transmission systems with the additional new channels in the U band.展开更多
Labor-intensive,trial-and-error methods are frequently employed for modifying the perovskite surface to mitigate trap defects.There is an urgent need for rationally designed and efficient molecular passivators.To addr...Labor-intensive,trial-and-error methods are frequently employed for modifying the perovskite surface to mitigate trap defects.There is an urgent need for rationally designed and efficient molecular passivators.To address the performance and stability challenges caused by defects in polycrystalline perovskite,we have rationally designed and tailored passivation molecules,4-(trifluoromethyl)benzoic anhydride(TFBA),ethyl 4-(trifluoromethyl)benzoate(TFB),and 4-(trifluoromethyl)benzoic acid(PTF),to minimize interfacial energy loss and modulate the bandgap alignment for achieving efficient perovskite solar cells(PSCs).These molecules could target the perovskite surface defects,particularly Pb-I antisite defects,with the-COOH and trifluoromethyl functional groups at the edges.Among them,PTF exhibited superior passivation performance by coordinat-ing its carboxyl group withPb2+,effectively suppressing non-radiative recombination.Additionally,the fluorine sites in these molecules corrected lattice distortions and stabilized the perovskite structure through hydrogen bonding with MA/FA cations,reducing ion migration,and enhancing moisture resistance.As a result,PTF-modified PSCs achieved an efficiency of 25.57%and maintained over 85%of their initial efficiency after 1600 h of aging.This study provides a clear pathway for optimizing passivation strategies through rational molecular design.展开更多
In the domain of spectroscopy,miniaturization efforts often face significant challenges,particularly in achieving high spectral resolution and precise construction.Here,we introduce a computational spectrometer powere...In the domain of spectroscopy,miniaturization efforts often face significant challenges,particularly in achieving high spectral resolution and precise construction.Here,we introduce a computational spectrometer powered by a nonlinear photonic memristor with a WSe2 homojunction.This approach overcomes traditional limitations,such as constrained Fermi level tunability,persistent dark current,and limited photoresponse dimensionality through dynamic energy band modulation driven by palladium(Pd)ion migration.The critical role of Pd ion migration is thoroughly supported by first-principles calculations,numerical simulations,and experimental verification,demonstrating its effectiveness in enhancing device performance.Additionally,we integrate this dynamic modulation with a specialized nonlinear neural network tailored to address the memristor's inherent nonlinear photoresponse.This combination enables our spectrometer to achieve an exceptional peak wavelength accuracy of o.18 nm and a spectral resolution of 2 nm within the 630-640 nm range.This development marks a significant advancement in the creation of compact,high-effciency spectroscopic instruments and offers a versatile platform for applications across diverse material systems.展开更多
High-strength high-performance p-type(Bi,Sb)_(2)Te_(3)are of pivotal importance for near-room-temperature thermoelectric conversions,the reliable synthesis and fabrication has been viewed of imperative priority.It is ...High-strength high-performance p-type(Bi,Sb)_(2)Te_(3)are of pivotal importance for near-room-temperature thermoelectric conversions,the reliable synthesis and fabrication has been viewed of imperative priority.It is known that the energy-favorable formation of anti-site Sb_(Te)’and vacancy v_(Sb)'''acceptor defects from high-temperature syntheses results in additional charge carriers and scattering centers for electrical and phonon transport.However,how p-type(Bi,Sb)_(2)Te_(3)with minimal lattice defects function remains to be scrutinized.Herein,we present the synergistic enhancements of mechanical robustness and thermoelectric property in crystallographic-defect-suppressed pristine(Bi,Sb)_(2)TeBi_(2)Te_(3)through a simple mechanical alloying combined with spark-plasma-sintering(SPS)process.The Sb_(Te)’and v_(Sb)'''acceptor defects were efficiently restrained,contributing to markedly increased charge carrier mobilities.A slightly enlarged band gap of 0.24 eV underpinned enhanced thermoelectric performance for pristine Bi_(0.3)Sb_(1.7)Te_(3)over a wide temperature range,delivering high zT300 K of 1.16 and zT_(ave)of 1.21 over 300-473 K.Interestingly,the confined in-situ grain coarsening during SPS with uniform dispersive nanopores readily endowed an ultra-high compressive strength of 206 MPa,surpassing that of reported(Bi,Sb)_(2)Te_(3)so far.A 7-pair module(coupled with n-Bi_(2)Te_(3))was fabricated,demonstrating a competitiveΔT over 70 K at T_(hot)=300 K.Furthermore,a power-generation module coupled with n-Mg_(3)SbBi registered a cutting-edge thermoelectric conversion efficiency of 9.5%at a temperature gradient of 250 K.The strategy eliminates the need of complex processing nor extrinsic doping for pristine(Bi,Sb)_(2)Te_(3),demonstrating great potentials in thermoelectric power generation and cooling applications.展开更多
