Electrochemical reduction of nitrate(NO_(3^(-)))serves as an eco-friendly friendly alternative to the conventional Haber-Bosch ammonia(NH_(3))synthesis process.The Cu electrocatalyst is widely recognized for its stron...Electrochemical reduction of nitrate(NO_(3^(-)))serves as an eco-friendly friendly alternative to the conventional Haber-Bosch ammonia(NH_(3))synthesis process.The Cu electrocatalyst is widely recognized for its strong adsorption capacity towards nitrate,but its limited H adsorption and slow hydrogenation of oxynitride intermediates hinder the efficiency of converting NO_(3^(-))into NH_(3).Herein,a series of nanocomposite catalysts composed of CuO nanostructure with low NiO content that grow in-situ on carbon paper(Cu O/Ni O_(x)-CP)were synthesized via hydrothermal method and calcination for enhanced nitrate electroreduction utilizing the strong nitrate adsorption capacity of copper and excellent water dissociation ability of NiO to supply hydrogen free radicals(·H).In-situ Raman spectroscopy reveals dynamic reconstruction of Cu/NiO_(x)during the electrochemical nitrate reduction process from Cu O/NiO_(x).Due to the synergistic effect of Cu and NiO,a high Faradaic efficiency(FE,~97.9%)and yield rate(YR,391.5μmol h^(-1)cm^(-2))of ammonia are achieved on CuO/NiO_(2.3%)-CP.Electron paramagnetic resonance(EPR)proves that the presence of Ni O enhances the generation of·H,which can be rapidly consumed during nitrate reduction process.Density functional theory(DFT)calculations indicate that the activation energy of Ni O(0.57 eV)is much lower than Cu(0.84 e V)for water splitting to generate·H,thus facilitating*NO hydrogenations.This drives us to create more effective catalysts for nitrate reduction under neutral conditions by promoting H2O dissociation.展开更多
Transition metal Ni anchored in carbon material represents outstanding 2e^(-) oxygen reduction reaction(ORR)catalytic selectivity,but enhancing the adsorption strength of intermediate*OOH to promote its selectivity re...Transition metal Ni anchored in carbon material represents outstanding 2e^(-) oxygen reduction reaction(ORR)catalytic selectivity,but enhancing the adsorption strength of intermediate*OOH to promote its selectivity remains a major challenge.Herein,the NiX/Ni@NCHS composite catalyst with heteroatom doping(O,S)is modulated by controlling partial pyrolysis strategies on honeycomb-like porous carbon to manipulate the electronic structure of the metal Ni.With the synergistic effect of honeycomb structure and O atom,NiO/Ni@NCHS-700 exhibits an exceptional H_(2)O_(2)selectivity of above 89.1%across a wide potential range from 0.1 to 0.6 V in an alkaline electrolyte,and an unexpected H_(2)O_(2)production rate up to 1.47 mol gcat^(-1) h^(-1)@0.2 V,which outperforms most of the state-of-the-art catalyst.Meanwhile,NiS/Ni@NCHS exhibits excellent electrocatalytic performance,with 2e^(-) ORR selectivity of 91.3%,H_(2)O_(2)yield of 1.85@0.3 V.Density functional theory simulations and experiments results reveal that the heteroatom doping(O,S)method has been employed to regulate the adsorption strength of Ni atoms with*OOH,and combined with the self-sacrificing template-assisted pyrolysis approach to improve the microstructure of catalysts and optimize the active site.The heteroatom doping method in this work provides significant guidance for promoting 2e^(-) ORR electrocatalysis to produce H_(2)O_(2).展开更多
