NaBH_(4) was widely regarded as a low-cost hydrogen storage material due to its high-mass hydrogen capacity of approximately 10.8%(mass)and high volumetric hydrogen capacity of around 115 g·L^(–1).However,it exh...NaBH_(4) was widely regarded as a low-cost hydrogen storage material due to its high-mass hydrogen capacity of approximately 10.8%(mass)and high volumetric hydrogen capacity of around 115 g·L^(–1).However,it exhibits strong stability and requires temperatures above 500℃ for hydrogen release in practical applications.In this study,two polyhydric alcohols,xylitol and erythritol(XE),were prepared as a binary eutectic sugar alcohol through a grinding-melting method.This binary eutectic sugar alcohol was used as a proton-hydrogen carrier to destabilize NaBH_(4).The 19NaBH_(4)-16XE composite material prepared by ball milling could start releasing hydrogen at 57.5℃,and the total hydrogen release can reach over 88.8%(4.45%(mass))of the theoretical capacity.When the 19NaBH_(4)-16XE composite was pressed into solid blocks,the volumetric hydrogen capacity of the block-shaped composite could reach 67.2 g·L^(–1).By controlling the temperature,the hydrogen desorption capacity of the NaBH_(4)-XE composite material was controllable,which has great potential for achieving solid-state hydrogen production from NaBH_(4).展开更多
Sodium borohydride(NaBH_(4)) is considered as the most potential hydrogen storage material for portable proton exchange membrane fuel cells(PEMFC)because of its high theoretical hydrogen capacity.However,the slow and ...Sodium borohydride(NaBH_(4)) is considered as the most potential hydrogen storage material for portable proton exchange membrane fuel cells(PEMFC)because of its high theoretical hydrogen capacity.However,the slow and poor kinetic stability of hydrogen generation from NaBH_(4) hydrolysis limits its application.There are two main factors influencing the kinetics stability of hydrogen generation from NaBH_(4).One factor is that the alkaline byproducts(NaBO_(2)) of the hydrolysis reaction can increase the pH of the solution,thus inhibiting the reaction process.It mainly happens in the NaBH_(4) solution hydrolysis system.Another factor is that the monotonous increase in reaction temperature leads to uncontrollable and unpredictable hydrolysis rates in the solid NaBH_(4) hydrolysis system.This is due to the excess heat generated from this exothermic reaction in the initial reaction of NaBH_(4) hydrolysis.In this perspective,we summarize the latest research progress in hydrogen generation from NaBH_(4) and emphasize the design principles of catalysts for hydrogen generation from NaBH_(4) solution and solid state NaBH_(4).The importance of carbon as catalyst support material for NaBH_(4) hydrolysis is also highlighted.展开更多
In order to avoid the formation ofηphase(W_(6)Co_(6)C or W_(3)Co_(3)C)that adversely affects the sintering process and its products in the preparation process of ultra-fine WC-Co powder,a technical route of prereduct...In order to avoid the formation ofηphase(W_(6)Co_(6)C or W_(3)Co_(3)C)that adversely affects the sintering process and its products in the preparation process of ultra-fine WC-Co powder,a technical route of prereduction of WO_(3)-Co_(3)O_(4)to WO_(2)-Co and then deep reduction carbonization to WC-Co powder has been proposed.This study mainly investigates the influence of gas partial pressure on the pre-reduction process of WO_(3)-Co_(3)O_(4)under a mixed atmosphere of H_(2)-C_(2)H_(4)-Ar at 600℃and establishes the kinetic equations of pre-reduction and carbon evolution.The results indicate that increasing the partial pressure of hydrogen is conducive to the rapid and complete conversion of WO_(3) to WO_(2).High carbon content can be generated by the deposition of C_(2)H_(4),and it hinders the diffusion of the reducing