Element doping can break the crystal symmetry and realize the topological phase transition in quantum materials,which enables the precise modulation of energy band structure and microscopic dynamical interaction.Herei...Element doping can break the crystal symmetry and realize the topological phase transition in quantum materials,which enables the precise modulation of energy band structure and microscopic dynamical interaction.Herein,we have studied the ultrafast photocarrier dynamics in Zn-doped 3D topological Dirac semimetal Cd_(3)As_(2)utilizing time-resolved optical pump-terahertz probe spectroscopy.Comparing to the pristine Cd_(3)As_(2),we found that the relaxation time of the lightly doped alloy is slightly shorter,while that of the heavily doped alloy exhibits a significant prolongation.Pump-fluence-and temperature-dependent transient terahertz spectroscopy indicated that in pristine and lightly doped samples within nontrivial semimetal phase,the photocarrier dynamics are dominated by the cooling of Dirac fermions.In heavily doped alloy,however,the observed longer relaxation process can be attributed to interband electron-hole recombination,which is a result of doping-induced transition into a trivial semiconductor phase.Our investigation highlights that Zn-doping is an effective and flexible scheme for engineering the electronic structure and transient carrier relaxation dynamics in Cd_(3)As_(2),and offers a control knob for functional switching between diverse optoelectronic devices within the realm of practical applications.展开更多
The major impediment to the additional industrialization of water splitting is the high cost of the co-catalyst made of noble metals and the sacrificial reagent. A binary photocatalytic system, consisting of B-doped g...The major impediment to the additional industrialization of water splitting is the high cost of the co-catalyst made of noble metals and the sacrificial reagent. A binary photocatalytic system, consisting of B-doped g-C_(3)N_(4) nanosheets(Cu_(20)@BCN-X) and atomically accurate copper clusters, is designed in this study. The copper clusters serve as co-catalysts for H_(2) evolution and exhibit Pt-like activity, whereas the nanosheets serve as carriers and semiconductor components for O_(2) evolution. Such binary system, created using simple techniques, demonstrates hydrogen bonding interactions that promote synergistic effects and efficient binding and charge transfer across the interface between the two components. Band position manipulation of carbon nitride nanosheets demonstrates a Z-scheme charge transfer mechanism between the nanosheets and copper clusters. This photocatalytic system can accomplish the photocatalytic overall water splitting process(259.9 μmol g^(-1)h^(-1)of H_(2) and 129.4 μmol g^(-1)h^(-1)of O_(2)) without using sacrificial agents or noble metal co-catalysts. This work lays the foundation for the design of overall water splitting catalysts by precisely manipulating the energy levels, and it also paves the way for commercialized photocatalytic catalysts that do not require noble metals or sacrificial chemicals.展开更多
The introduction of vacancy defects in semiconductors has been proven to be a highly effective approach to improve their photocatalytic activity owing to their advantages of promoting light absorption,facilitating pho...The introduction of vacancy defects in semiconductors has been proven to be a highly effective approach to improve their photocatalytic activity owing to their advantages of promoting light absorption,facilitating photogenerated carrier separation,optimizing electronic structure,and enabling the production of reactive radicals.Herein,we outline the state-of-the-art vacancy-engineered photocatalysts in various applications and reveal how the vacancies influence photocatalytic performance.Specifically,the types of