Modulating the adsorption energy of intermediate species via alloying presents a promising approach to enhance the electrocatalytic nitrate reduction to ammonia(NRA).Nonetheless,the synthesis of alloy catalysts that a...Modulating the adsorption energy of intermediate species via alloying presents a promising approach to enhance the electrocatalytic nitrate reduction to ammonia(NRA).Nonetheless,the synthesis of alloy catalysts that are uniformly distributed and structurally stable poses significant challenges.Herein,the CuNi alloy was successfully anchored on oxygen vacancy-rich N-Ti_(3)C_(2)T_(x) through metal-support interactions(MSI).The three-dimensional(3D)wrinkled morphology of N-Ti_(3)C_(2)T_(x) MXene was achieved by employing melamine-formaldehyde spheres(MFs)as self-sacrificial templates,which effectively prevented the restacking of the Ti_(3)C_(2)T_(x) layers,thereby increasing specific surface area and promoting the formation of surface oxygen vacancies.Ti–O–M structure plays a crucial role in inhibiting both particle migration and metal atom diffusion.X-ray photoelectron spectroscopy(XPS)analysis confirms moderate metal-support interactions between the CuNi alloy and N-Ti_(3)C_(2)T_(x),leading to the establishment of stable Ti–O–M bonds and charge redistribution within the Ti-O-M framework.The Cu_(5)Ni_(5)/N-Ti_(3)C_(2)T_(x) sample achieves an impressive Faradaic efficiency(FE)of 97.50%at−0.27 V vs.RHE,alongside the highest NH3 yield rate of 527.44µmol h−1 cm−2.In-situ electrochemical Raman spectroscopy and theoretical calculations reveal that the high intrinsic catalytic activity of NRA can be attributed to the synergistic effects between the CuNi alloy and the interfacial metal-oxygen interactions.This work provides significant perspectives on the design of interfacial metal interactions and the development of durable electrocatalysts.展开更多
Ultrahigh pressure technique remarkably extends solid solubility limitation of Al alloying element(~25 at.%)in Mg alloys,resulting in unique solid-solution strengthening and age hardening response.Microhardness,yield ...Ultrahigh pressure technique remarkably extends solid solubility limitation of Al alloying element(~25 at.%)in Mg alloys,resulting in unique solid-solution strengthening and age hardening response.Microhardness,yield strength and ultimate compressive strength are improved simultaneously without degrading plasticity by forming homogeneous and globular-shaped Mg17Al12 precipitates of 10e30 nm.In addition,thermal resistance is enhanced by eliminating the dominant growth of(101)plane and anchoring dense stacking faults in phase interface.展开更多
基金supported by the National Natural Science Foundation of China(No.U22A20253)。
文摘Electrochemical reduction of nitrate(NO_(3^(-)))serves as an eco-friendly friendly alternative to the conventional Haber-Bosch ammonia(NH_(3))synthesis process.The Cu electrocatalyst is widely recognized for its strong adsorption capacity towards nitrate,but its limited H adsorption and slow hydrogenation of oxynitride intermediates hinder the efficiency of converting NO_(3^(-))into NH_(3).Herein,a series of nanocomposite catalysts composed of CuO nanostructure with low NiO content that grow in-situ on carbon paper(Cu O/Ni O_(x)-CP)were synthesized via hydrothermal method and calcination for enhanced nitrate electroreduction utilizing the strong nitrate adsorption capacity of copper and excellent water dissociation ability of NiO to supply hydrogen free radicals(·H).In-situ Raman spectroscopy reveals dynamic reconstruction of Cu/NiO_(x)during the electrochemical nitrate reduction process from Cu O/NiO_(x).Due to the synergistic effect of Cu and NiO,a high Faradaic efficiency(FE,~97.9%)and yield rate(YR,391.5μmol h^(-1)cm^(-2))of ammonia are achieved on CuO/NiO_(2.3%)-CP.Electron paramagnetic resonance(EPR)proves that the presence of Ni O enhances the generation of·H,which can be rapidly consumed during nitrate reduction process.Density functional theory(DFT)calculations indicate that the activation energy of Ni O(0.57 eV)is much lower than Cu(0.84 e V)for water splitting to generate·H,thus facilitating*NO hydrogenations.This drives us to create more effective catalysts for nitrate reduction under neutral conditions by promoting H2O dissociation.