gas;WO_(3)still cannot be completely reduced to WO_(2)as the partial pressure of C_(2)H_(4) increases to 60%.For the carbon evolution of C_(2)H_(4),the carbon amount is positively related to the H_(2)partial pressure,but it shows the highest amount and evolution rate when the ethylene partial pressure is 20%.Based on the reduction rate curves of WO_(3) and carbon evolution rate curves of C_(2)H_(4),the rate equations of pre-reduction and carbon evolution of WO_(3)-Co_(3)O_(4)system at 600℃are established.The pre-reduction reaction belongs to the first-order reaction,and its equation is expressed as follows:r=-(dw_(WO_(3)))/dt=(9±0.15)×10^(-2)×P_(H_(2))^(0.44)P_(C_(2)H_(4))&(0.57)The carbon deposition rate equation of C_(2)H_(4) can be expressed as follows:r=-(dc_C)/dt=r_f-r_b≌7.35×10^(-2)×P_(C_(2)H_(4))^(0.31)展开更多
Efficient photocatalytic reduction of CO_(2) to high-calorific-value CH4,an ideal target product,is a blueprint for C_(1)industry relevance and carbon neutrality,but it also faces great challenges.Herein,we demonstrat...Efficient photocatalytic reduction of CO_(2) to high-calorific-value CH4,an ideal target product,is a blueprint for C_(1)industry relevance and carbon neutrality,but it also faces great challenges.Herein,we demonstrate unprecedented hybrid SiC photocatalysts modified by Fe-based cocatalyst,which are prepared via a facile impregnation-reduction method,featuring an optimized local electronic structure.It exhibits a superior photocatalytic carbon-based products yield of 30.0μmol g^(−1) h^(−1) and achieves a record CH_(4) selectivity of up to 94.3%,which highlights the effectiveness of electron-rich Fe cocatalyst for boosting photocatalytic performance and selectivity.Specifically,the synergistic effects of directional migration of photogenerated electrons and strongπ-back bonding on low-valence Fe effectively strengthen the adsorption and activation of reactants and intermediates in the CO_(2)→CH_(4) pathway.This study inspires an effective strategy for enhancing the multielectron reduction capacity of semiconductor photocatalysts with low-cost Fe instead of noble metals as cocatalysts.展开更多
The persistent increase of CO_(2) levels in the atmosphere,already exceeding 400 ppm,urges the exploration of CO_(2) emission reduction and recycling technologies.Ideally,photocatalytic conversion of CO_(2) into valua...The persistent increase of CO_(2) levels in the atmosphere,already exceeding 400 ppm,urges the exploration of CO_(2) emission reduction and recycling technologies.Ideally,photocatalytic conversion of CO_(2) into valuable hydrocarbons realizes solar-to-chemical energy conversion,which is a desirable“kill two birds with one stone”strategy;namely,CO_(2) photoreduction can simultaneously tackle energy shortage and keep global carbon balance.Graphitic carbon nitride(g-C_(3)N_(4))working on CO_(2) reduction reaction deserves a highlight not only for the metal-free feature that endows it with low cost,tunable electronic structure,and easy fabrication properties but also because of its strong reduction ability.The present review concisely summarizes the latest advances of g-C_(3)N_(4)-based photocatalysts toward CO_(2) reduction.It starts with the discussion of thermodynamics and dynamics aspects of the CO_(2) reduction process.Then the modification strategies to promote g-C_(3)N_(4)-based photocatalysts in CO_(2) photoreduction have been discussed in detail,including surface functionalization,molecule structure engineering,crystallization,morphology engineering,loading cocatalyst,and constructing heterojunction.Meanwhile,the intrinsic factors affecting CO_(2) reduction activity and selectivity are analyzed and summarized.In the end,the challenges and prospects for the future development of highly g-C_(3)N_(4)-based photocatalysts in CO_(2) reduction are also presented.展开更多