vacancy defects,the methods for tailoring vacancies,the advanced characteri-zation techniques,the categories of photocatalysts with vacancy defects,and the corresponding photocatalytic behaviors are presented.Meanwhile,the methods of vacancies creation and the related photocatalytic performance are correlated,which can be very useful to guide the readers to quickly obtain in-depth knowledge and to have a good idea about the selection of defect engineering methods.The precise characterization of vacancy defects is highly challenging.This review describes the accurate use of a series of characterization techniques with detailed comments and suggestions.This represents the uniqueness of this comprehensive review.The challenges and development prospects in engineering photocatalysts with vacancy defects for practical applications are discussed to provide a promising research direction in this field.展开更多
Facing the body＇s EEG（electroencephalograph, 0.5–100 Hz, 5–100 μV） and ECG＇s（electrocardiogram,〈 100 Hz, 0.01–5 mV） micro signal detection requirement, this paper develops a pervasive application micro sign...Facing the body＇s EEG（electroencephalograph, 0.5–100 Hz, 5–100 μV） and ECG＇s（electrocardiogram,〈 100 Hz, 0.01–5 mV） micro signal detection requirement, this paper develops a pervasive application micro signal detection ASIC chip with the chopping modulation/demodulation method. The chopper-stabilization circuit with the RRL（ripple reduction loop） circuit is to suppress the ripple voltage, which locates at the single-stage amplifier＇s outputting terminal. The single-stage chopping core＇s noise has been suppressed too, and it is beneficial for suppressing noises of post-circuit. The chopping core circuit uses the PFB（positive feedback loop） to increase the inputting resistance, and the NFB（negative feedback loop） to stabilize the 40 dB intermediate frequency gain. The cascaded switch-capacitor sample/hold circuit has been used for deleting spike noises caused by non-ideal MOS switches, and the VGA/BPF（voltage gain amplifier/band pass filter） circuit is used to tune the chopper system＇s gain/bandwidth digitally. Assisted with the designed novel dry-electrode, the real test result of the chopping amplifying circuit gives some critical parameters： 8.1 μW/channel, 0.8 μVrms（@band-widthD100 Hz）, 4216–11220 times digitally tuning gain range, etc. The data capture system uses the NI CO＇s data capturing DAQmx interface,and the captured micro EEG/ECG＇s waves are real-time displayed with the PC-Labview. The proposed chopper system is a unified EEG/ECG signal＇s detection instrument and has a critical real application value.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.32250410309 and 52105582)Natural Science Foundation of Guangdong Province(Grant No.2022A1515010894 and 2022B0303040002)+1 种基金Fundamental Research Foundation of Shenzhen(JCYJ20210324095210030 and JCYJ20220818095810023)Shenzhen-Hong Kong-Macao S&T Program(Category C:SGDX20210823103200004)
文摘Extending the ionic conductivity is the pre-requisite of electrolytes in fuel cell technology for high-electrochemical performance.In this regard,the introduction of semiconductor-oxide materials and the approach of heterostructure formation by modulating energy bands to enhance ionic conduction acting as an electrolyte in fuel cell-device.Semiconductor(n-type;SnO_(2))plays a key role by introducing into p-type SrFe_(0.2)Ti_(0.8)O_(3-δ)(SFT)semiconductor perovskite materials to construct p-n heterojunction for high ionic conductivity.Therefore,two different composites of SFT and SnO_(2)are constructed by gluing p-and n-type SFT-SnO_(2),where the optimal composition of SFT-SnO_(2)(6∶4)heterostructure electrolyte-based fuel cell achieved excellent ionic conductivity 0.24 S cm^(-1)with power-output of 1004 mW cm^(-2)and high OCV 1.12 V at a low operational temperature of 500℃.The high power-output and significant ionic conductivity with durable operation of 54 h are accredited to SFT-SnO_(2)heterojunction formation including interfacial conduction assisted by a built-in electric field in fuel cell device.Moreover,the fuel conversion efficiency and considerable Faradaic efficiency reveal the compatibility of SFT-SnO_(2)heterostructure electrolyte and ruled-out short-circuiting issue.Further,the first principle calculation provides sufficient information on structure optimization and energy-band structure modulation of SFT-SnO_(2).This strategy will provide new insight into semiconductor-based fuel cell technology to design novel electrolytes.