文摘Transition metal Ni anchored in carbon material represents outstanding 2e^(-) oxygen reduction reaction(ORR)catalytic selectivity,but enhancing the adsorption strength of intermediate*OOH to promote its selectivity remains a major challenge.Herein,the NiX/Ni@NCHS composite catalyst with heteroatom doping(O,S)is modulated by controlling partial pyrolysis strategies on honeycomb-like porous carbon to manipulate the electronic structure of the metal Ni.With the synergistic effect of honeycomb structure and O atom,NiO/Ni@NCHS-700 exhibits an exceptional H_(2)O_(2)selectivity of above 89.1%across a wide potential range from 0.1 to 0.6 V in an alkaline electrolyte,and an unexpected H_(2)O_(2)production rate up to 1.47 mol gcat^(-1) h^(-1)@0.2 V,which outperforms most of the state-of-the-art catalyst.Meanwhile,NiS/Ni@NCHS exhibits excellent electrocatalytic performance,with 2e^(-) ORR selectivity of 91.3%,H_(2)O_(2)yield of 1.85@0.3 V.Density functional theory simulations and experiments results reveal that the heteroatom doping(O,S)method has been employed to regulate the adsorption strength of Ni atoms with*OOH,and combined with the self-sacrificing template-assisted pyrolysis approach to improve the microstructure of catalysts and optimize the active site.The heteroatom doping method in this work provides significant guidance for promoting 2e^(-) ORR electrocatalysis to produce H_(2)O_(2).
基金upported by the National Natural Science Foundation of China(Nos.U22A20253,52272293,and 52401275)the Fellowship of China Postdoctoral Science Foundation(No.2021M701116).
文摘Modulating the adsorption energy of intermediate species via alloying presents a promising approach to enhance the electrocatalytic nitrate reduction to ammonia(NRA).Nonetheless,the synthesis of alloy catalysts that are uniformly distributed and structurally stable poses significant challenges.Herein,the CuNi alloy was successfully anchored on oxygen vacancy-rich N-Ti_(3)C_(2)T_(x) through metal-support interactions(MSI).The three-dimensional(3D)wrinkled morphology of N-Ti_(3)C_(2)T_(x) MXene was achieved by employing melamine-formaldehyde spheres(MFs)as self-sacrificial templates,which effectively prevented the restacking of the Ti_(3)C_(2)T_(x) layers,thereby increasing specific surface area and promoting the formation of surface oxygen vacancies.Ti–O–M structure plays a crucial role in inhibiting both particle migration and metal atom diffusion.X-ray photoelectron spectroscopy(XPS)analysis confirms moderate metal-support interactions between the CuNi alloy and N-Ti_(3)C_(2)T_(x),leading to the establishment of stable Ti–O–M bonds and charge redistribution within the Ti-O-M framework.The Cu_(5)Ni_(5)/N-Ti_(3)C_(2)T_(x) sample achieves an impressive Faradaic efficiency(FE)of 97.50%at−0.27 V vs.RHE,alongside the highest NH3 yield rate of 527.44µmol h−1 cm−2.In-situ electrochemical Raman spectroscopy and theoretical calculations reveal that the high intrinsic catalytic activity of NRA can be attributed to the synergistic effects between the CuNi alloy and the interfacial metal-oxygen interactions.This work provides significant perspectives on the design of interfacial metal interactions and the development of durable electrocatalysts.
基金We greatly acknowledge the financial support from NSFC(no.51771162,51422105)National Key Research and Development Program(2017YFB0702001)Distinguished Youth Foundation of Hebei Province(E2015203404).
文摘Ultrahigh pressure technique remarkably extends solid solubility limitation of Al alloying element(~25 at.%)in Mg alloys,resulting in unique solid-solution strengthening and age hardening response.Microhardness,yield strength and ultimate compressive strength are improved simultaneously without degrading plasticity by forming homogeneous and globular-shaped Mg17Al12 precipitates of 10e30 nm.In addition,thermal resistance is enhanced by eliminating the dominant growth of(101)plane and anchoring dense stacking faults in phase interface.
