Aqueous zinc(Zn)-ion batteries(AZIBs)have gained significant interest in energy storage due to several unique advantages.Utilizing waterbased electrolytes enhances environmental sustainability,while the abundance and ...Aqueous zinc(Zn)-ion batteries(AZIBs)have gained significant interest in energy storage due to several unique advantages.Utilizing waterbased electrolytes enhances environmental sustainability,while the abundance and affordability of Zn offer economic benefits.Manganese(Mn)-based materials,commonly used as cathodes in these batteries,provide high theoretical capacity,high electrical conductivity,and good structural stability.However,these materials suffer from capacity degradation over repeated cycles due to structural collapse and limited conductivity.To address this problem,we synthesized a magnesium(Mg)-and Mn-based composite,Mg^(2+)-Mn_(3)O_(4),using the hydrothermal method with an optimized amount of ammonium hydroxide(NH_(4)OH)solution.This approach effectively stabilizes the structure during cycling,enhancing both capacity retention and conductivity.The Zn^(2+)/H+intercalation/deintercalation process was confirmed by experimental results and ex-situ X-ray diffraction analysis,which demonstrates that Mg^(2+),along with optimized NH_(4)OH amount,prevents structural collapse and improves conductivity.Under optimal process conditions,the composite electrode(Mg^(2+)-Mn_(3)O_(4)–8 ml)achieved a capacity of 173.58 mA h g^(-1) at 0.5 A g^(-1),with excellent rate performance of 71.39 mA h g^(-1) at 10 A g^(-1).Remarkably,even at 5 A g^(-1),the electrode maintained a capacity of 86.87 mA h g^(-1) over 2100 cycles,underscoring the role of Mg^(2+)and NH_(4)OH in enhancing the reversible insertion/extraction stability of Zn^(2+)in Mn-based layered materials.This study presents a novel strategy for metal-ion incorporation in Mn-based AZIBs,offering insights into the optimization of cathode materials and advancing research on associated storage mechanisms.展开更多
Photocatalytic H_(2) production from an aqueous NH_(3) solution is an emerging and potential way to pu-rify wastewater and obtain green energy.However,the H_(2) production rate by semiconductors is largely limited by ...Photocatalytic H_(2) production from an aqueous NH_(3) solution is an emerging and potential way to pu-rify wastewater and obtain green energy.However,the H_(2) production rate by semiconductors is largely limited by the fast recombination of photogenerated charges and the weak H+adsorption ability.Herein,non-noble bimetallic CuNi cocatalyst was deposited on the surface of TiO_(2) nanofiber to prepare CuNi/TiO_(2) composites via simple hydrothermal procedure followed by calcination treatment.The obtained CuNi/TiO_(2) composites not only improve the absorption and utilization abilities of incident light,but also offer plen-tiful active sites and inhibit the recombination of charges.As a result,the photocatalytic efficiency of H_(2) production is much higher than that of pure TiO_(2) in low concentration ammonia solution.Particularly,the Cu_(2) Ni_(1)/TiO_(2) sample exhibits the maximum H_(2) production rate(285.4μmol h^(-1) g^(-1)),which was 4.0,2.1 and 6.7 times higher than that of Cu/TiO_(2),Ni/TiO_(2) and pure TiO_(2) nanofiber,respectively.This yield also outperforms Pt/TiO_(2) in terms of its performance.Meanwhile,the oxidation product of hydrazine hydrate is detected.Furthermore,density-functional-theory(DFT)calculations reveal that the synergistic effect of bimetallic CuNi alloy benefits to H^(∗)sorption and promotes H_(2) desorption,thus resulting in the improvement of H_(2) production.This work provides new insight into the fabrication of non-noble metal alloys as efficient cocatalysts for photocatalysis.展开更多
Formaldehyde(HCHO)is a significant indoor pollutant found in various sources and poses potential health risks to humans.Noble metal catalysts show efficient and stable catalytic activity for ambient-temperature HCHO o...Formaldehyde(HCHO)is a significant indoor pollutant found in various sources and poses potential health risks to humans.Noble metal catalysts show efficient and stable catalytic activity for ambient-temperature HCHO oxidation,yet suffer from low metal utilization.Efforts focus on designing catalysts with enhanced intrinsic activity and reduced noble metal loading.In this study,we developed a simple pretreatment method using ammonia solution on SiO_(2)carrier to enhance the activity of the Pd/SiO_(2)catalyst for HCHO oxidation.After the carrier was pretreated with an ammonia solution,a significant promoting effect was observed on the Pd/SiO_(2)(NH_(3)·H_(2)O)-R catalyst.It achieved almost complete oxidation of 150 ppmV of HCHO at 25℃,much better than the Pd/SiO_(2)-R(5%HCHO conversion rate).Multiple characterization results indicated that the ammonia solution pretreatment of the SiO_(2)carrier increased the surface defects,facilitating the anchoring of Pd nanoparticles and increasing their dispersion.The increase dispersion of Pd resulted in the generation of additional oxygen vacancies on the catalyst surfaces.The increased in oxygen vacancies on the catalyst was beneficial for enhancing the catalyst's ability to activate H_(2)O to form surface hydroxyl groups,thereby accelerating the catalytic oxidation process of HCHO.The reaction mechanism of HCHO on the Pd/SiO_(2)(NH_(3)·H_(2)O)-R catalyst mainly follows an efficient pathway:firstly,the HCHO being oxidized by surface active hydroxyl groups to formate;subsequently,the formate being oxidized by hydroxyl groups to H_(2)O and CO_(2).This study provides a promising strategy for designing high-performance noble metal catalysts for HCHO catalytic oxidation.展开更多
基金supported by a National Research Foundation of Korea(NRF)grant funded by the Korean government(MSIT)(No.2018R1A6A1A03025708).