基金supported by the National Natural Science Foundation of China(Grant No.61078046)the Special Funds for Provincial Strategic and Emerging Industries Projects of Guangdong Province,China(Grant No.2012A080304016)the Youth Foundation of South China Normal University,China(Grant No.2012KJ018)
文摘The energy band properties, density of states, and band alignment of the BexZn1-xO1-ySy alloy （Be- and S-doped wurtzite ZnO） are investigated by the first-principles method. BexZn1-xO1-ySy alloy is a direct band gap semiconductor, the valence band maximum （VBM） and the conduction band minimum （CBM） of BexZn1-xO1-ySy are dominated by S 3p and Zn 4s states, respectively. The band gap and lattice constant of BexZn1-xO1-ySy alloy can be modulated by changing the doped content values x and y. With the increase in Be content value x in the BexZnl-xOl-ySy alloy, the band gap increases and the lattice constant reduces, but the situation is just the opposite when increasing the S content value y in the BexZn1-xO1-ySy alloy. Because the lattice constant of Be0.375Zn0.625O0.75S0.25 alloy is well matched with that of ZnO and its energy gap is large compared with that of ZnO, so the Be0.375Zn0.625O0.75S0.25 alloy is suitable for serving as the blocking material for a high-quality ZnO-based device.
文摘Modulating the electronic structure of a photocatalyst and constructing spatially separated redox sites are key strategies for achieving the photocatalytic dual-channel generation of H_(2)O_(2).In this study,a graphene-modified non-compensated Cu/N-co-doped titanium dioxide(Cu-N-TiO_(2)/rGO)photocatalyst was designed for the efficient synthesis of H_(2)O_(2) via a dual-channel pathway.Precise modulation of the TiO_(2) conduction band position was achieved through the synergistic coupling of Cu 3d orbitals hybridized with Ti 3d orbitals and hybridization of N 2p orbitals with O 2p orbitals.This approach significantly improved the utilization of sunlight while satisfying the redox potential requirements.Cu doping not only promoted the formation of oxygen vacancies but also reduced the formation of Ti^(3+)ions,the photogenerated charge recombination centers.The non-compensated doping of N effectively increased the solubility of Cu^(2+)ions in the titanium dioxide lattice,enhanced the adsorption of hydroxyl radical intermediates,and created conditions for the subsequent hydroxyl radical combinations promoting the generation of H_(2)O_(2).In addition,the introduction of highly conductive graphene improved the interfacial carrier separation efficiency while realizing the spatial separation of redox sites,creating conditions for dual-channel reactions.The experimental results showed that the H_(2)O_(2) yield of Cu-N-TiO_(2)/rGO under simulated sunlight reached 1266.7μmol/L,which was 25.2 times higher than that of pristine TiO_(2).This study elucidated the synergistic mechanism of the energy band structure modulation and interfacial optimization,which provided a new idea for the design of dual-channel H_(2)O_(2) production photocatalysts.
基金supported by the National Natural Science Foundation of China(52372201,52125202,52202247)the Natural Science Foundation of Jiangsu Province(1192261031693)the Fundamental Research Funds for the Central Universities(30919011110,1191030558)。
文摘The molybdenum carbide(Mo_(2)C)has been regarded as one of the most cost-efficient and stable electrocatalyst for the hydrogen evolution reaction(HER)by the virtue of its Pt-like electronic structures.However,the inherent limitation of high density of empty valence band significantly reduces its catalytic reactivity by reason of strong hydrogen desorption resistance.Herein,we propose a multiscale confinement synthesis method to design the nitrogen-rich Mo_(2)C for modulating the band structure via decomposing the pre-coordination bonded polymer in a pressure-tight tube sealing system.Pre-bonded c/N-Mo in the coordination precursor constructs a micro-confinement space,enabling the homogeneous nitrogenization in-situ happened during the formation of Mo_(2)C.Simultaneously,the evolved gases from the precursor decomposition in tube sealing system establish a macro-confinement environment,preventing the lattice N escape and further endowing a continuous nitridation.Combining the multiscale confinement effects,the nitrogen-rich Mo2C displays as high as 25%N-Mo concentration in carbide lattice,leading to a satisfactory band structure.Accordingly,the constructed nitrogen-rich Mo_(2)C reveals an adorable catalytic activity for HER in both alkaline and acid solution.It is anticipated that the multiscale confinement synthesis strategy presents guideline for the rational design of electrocatalysts and beyond.