Photocatalytic reduction of CO_(2) is considered as a kind of promising technologies for solving the greenhouse effect.Herein,a novel hybrid structure of g-C_(3)N_(4)/ZnO/Ti_(3)C_(2) photocatalysts was designed and fa...Photocatalytic reduction of CO_(2) is considered as a kind of promising technologies for solving the greenhouse effect.Herein,a novel hybrid structure of g-C_(3)N_(4)/ZnO/Ti_(3)C_(2) photocatalysts was designed and fabricated to investigate their abilities for CO_(2) reduction.As demonstration,heterojunction of g-C_(3)N_(4)/ZnO can improve photogenerated carriers’separation,the addition of Ti_(3)C_(2) fragments can further facilitate the photocatalytic performance from CO_(2) to CO.Hence,g-C_(3)N_(4)/ZnO/Ti_(3)C_(2) has efficiently increased CO production by 8 and 12 times than pristine g-C_(3)N_(4) and ZnO,respectively.Which is ascribed to the photogenerated charge migration promoted by metallic Ti_(3)C_(2).This work provides a guideline for designing efficient hybrid catalysts on other applications in the renewable energy fields.展开更多
The conversion of CO_(2)into value-added chemicals coupled with the storage of intermittent renewable electricity is attractive.CuO nanosheets with an average size and thickness of~30 and~20 nm have been developed,whi...The conversion of CO_(2)into value-added chemicals coupled with the storage of intermittent renewable electricity is attractive.CuO nanosheets with an average size and thickness of~30 and~20 nm have been developed,which are in situ reduced into Cu nanosheets during electrochemical CO_(2)reduction reaction(ECO_(2)RR).The derived Cu nanosheets demonstrate much higher selectivity for C2H4production than commercial CuO derived Cu powder,with an optimum Faradaic efficiency of 56.2%and a partial current density of C_(2)H_(4)as large as 171.0 mA cm^(-2)in a gas diffusion flow cell.The operando attenuated total reflectance-Fourier transform infrared spectra measurements and density functional theory simulations illustrate that the high activity and selectivity of Cu nanosheets originate from the edge sites on Cu nanosheets with a coordinate number around 5(4–6),which facilitates the formation of^(*)CHO rather than^(*)COH intermediate,meanwhile boosting the C-C coupling reaction of^(*)CO and^(*)CHO intermediates,which are the critical steps for C_(2)H_(4)formation.展开更多
Photocatalytic CO_(2)reduction to valuable product exhibit promising prospect for solving the energy crisis and the greenhouse effect.Herein,Co-Ti_(3)C_(2)T_(x)/g-C_(3)N_(4)(Co-TC/CN)composite with enhanced photocatal...Photocatalytic CO_(2)reduction to valuable product exhibit promising prospect for solving the energy crisis and the greenhouse effect.Herein,Co-Ti_(3)C_(2)T_(x)/g-C_(3)N_(4)(Co-TC/CN)composite with enhanced photocatalytic performance for converting CO_(2)to CO and CH_(4)was constructed by electrostatic self-assembly method.The close contact interface between Co-Ti_(3)C_(2)T_(x)and g-C_(3)N_(4)nanosheets can be used as fast transport channels of photogenerated electrons and effectively promote the separation of photogenerated electrons and holes,and the interface between the Co and Ti_(3)C_(2)T_(x)might be the active sites for CO_(2)adsorption and activation.The optimized Co-Ti_(3)C_(2)T_(x)/g-C_(3)N_(4)composite exhibited the highest photocatalytic performance with the CO and CH_(4)production of 55.04 μmol·g^(-1)and 2.29 μmol·g^(-1),respectively,which were 7.5 times and 5.8 times than those of g-C_(3)N_(4).Furthermore,the stability of g-C_(3)N_(4)was improved after coupling with Co-Ti_(3)C_(2)T_(x).展开更多
?β-Unsaturated amides with various substitution pattems at the carbon-carbon double And and nitrogen atom can be reduced to the corresponding saturated amides with high selectivity and yields with NaBH4/BiCl3 system.
