Development of active and non-noble metal-based catalyst for H2 production via NH3 decomposition is crucial for the implementation of NH3 as a H2 carrier.Co-based catalysts have received increasing attention because o...Development of active and non-noble metal-based catalyst for H2 production via NH3 decomposition is crucial for the implementation of NH3 as a H2 carrier.Co-based catalysts have received increasing attention because of its high intrinsic activity and moderate cost.In this work,we examined the effect of BaNH,CaNH and Mg3 N2 on the catalytic activity of Co in the NH3 decomposition reaction.The H2 formation rate ranks the order as Co-BaNH>Co-CaNH>Co-Mg3 N2≈Co/CNTs within a reaction temperature range of 300-550℃.It is worth pointing out that the H2 formation rate of Co-BaNH at 500℃reaches20 mmolH2 gcat-1 min-1,which is comparable to those of the active Ru/Al2 O3(ca.17 mmolH2 gcat-1 min1)and Ru/AC(21 mmolH2 gcat-1 min-1)catalysts under the similar reaction conditions.In-depth research shows that Co-BaNH exhibits an obviously higher intrinsic activity and much lower Ea(46.2 kJ mol-1)than other Co-based catalysts,suggesting that BaNH may play a different role from CaNH,Mg3 N2 and CNTs during the catalytic process.Combined results of XRD,Ar-TPD and XAS show that a[Co-N-Ba]-like intermediate species is likely formed at the interface of Co metal and BaNH,which may lead to a more energy-efficient reaction pathway than that of neat Co metal for NH3 decomposition.展开更多
Density functional theory was used to study the NH3 behavior on Ni monolayer covered Pt（111） and WC（001）. The electronic structure of the surfaces, and the adsorption and decomposition of NH3 were calculated and c...Density functional theory was used to study the NH3 behavior on Ni monolayer covered Pt（111） and WC（001）. The electronic structure of the surfaces, and the adsorption and decomposition of NH3 were calculated and compared. Ni atoms in the monolayer behave different from that in Ni（111）. More dz2 electrons of Ni in monolayer covered systems were shifted to other regions compared to Ni（111）, charge density depletion on this orbital is crucial to NH3 adsorption. NH3 binds more stable on Ni/Pt（lll） and Ni/WC（001） than on Ni（111）, the energy barriers of the first N-H bond scission were evidently lower on Ni/Pt（111） and Ni/WC（001） than on Ni（111）, these are significant to NH3 decomposition. N recombination is the rate-limiting step, high reaction barrier implies that N2 is produced only at high temperatures. Although WC has similar properties to Pt, differences of the electronic structure and catalytic activities are observed for Ni/Pt（111） and Ni/WC （001）, the energy barrier for the rate-determined step increases on Ni/WC（001） instead of decreasing on Ni/Pt（lll） when compared to Ni（111）. the N recombination barrier by modifying To design cheaper and better catalysts, reducing Ni/WC（001） is a critical question to be solved.展开更多
基金financial supports from the Project of the National Natural Science Foundation of China(Grant Nos.21633011and 21872137)“Transformational Technologies for Clean Energy and Demonstration”+2 种基金Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA21000000)Youth Innovation Promotion Association CAS(No.2018213)the Shanghai Synchrotron Radiation Facility(SSRF)for providing the beam time。
文摘Development of active and non-noble metal-based catalyst for H2 production via NH3 decomposition is crucial for the implementation of NH3 as a H2 carrier.Co-based catalysts have received increasing attention because of its high intrinsic activity and moderate cost.In this work,we examined the effect of BaNH,CaNH and Mg3 N2 on the catalytic activity of Co in the NH3 decomposition reaction.The H2 formation rate ranks the order as Co-BaNH>Co-CaNH>Co-Mg3 N2≈Co/CNTs within a reaction temperature range of 300-550℃.It is worth pointing out that the H2 formation rate of Co-BaNH at 500℃reaches20 mmolH2 gcat-1 min-1,which is comparable to those of the active Ru/Al2 O3(ca.17 mmolH2 gcat-1 min1)and Ru/AC(21 mmolH2 gcat-1 min-1)catalysts under the similar reaction conditions.In-depth research shows that Co-BaNH exhibits an obviously higher intrinsic activity and much lower Ea(46.2 kJ mol-1)than other Co-based catalysts,suggesting that BaNH may play a different role from CaNH,Mg3 N2 and CNTs during the catalytic process.Combined results of XRD,Ar-TPD and XAS show that a[Co-N-Ba]-like intermediate species is likely formed at the interface of Co metal and BaNH,which may lead to a more energy-efficient reaction pathway than that of neat Co metal for NH3 decomposition.
文摘Density functional theory was used to study the NH3 behavior on Ni monolayer covered Pt（111） and WC（001）. The electronic structure of the surfaces, and the adsorption and decomposition of NH3 were calculated and compared. Ni atoms in the monolayer behave different from that in Ni（111）. More dz2 electrons of Ni in monolayer covered systems were shifted to other regions compared to Ni（111）, charge density depletion on this orbital is crucial to NH3 adsorption. NH3 binds more stable on Ni/Pt（lll） and Ni/WC（001） than on Ni（111）, the energy barriers of the first N-H bond scission were evidently lower on Ni/Pt（111） and Ni/WC（001） than on Ni（111）, these are significant to NH3 decomposition. N recombination is the rate-limiting step, high reaction barrier implies that N2 is produced only at high temperatures. Although WC has similar properties to Pt, differences of the electronic structure and catalytic activities are observed for Ni/Pt（111） and Ni/WC （001）, the energy barrier for the rate-determined step increases on Ni/WC（001） instead of decreasing on Ni/Pt（lll） when compared to Ni（111）. the N recombination barrier by modifying To design cheaper and better catalysts, reducing Ni/WC（001） is a critical question to be solved.
