La_(2)O_(3) catalyzed oxidative coupling of methane(OCM) is a promising process that converts methane directly to valuable C_(2)(ethylene and ethane) products. Our online MS transient study results indicate that prist...La_(2)O_(3) catalyzed oxidative coupling of methane(OCM) is a promising process that converts methane directly to valuable C_(2)(ethylene and ethane) products. Our online MS transient study results indicate that pristine surface without carbonate species demonstrates a higher selectivity to C_(2) products, and a lower light-off temperature as well. Further study is focused on carbonate-free La_(2)O_(3) catalyst surface for identification of active oxygen species associated with such products behavior. XPS reveals unique oxygen species with O 1 s binding energy of 531.5 e V correlated with OCM catalytic activity and carbonates removal. However, indicated thermal stability of this species is much higher than the surface peroxide or superoxide structures proposed by earlier computation models. Motivated by experimental results,DFT calculations reveal a new more stable peroxide structure, formed at the subsurface hexacoordinate lattice oxygen sites, with energy 2.18 e V lower than the previous models. The new model of subsurface peroxide provides a perspective for understanding of methyl radicals formation and C_(2) products selectivity in OCM over La_(2)O_(3) catalyst.展开更多
Electrochemically converting CO_(2)to value-added multi-carbon(C_(2+))fuels and chemicals is a favorable way to achieve carbon neutrality.Herein,polyaniline/CuO nanosheets(PANI/CuO NSs)hybrid electrocatalysts are deve...Electrochemically converting CO_(2)to value-added multi-carbon(C_(2+))fuels and chemicals is a favorable way to achieve carbon neutrality.Herein,polyaniline/CuO nanosheets(PANI/CuO NSs)hybrid electrocatalysts are developed in order to achieve superior C_(2+)selectivity by imparting PANI functional component to the CuO NSs.The decorated PANI nanoparticles(NPs)can effectively stabilize the*CO intermediates and increase their coverage on the active Cu sites,which facilitates the C-C coupling to form multi-carbon products.Benefiting from the synergetic effect of PANI and CuO NSs,best Faradaic efficiency(FE)for C_(2+)product up to 66.4%at-1.6 V vs.reversible hydrogen electrode(RHE)in a H-cell measurement and 60.0%at 400 mA·cm^(-2) in a flow cell measurement are demonstrated by PANI/CuO NSs-25 sample.More importantly,the C_(2+)selectivity keeps stable even in a continuous measurement time period of 92 h in H-cell measurement.The present study may provide more insights for designing efficient hybrid materials toward superior C_(2+)production from electrocatalytic CO_(2)reduction.展开更多
基金the Key Projects of Shanghai Science and Technology Commission (18JC1412100)the National Natural Science Foundation of China (No. 91745105, 22072092, 92045301)+2 种基金the startup funding provided by Shanghai Tech University for funding their participation in this workfunding provided through The Shell Foundation Grants (No. PT66201)the support from Analytical Instrumentation Center (contract no. SPSTAIC10112914), SPST, Shanghai Tech University。
文摘La_(2)O_(3) catalyzed oxidative coupling of methane(OCM) is a promising process that converts methane directly to valuable C_(2)(ethylene and ethane) products. Our online MS transient study results indicate that pristine surface without carbonate species demonstrates a higher selectivity to C_(2) products, and a lower light-off temperature as well. Further study is focused on carbonate-free La_(2)O_(3) catalyst surface for identification of active oxygen species associated with such products behavior. XPS reveals unique oxygen species with O 1 s binding energy of 531.5 e V correlated with OCM catalytic activity and carbonates removal. However, indicated thermal stability of this species is much higher than the surface peroxide or superoxide structures proposed by earlier computation models. Motivated by experimental results,DFT calculations reveal a new more stable peroxide structure, formed at the subsurface hexacoordinate lattice oxygen sites, with energy 2.18 e V lower than the previous models. The new model of subsurface peroxide provides a perspective for understanding of methyl radicals formation and C_(2) products selectivity in OCM over La_(2)O_(3) catalyst.
文摘Electrochemically converting CO_(2)to value-added multi-carbon(C_(2+))fuels and chemicals is a favorable way to achieve carbon neutrality.Herein,polyaniline/CuO nanosheets(PANI/CuO NSs)hybrid electrocatalysts are developed in order to achieve superior C_(2+)selectivity by imparting PANI functional component to the CuO NSs.The decorated PANI nanoparticles(NPs)can effectively stabilize the*CO intermediates and increase their coverage on the active Cu sites,which facilitates the C-C coupling to form multi-carbon products.Benefiting from the synergetic effect of PANI and CuO NSs,best Faradaic efficiency(FE)for C_(2+)product up to 66.4%at-1.6 V vs.reversible hydrogen electrode(RHE)in a H-cell measurement and 60.0%at 400 mA·cm^(-2) in a flow cell measurement are demonstrated by PANI/CuO NSs-25 sample.More importantly,the C_(2+)selectivity keeps stable even in a continuous measurement time period of 92 h in H-cell measurement.The present study may provide more insights for designing efficient hybrid materials toward superior C_(2+)production from electrocatalytic CO_(2)reduction.