基金financially supported by the National Natural Science Foundation of China(22179072,22002070)the Natural Science Foundation of Shandong Province(ZR2021QF006)+3 种基金the Outstanding Youth Science Foundation of Shandong Province(Overseas)(2022HWYQ-006)the Natural Science Foundation of Shandong Province(ZR2020QB059)the Fundamental Research Center of Artificial Photosynthesis(FReCAP)financially supported by the National Natural Science Foundation of China(22088102)the China Postdoctoral Science Foundation(No.2022M711898)。
文摘Lead(Pb)-free halide perovskites have recently attracted increasing attention as potential catalysts for CO_(2) photoreduction to CO due to their potential to capture solar energy and drive catalytic reaction.However,issues of the poor charge transfer still remain one of the main obstacles limiting their performance due to the overwhelming radiative and nonradiative charge-carrier recombination losses.Herein,Pb-free Sb-alloyed all-inorganic quadruple perovskite Cs_(4)Mn(Bi_(1-x)Sb_(x))_(2)Cl_(12)(0≤x≤1)is synthesized as efficient photocatalyst.By Sb alloying,the undesired relaxation of photogenerated electrons from conduction band to emission centers of[MnCl6]^(4-)is greatly suppressed,resulting in a weakened PL emission and enhanced charge transfer for photocatalyst.The ensuing Cs_(4)Mn(Bi_(1-x)Sb_(x))_(2)Cl_(12) photocatalyst accomplishes efficient conversion of CO_(2)into CO,accompanied by a surprising production of H_(2)O_(2),a high valueadded product associated with water oxidation.By optimizing Sb^(3+) concentration,a high CO evolution rate of 35.1μmol g^(-1)h^(-1)is achieved,superior to most other Pb and Pb-free halide perovskites.Our findings provide new insights into the mixed-cation alloying strategies for improved photocatalytic performance of Pb-free perovskites and shed light on the rational design of robust band structure toward efficient energy transfer.
基金supported by the National Natural Science Foundation of China(21273124,21290190,21290191 and 91333202)the Innovative Research Groups of the National Science Foundation of China(21421064)the National Basic Research Program of China(2013CB933503 and 2015CB655002)
文摘Organic semiconductors are inherently soft,making it possible to increase their mobilities by strains.Such a unique feature can be exploited directly in flexible electronics for improved device performance.The 2,7-dioctyl[1]benzothieno[3,2-b][1]-benzothiophene derivative,C8-BTBT is one of the best small-molecule hole transport materials.Here,we demonstrated its band structure modulation under strains by combining the non-equilibrium molecular dynamics simulations and first-principles calculations.We found that the C8-BTBT lattice undergoes a transition from monoclinic to triclinic crystal system at the temperature below 160 K.Both shear and uniaxial strains were applied to the low-temperature triclinic phase of C8-BTBT,and polymorphism was identified in the shear process.The band width enhancement is up to 8%under 2%of compressive strain along the x direction,and 14%under 4%of tensile strain along the y direction.The band structure modulation of C8-BTBT can be well related to its herringbone packing motifs,where the edge to face and edge to edge pairs constitute two-dimensional charge transport pathways and their electronic overlaps determine the band widths along the two directions respectively.These findings pave the way for utilizing strains towards improved performance of organic semiconductors on flexible substrates,for example,by bending the substrates.
文摘We present the characteristics of a full-WDM-band photodiode module in 40 Gb/s U-band operation using a Raman amplifier. This module is suitable for wide-band transmission systems with the additional new channels in the U band.