基金support from the National Natural Science Foundation of China(52201255)the Natural Science Foundation of Jiangsu Province(BK20210884)the Innovation,and Entrepreneurship Program of Jiangsu Province(JSSCBS20211007).
文摘NaBH_(4) was widely regarded as a low-cost hydrogen storage material due to its high-mass hydrogen capacity of approximately 10.8%(mass)and high volumetric hydrogen capacity of around 115 g·L^(–1).However,it exhibits strong stability and requires temperatures above 500℃ for hydrogen release in practical applications.In this study,two polyhydric alcohols,xylitol and erythritol(XE),were prepared as a binary eutectic sugar alcohol through a grinding-melting method.This binary eutectic sugar alcohol was used as a proton-hydrogen carrier to destabilize NaBH_(4).The 19NaBH_(4)-16XE composite material prepared by ball milling could start releasing hydrogen at 57.5℃,and the total hydrogen release can reach over 88.8%(4.45%(mass))of the theoretical capacity.When the 19NaBH_(4)-16XE composite was pressed into solid blocks,the volumetric hydrogen capacity of the block-shaped composite could reach 67.2 g·L^(–1).By controlling the temperature,the hydrogen desorption capacity of the NaBH_(4)-XE composite material was controllable,which has great potential for achieving solid-state hydrogen production from NaBH_(4).
基金supported by MOST of China(No.2021YFB4000603)NSFC(No.22179002 and 51971004).
文摘Sodium borohydride(NaBH_(4)) is considered as the most potential hydrogen storage material for portable proton exchange membrane fuel cells(PEMFC)because of its high theoretical hydrogen capacity.However,the slow and poor kinetic stability of hydrogen generation from NaBH_(4) hydrolysis limits its application.There are two main factors influencing the kinetics stability of hydrogen generation from NaBH_(4).One factor is that the alkaline byproducts(NaBO_(2)) of the hydrolysis reaction can increase the pH of the solution,thus inhibiting the reaction process.It mainly happens in the NaBH_(4) solution hydrolysis system.Another factor is that the monotonous increase in reaction temperature leads to uncontrollable and unpredictable hydrolysis rates in the solid NaBH_(4) hydrolysis system.This is due to the excess heat generated from this exothermic reaction in the initial reaction of NaBH_(4) hydrolysis.In this perspective,we summarize the latest research progress in hydrogen generation from NaBH_(4) and emphasize the design principles of catalysts for hydrogen generation from NaBH_(4) solution and solid state NaBH_(4).The importance of carbon as catalyst support material for NaBH_(4) hydrolysis is also highlighted.
基金the National Natural Science Foundation of China(22078326,21878305,21908227)。
文摘In order to avoid the formation ofηphase(W_(6)Co_(6)C or W_(3)Co_(3)C)that adversely affects the sintering process and its products in the preparation process of ultra-fine WC-Co powder,a technical route of prereduction of WO_(3)-Co_(3)O_(4)to WO_(2)-Co and then deep reduction carbonization to WC-Co powder has been proposed.This study mainly investigates the influence of gas partial pressure on the pre-reduction process of WO_(3)-Co_(3)O_(4)under a mixed atmosphere of H_(2)-C_(2)H_(4)-Ar at 600℃and establishes the kinetic equations of pre-reduction and carbon evolution.The results indicate that increasing the partial pressure of hydrogen is conducive to the rapid and complete conversion of WO_(3) to WO_(2).High carbon content can be generated by the deposition of C_(2)H_(4),and it hinders the diffusion of the reducing gas;WO_(3)still cannot be completely reduced to WO_(2)as the partial pressure of C_(2)H_(4) increases to 60%.For the carbon evolution of C_(2)H_(4),the carbon amount is positively related to the H_(2)partial pressure,but it shows the highest amount and evolution rate when the ethylene partial pressure is 20%.Based on the reduction rate curves of WO_(3) and carbon evolution rate curves of C_(2)H_(4),the rate equations of pre-reduction and carbon evolution of WO_(3)-Co_(3)O_(4)system at 600℃are established.The pre-reduction reaction belongs to the first-order reaction,and its equation is expressed as follows:r=-(dw_(WO_(3)))/dt=(9±0.15)×10^(-2)×P_(H_(2))^(0.44)P_(C_(2)H_(4))&(0.57)The carbon deposition rate equation of C_(2)H_(4) can be expressed as follows:r=-(dc_C)/dt=r_f-r_b≌7.35×10^(-2)×P_(C_(2)H_(4))^(0.31)
基金supported by the National Natural Science Foundation of China(Grant No.22072022)the Natural Science Foundation of Fujian Province(2021L3003)the Science Foundation of Shandong Province(ZR2019BB065).