文摘Aqueous zinc(Zn)-ion batteries(AZIBs)have gained significant interest in energy storage due to several unique advantages.Utilizing waterbased electrolytes enhances environmental sustainability,while the abundance and affordability of Zn offer economic benefits.Manganese(Mn)-based materials,commonly used as cathodes in these batteries,provide high theoretical capacity,high electrical conductivity,and good structural stability.However,these materials suffer from capacity degradation over repeated cycles due to structural collapse and limited conductivity.To address this problem,we synthesized a magnesium(Mg)-and Mn-based composite,Mg^(2+)-Mn_(3)O_(4),using the hydrothermal method with an optimized amount of ammonium hydroxide(NH_(4)OH)solution.This approach effectively stabilizes the structure during cycling,enhancing both capacity retention and conductivity.The Zn^(2+)/H+intercalation/deintercalation process was confirmed by experimental results and ex-situ X-ray diffraction analysis,which demonstrates that Mg^(2+),along with optimized NH_(4)OH amount,prevents structural collapse and improves conductivity.Under optimal process conditions,the composite electrode(Mg^(2+)-Mn_(3)O_(4)–8 ml)achieved a capacity of 173.58 mA h g^(-1) at 0.5 A g^(-1),with excellent rate performance of 71.39 mA h g^(-1) at 10 A g^(-1).Remarkably,even at 5 A g^(-1),the electrode maintained a capacity of 86.87 mA h g^(-1) over 2100 cycles,underscoring the role of Mg^(2+)and NH_(4)OH in enhancing the reversible insertion/extraction stability of Zn^(2+)in Mn-based layered materials.This study presents a novel strategy for metal-ion incorporation in Mn-based AZIBs,offering insights into the optimization of cathode materials and advancing research on associated storage mechanisms.
基金financially supported by the National Natural Science Foundation of China(Nos.22108211,22478308,22478309,22272125,22402156,and 22409151)the Research and Innovation Initiatives of WHPU(No.2024Y18)the Key Research and De-velopment Project of Hainan Province(No.ZDYF2024GXJS005).
文摘Photocatalytic H_(2) production from an aqueous NH_(3) solution is an emerging and potential way to pu-rify wastewater and obtain green energy.However,the H_(2) production rate by semiconductors is largely limited by the fast recombination of photogenerated charges and the weak H+adsorption ability.Herein,non-noble bimetallic CuNi cocatalyst was deposited on the surface of TiO_(2) nanofiber to prepare CuNi/TiO_(2) composites via simple hydrothermal procedure followed by calcination treatment.The obtained CuNi/TiO_(2) composites not only improve the absorption and utilization abilities of incident light,but also offer plen-tiful active sites and inhibit the recombination of charges.As a result,the photocatalytic efficiency of H_(2) production is much higher than that of pure TiO_(2) in low concentration ammonia solution.Particularly,the Cu_(2) Ni_(1)/TiO_(2) sample exhibits the maximum H_(2) production rate(285.4μmol h^(-1) g^(-1)),which was 4.0,2.1 and 6.7 times higher than that of Cu/TiO_(2),Ni/TiO_(2) and pure TiO_(2) nanofiber,respectively.This yield also outperforms Pt/TiO_(2) in terms of its performance.Meanwhile,the oxidation product of hydrazine hydrate is detected.Furthermore,density-functional-theory(DFT)calculations reveal that the synergistic effect of bimetallic CuNi alloy benefits to H^(∗)sorption and promotes H_(2) desorption,thus resulting in the improvement of H_(2) production.This work provides new insight into the fabrication of non-noble metal alloys as efficient cocatalysts for photocatalysis.
基金supported by the Sanming University(No.23YG05)the Science Foundation of Fujian Province(No.2023J011027).
文摘Formaldehyde(HCHO)is a significant indoor pollutant found in various sources and poses potential health risks to humans.Noble metal catalysts show efficient and stable catalytic activity for ambient-temperature HCHO oxidation,yet suffer from low metal utilization.Efforts focus on designing catalysts with enhanced intrinsic activity and reduced noble metal loading.In this study,we developed a simple pretreatment method using ammonia solution on SiO_(2)carrier to enhance the activity of the Pd/SiO_(2)catalyst for HCHO oxidation.After the carrier was pretreated with an ammonia solution,a significant promoting effect was observed on the Pd/SiO_(2)(NH_(3)·H_(2)O)-R catalyst.It achieved almost complete oxidation of 150 ppmV of HCHO at 25℃,much better than the Pd/SiO_(2)-R(5%HCHO conversion rate).Multiple characterization results indicated that the ammonia solution pretreatment of the SiO_(2)carrier increased the surface defects,facilitating the anchoring of Pd nanoparticles and increasing their dispersion.The increase dispersion of Pd resulted in the generation of additional oxygen vacancies on the catalyst surfaces.The increased in oxygen vacancies on the catalyst was beneficial for enhancing the catalyst's ability to activate H_(2)O to form surface hydroxyl groups,thereby accelerating the catalytic oxidation process of HCHO.The reaction mechanism of HCHO on the Pd/SiO_(2)(NH_(3)·H_(2)O)-R catalyst mainly follows an efficient pathway:firstly,the HCHO being oxidized by surface active hydroxyl groups to formate;subsequently,the formate being oxidized by hydroxyl groups to H_(2)O and CO_(2).This study provides a promising strategy for designing high-performance noble metal catalysts for HCHO catalytic oxidation.