基金supported by the National Natural Science Foundation of China(U21A2076,62274018,52462031)The S&T Program of Hebei(24464401D)+3 种基金The Central Guidance on Local Science and Technology Development Fund of Hebei Province(226Z4305G)Hebei Province Higher Education Science and Technology Research Project(JZX2024030)Shijiazhuang Basic Research Project at Hebei-based Universities(241790847A)The Natural Science Foundation of Hebei Province(E2024202086,E2024202300).
文摘Labor-intensive,trial-and-error methods are frequently employed for modifying the perovskite surface to mitigate trap defects.There is an urgent need for rationally designed and efficient molecular passivators.To address the performance and stability challenges caused by defects in polycrystalline perovskite,we have rationally designed and tailored passivation molecules,4-(trifluoromethyl)benzoic anhydride(TFBA),ethyl 4-(trifluoromethyl)benzoate(TFB),and 4-(trifluoromethyl)benzoic acid(PTF),to minimize interfacial energy loss and modulate the bandgap alignment for achieving efficient perovskite solar cells(PSCs).These molecules could target the perovskite surface defects,particularly Pb-I antisite defects,with the-COOH and trifluoromethyl functional groups at the edges.Among them,PTF exhibited superior passivation performance by coordinat-ing its carboxyl group withPb2+,effectively suppressing non-radiative recombination.Additionally,the fluorine sites in these molecules corrected lattice distortions and stabilized the perovskite structure through hydrogen bonding with MA/FA cations,reducing ion migration,and enhancing moisture resistance.As a result,PTF-modified PSCs achieved an efficiency of 25.57%and maintained over 85%of their initial efficiency after 1600 h of aging.This study provides a clear pathway for optimizing passivation strategies through rational molecular design.
基金supported by National Key Research and Development Program of China(2023YFA1406900)Strategic Priority Research Program(B)of Chinese Academy of Sciences(XDB0580000,XDB43010200,GJ0090406)+7 种基金National Natural Science Foundation of China(62222514,62350073,U2341226,61991440,12227901)Shanghai Science and Technology Committee(23ZR1482000,22JC1402900)Natural Science Foundation of Zhejiang Province(LR22F050004)Shanghai Municipal Science and Technology Major Project(2019SHZDZX01)Youth Innovation Promotion Association(Y2021070)International Partnership Program(112GJHZ2022002FN)of Chinese Academy of SciencesShanghai Human Resources and Social Security Bureau(2022670)China Postdoctoral Science Foundation(2023T160661,2022TQ0353and 2022M713261).
文摘In the domain of spectroscopy,miniaturization efforts often face significant challenges,particularly in achieving high spectral resolution and precise construction.Here,we introduce a computational spectrometer powered by a nonlinear photonic memristor with a WSe2 homojunction.This approach overcomes traditional limitations,such as constrained Fermi level tunability,persistent dark current,and limited photoresponse dimensionality through dynamic energy band modulation driven by palladium(Pd)ion migration.The critical role of Pd ion migration is thoroughly supported by first-principles calculations,numerical simulations,and experimental verification,demonstrating its effectiveness in enhancing device performance.Additionally,we integrate this dynamic modulation with a specialized nonlinear neural network tailored to address the memristor's inherent nonlinear photoresponse.This combination enables our spectrometer to achieve an exceptional peak wavelength accuracy of o.18 nm and a spectral resolution of 2 nm within the 630-640 nm range.This development marks a significant advancement in the creation of compact,high-effciency spectroscopic instruments and offers a versatile platform for applications across diverse material systems.