文摘Efficient photocatalytic reduction of CO_(2) to high-calorific-value CH4,an ideal target product,is a blueprint for C_(1)industry relevance and carbon neutrality,but it also faces great challenges.Herein,we demonstrate unprecedented hybrid SiC photocatalysts modified by Fe-based cocatalyst,which are prepared via a facile impregnation-reduction method,featuring an optimized local electronic structure.It exhibits a superior photocatalytic carbon-based products yield of 30.0μmol g^(−1) h^(−1) and achieves a record CH_(4) selectivity of up to 94.3%,which highlights the effectiveness of electron-rich Fe cocatalyst for boosting photocatalytic performance and selectivity.Specifically,the synergistic effects of directional migration of photogenerated electrons and strongπ-back bonding on low-valence Fe effectively strengthen the adsorption and activation of reactants and intermediates in the CO_(2)→CH_(4) pathway.This study inspires an effective strategy for enhancing the multielectron reduction capacity of semiconductor photocatalysts with low-cost Fe instead of noble metals as cocatalysts.
基金Natural Science Foundation of Xinjiang Province,Grant/Award Numbers:2019D01C064,2020D01A49,2020D01B25,2021D01B40National Natural Science Foundation of China,Grant/Award Numbers:21905209,52072273Tianshan innovation team project of Xinjiang Uygur Autonomous Region,Grant/Award Number:2021D14013。
文摘The persistent increase of CO_(2) levels in the atmosphere,already exceeding 400 ppm,urges the exploration of CO_(2) emission reduction and recycling technologies.Ideally,photocatalytic conversion of CO_(2) into valuable hydrocarbons realizes solar-to-chemical energy conversion,which is a desirable“kill two birds with one stone”strategy;namely,CO_(2) photoreduction can simultaneously tackle energy shortage and keep global carbon balance.Graphitic carbon nitride(g-C_(3)N_(4))working on CO_(2) reduction reaction deserves a highlight not only for the metal-free feature that endows it with low cost,tunable electronic structure,and easy fabrication properties but also because of its strong reduction ability.The present review concisely summarizes the latest advances of g-C_(3)N_(4)-based photocatalysts toward CO_(2) reduction.It starts with the discussion of thermodynamics and dynamics aspects of the CO_(2) reduction process.Then the modification strategies to promote g-C_(3)N_(4)-based photocatalysts in CO_(2) photoreduction have been discussed in detail,including surface functionalization,molecule structure engineering,crystallization,morphology engineering,loading cocatalyst,and constructing heterojunction.Meanwhile,the intrinsic factors affecting CO_(2) reduction activity and selectivity are analyzed and summarized.In the end,the challenges and prospects for the future development of highly g-C_(3)N_(4)-based photocatalysts in CO_(2) reduction are also presented.