基金funding support of National Key Research and Development Program of China(Grant No.2022YFB3803900)funding support from Hebei Provincial Department of Science and Technology(236Z4403G,246Z4401G)+3 种基金Research Innovation Team Project of Hebei University(150000321008)Science Research Project of Hebei Education Department(Grant No.JZX2024008)supported by the Research Platform of Material Genome and the Synergic Extreme Condition User Facility in Huairou,Beijing Chinaalso supported by the Engineering Research Center of Zero-carbon Energy Buildings and Measurement Techniques,Ministry of Education。
文摘High-strength high-performance p-type(Bi,Sb)_(2)Te_(3)are of pivotal importance for near-room-temperature thermoelectric conversions,the reliable synthesis and fabrication has been viewed of imperative priority.It is known that the energy-favorable formation of anti-site Sb_(Te)’and vacancy v_(Sb)'''acceptor defects from high-temperature syntheses results in additional charge carriers and scattering centers for electrical and phonon transport.However,how p-type(Bi,Sb)_(2)Te_(3)with minimal lattice defects function remains to be scrutinized.Herein,we present the synergistic enhancements of mechanical robustness and thermoelectric property in crystallographic-defect-suppressed pristine(Bi,Sb)_(2)TeBi_(2)Te_(3)through a simple mechanical alloying combined with spark-plasma-sintering(SPS)process.The Sb_(Te)’and v_(Sb)'''acceptor defects were efficiently restrained,contributing to markedly increased charge carrier mobilities.A slightly enlarged band gap of 0.24 eV underpinned enhanced thermoelectric performance for pristine Bi_(0.3)Sb_(1.7)Te_(3)over a wide temperature range,delivering high zT300 K of 1.16 and zT_(ave)of 1.21 over 300-473 K.Interestingly,the confined in-situ grain coarsening during SPS with uniform dispersive nanopores readily endowed an ultra-high compressive strength of 206 MPa,surpassing that of reported(Bi,Sb)_(2)Te_(3)so far.A 7-pair module(coupled with n-Bi_(2)Te_(3))was fabricated,demonstrating a competitiveΔT over 70 K at T_(hot)=300 K.Furthermore,a power-generation module coupled with n-Mg_(3)SbBi registered a cutting-edge thermoelectric conversion efficiency of 9.5%at a temperature gradient of 250 K.The strategy eliminates the need of complex processing nor extrinsic doping for pristine(Bi,Sb)_(2)Te_(3),demonstrating great potentials in thermoelectric power generation and cooling applications.
基金National Natural Science Foundation of China(12404396,92150101,52225207,52350001)China Postdoctoral Science Foundation(2024M751932)Postdoctoral Fellowship Program of CPSF(GZB20240418)。
文摘Element doping can break the crystal symmetry and realize the topological phase transition in quantum materials,which enables the precise modulation of energy band structure and microscopic dynamical interaction.Herein,we have studied the ultrafast photocarrier dynamics in Zn-doped 3D topological Dirac semimetal Cd_(3)As_(2)utilizing time-resolved optical pump-terahertz probe spectroscopy.Comparing to the pristine Cd_(3)As_(2),we found that the relaxation time of the lightly doped alloy is slightly shorter,while that of the heavily doped alloy exhibits a significant prolongation.Pump-fluence-and temperature-dependent transient terahertz spectroscopy indicated that in pristine and lightly doped samples within nontrivial semimetal phase,the photocarrier dynamics are dominated by the cooling of Dirac fermions.In heavily doped alloy,however,the observed longer relaxation process can be attributed to interband electron-hole recombination,which is a result of doping-induced transition into a trivial semiconductor phase.Our investigation highlights that Zn-doping is an effective and flexible scheme for engineering the electronic structure and transient carrier relaxation dynamics in Cd_(3)As_(2),and offers a control knob for functional switching between diverse optoelectronic devices within the realm of practical applications.
基金supported by the National Natural Science Foundation of China (21971085)the Natural Science Foundation of Shandong Province (ZR2021MB008)the Jinan City “New University 20” Project (202228113)。
文摘The major impediment to the additional industrialization of water splitting is the high cost of the co-catalyst made of noble metals and the sacrificial reagent. A binary photocatalytic system, consisting of B-doped g-C_(3)N_(4) nanosheets(Cu_(20)@BCN-X) and atomically accurate copper clusters, is designed in this study. The copper clusters serve as co-catalysts for H_(2) evolution and exhibit Pt-like activity, whereas the nanosheets serve as carriers and semiconductor components for O_(2) evolution. Such binary system, created using simple techniques, demonstrates hydrogen bonding interactions that promote synergistic effects and efficient binding and charge transfer across the interface between the two components. Band position manipulation of carbon nitride nanosheets demonstrates a Z-scheme charge transfer mechanism between the nanosheets and copper clusters. This photocatalytic system can accomplish the photocatalytic overall water splitting process(259.9 μmol g^(-1)h^(-1)of H_(2) and 129.4 μmol g^(-1)h^(-1)of O_(2)) without using sacrificial agents or noble metal co-catalysts. This work lays the foundation for the design of overall water splitting catalysts by precisely manipulating the energy levels, and it also paves the way for commercialized photocatalytic catalysts that do not require noble metals or sacrificial chemicals.
基金This study was also supported by the European Commission Interreg V France-Wallonie-Vlaanderen project“DepollutAir.”Yang Ding is grateful for the financial support of the China Scholarship Council(201808310127)This study was financially supported by the National Natural Science Foundation of China(U20A20122)+1 种基金the Program for Changjiang Scholars and Innovative Research Team in University(IRT_15R52)of the Chinese Ministry of Education,the Program of Introducing Talents of Discipline to Universities-Plan 111(Grant No.B20002)the Ministry of Science and Technology and the Ministry of Education of China,and the National Key R&D Program of China(2016YFA0202602).
文摘The introduction of vacancy defects in semiconductors has been proven to be a highly effective approach to improve their photocatalytic activity owing to their advantages of promoting light absorption,facilitating photogenerated carrier separation,optimizing electronic structure,and enabling the production of reactive radicals.Herein,we outline the state-of-the-art vacancy-engineered photocatalysts in various applications and reveal how the vacancies influence photocatalytic performance.Specifically,the types of vacancy defects,the methods for tailoring vacancies,the advanced characteri-zation techniques,the categories of photocatalysts with vacancy defects,and the corresponding photocatalytic behaviors are presented.Meanwhile,the methods of vacancies creation and the related photocatalytic performance are correlated,which can be very useful to guide the readers to quickly obtain in-depth knowledge and to have a good idea about the selection of defect engineering methods.The precise characterization of vacancy defects is highly challenging.This review describes the accurate use of a series of characterization techniques with detailed comments and suggestions.This represents the uniqueness of this comprehensive review.The challenges and development prospects in engineering photocatalysts with vacancy defects for practical applications are discussed to provide a promising research direction in this field.
基金Project supported by the National Natural Science Foundation of China(Nos.61527815,31500800,61501426,61471342)the National Key Basic Research Plan(No.2014CB744600)+1 种基金the Beijing Science and Technology Plan(No.Z141100000214002)the Chinese Academy of Sciences’Key Project(No.KJZD-EW-L11-2)
文摘Facing the body＇s EEG（electroencephalograph, 0.5–100 Hz, 5–100 μV） and ECG＇s（electrocardiogram,〈 100 Hz, 0.01–5 mV） micro signal detection requirement, this paper develops a pervasive application micro signal detection ASIC chip with the chopping modulation/demodulation method. The chopper-stabilization circuit with the RRL（ripple reduction loop） circuit is to suppress the ripple voltage, which locates at the single-stage amplifier＇s outputting terminal. The single-stage chopping core＇s noise has been suppressed too, and it is beneficial for suppressing noises of post-circuit. The chopping core circuit uses the PFB（positive feedback loop） to increase the inputting resistance, and the NFB（negative feedback loop） to stabilize the 40 dB intermediate frequency gain. The cascaded switch-capacitor sample/hold circuit has been used for deleting spike noises caused by non-ideal MOS switches, and the VGA/BPF（voltage gain amplifier/band pass filter） circuit is used to tune the chopper system＇s gain/bandwidth digitally. Assisted with the designed novel dry-electrode, the real test result of the chopping amplifying circuit gives some critical parameters： 8.1 μW/channel, 0.8 μVrms（@band-widthD100 Hz）, 4216–11220 times digitally tuning gain range, etc. The data capture system uses the NI CO＇s data capturing DAQmx interface,and the captured micro EEG/ECG＇s waves are real-time displayed with the PC-Labview. The proposed chopper system is a unified EEG/ECG signal＇s detection instrument and has a critical real application value.