基金supported by National Natural Science Foundation of China(Grant No.11804005,11375136,12204014)Anyang Institute of Technology Research Cultivation Fund(Grant No.YPY2019002)。
文摘Photocatalytic reduction of CO_(2) is considered as a kind of promising technologies for solving the greenhouse effect.Herein,a novel hybrid structure of g-C_(3)N_(4)/ZnO/Ti_(3)C_(2) photocatalysts was designed and fabricated to investigate their abilities for CO_(2) reduction.As demonstration,heterojunction of g-C_(3)N_(4)/ZnO can improve photogenerated carriers’separation,the addition of Ti_(3)C_(2) fragments can further facilitate the photocatalytic performance from CO_(2) to CO.Hence,g-C_(3)N_(4)/ZnO/Ti_(3)C_(2) has efficiently increased CO production by 8 and 12 times than pristine g-C_(3)N_(4) and ZnO,respectively.Which is ascribed to the photogenerated charge migration promoted by metallic Ti_(3)C_(2).This work provides a guideline for designing efficient hybrid catalysts on other applications in the renewable energy fields.
基金funded by the National Key Research and Development Program of China(2017YFA0700103,2018YFA0704502)the National Natural Science Foundation of China(21703248)staffs in BL11B beamline in Shanghai Synchrotron Radiation Facility(SSRF)for their technical assistance(2020-SSRF-PT-012223 and 2021-SSRF-PT-015319)。
文摘The conversion of CO_(2)into value-added chemicals coupled with the storage of intermittent renewable electricity is attractive.CuO nanosheets with an average size and thickness of~30 and~20 nm have been developed,which are in situ reduced into Cu nanosheets during electrochemical CO_(2)reduction reaction(ECO_(2)RR).The derived Cu nanosheets demonstrate much higher selectivity for C2H4production than commercial CuO derived Cu powder,with an optimum Faradaic efficiency of 56.2%and a partial current density of C_(2)H_(4)as large as 171.0 mA cm^(-2)in a gas diffusion flow cell.The operando attenuated total reflectance-Fourier transform infrared spectra measurements and density functional theory simulations illustrate that the high activity and selectivity of Cu nanosheets originate from the edge sites on Cu nanosheets with a coordinate number around 5(4–6),which facilitates the formation of^(*)CHO rather than^(*)COH intermediate,meanwhile boosting the C-C coupling reaction of^(*)CO and^(*)CHO intermediates,which are the critical steps for C_(2)H_(4)formation.
基金the National Natural Science Foundation of China(22208065)Guangxi Natural Science Foundation(2022GXNSFBA035483,2020GXNSFDA297007)+1 种基金Opening Project of Guangxi Key Laboratory of Petrochemical Resource Processing and Process Intensification Technology(2021K009,2020K002)Special funding for‘Guangxi Bagui Scholars’.
文摘Photocatalytic CO_(2)reduction to valuable product exhibit promising prospect for solving the energy crisis and the greenhouse effect.Herein,Co-Ti_(3)C_(2)T_(x)/g-C_(3)N_(4)(Co-TC/CN)composite with enhanced photocatalytic performance for converting CO_(2)to CO and CH_(4)was constructed by electrostatic self-assembly method.The close contact interface between Co-Ti_(3)C_(2)T_(x)and g-C_(3)N_(4)nanosheets can be used as fast transport channels of photogenerated electrons and effectively promote the separation of photogenerated electrons and holes,and the interface between the Co and Ti_(3)C_(2)T_(x)might be the active sites for CO_(2)adsorption and activation.The optimized Co-Ti_(3)C_(2)T_(x)/g-C_(3)N_(4)composite exhibited the highest photocatalytic performance with the CO and CH_(4)production of 55.04 μmol·g^(-1)and 2.29 μmol·g^(-1),respectively,which were 7.5 times and 5.8 times than those of g-C_(3)N_(4).Furthermore,the stability of g-C_(3)N_(4)was improved after coupling with Co-Ti_(3)C_(2)T_(x).
文摘?β-Unsaturated amides with various substitution pattems at the carbon-carbon double And and nitrogen atom can be reduced to the corresponding saturated amides with high selectivity and yields with NaBH4/BiCl3 system.
