Nickel-iron layered double hydroxide （NiFe-LDH） nanosheets have shown optimal oxygen evolution reaction （OER） performance; however, the role of the intercalated ions in the OER activity remains unclear. In this wo...Nickel-iron layered double hydroxide （NiFe-LDH） nanosheets have shown optimal oxygen evolution reaction （OER） performance; however, the role of the intercalated ions in the OER activity remains unclear. In this work, we show that the activity of the NiFe-LDHs can be tailored by the intercalated anions with different redox potentials. The intercalation of anions with low redox potential （high reducing ability）, such as hypophosphites, leads to NiFe-LDHs with low OER overpotential of 240 mV and a small Tafel slope of 36.9 mV/dec, whereas NiFe-LDHs intercalated with anions of high redox potential （low reducing ability）, such as fluorion, show a high overpotential of 370 mV and a Tafel slope of 80.8 mV/dec. The OER activity shows a surprising linear correlation with the standard redox potential. Density functional theory calculations and X-ray photoelectron spectroscopy analysis indicate that the intercalated anions alter the electronic structure of metal atoms which exposed at the surface. Anions with low standard redox potential and strong reducing ability transfer more electrons to the hydroxide layers. This increases the electron density of the surface metal sites and stabilizes their high-valence states, whose formation is known as the critical step prior to the OER process.展开更多
Photocatalytic reduction of CO2(CO2PR)to valuable solar fuels is considered as a promising route to the amelioration of fossil fuel conundrum and the mitigation of greenhouse gases.Although progress has been made to e...Photocatalytic reduction of CO2(CO2PR)to valuable solar fuels is considered as a promising route to the amelioration of fossil fuel conundrum and the mitigation of greenhouse gases.Although progress has been made to enhance CO2PR performance,the available method that can promote the selectivity of CO2PR products remains to be a challenge.In this work,we synthesized NO3-or CO32-intercalated NiAl-layered double hydroxide(NiAl-LDH)photocatalysts and investigated the performance of CO2PR in the presence of an electron donor and a photosensitizer.Compared with Ni2Al-CO32-,Ni2Al-NO3-exhibited superior catalytic performance in the CO2PR,and the resulted selectivity of CH4 in Ni2Al-NO3-(6.1%)was 12.2 times that of Ni2Al-CO32-(0.5%)under visible light irradiation.X-Ray absorption fine structure(XAFS)result reveals a relative abundance of defects in Ni2Al-NO3-,which played as active sites and promoted charge transfer in CO2PR for the efficient CH4 evolution.展开更多
基金This work was supported by the National Natural Science Foundation of China （NSFC）, the National Key Research and Development Project （Nos. 2016YFF0204402 and 2016YFC0801302）, the Program for Changjiang Scholars, and innovative Research Team in the University, and the Fundamental Research Funds for the Central Universities, and the long term subsidy mechanism from the Ministry of Finance and the Ministry of Education of China. S. S. gratefully acknowledges Villum Foundation.
文摘Nickel-iron layered double hydroxide （NiFe-LDH） nanosheets have shown optimal oxygen evolution reaction （OER） performance; however, the role of the intercalated ions in the OER activity remains unclear. In this work, we show that the activity of the NiFe-LDHs can be tailored by the intercalated anions with different redox potentials. The intercalation of anions with low redox potential （high reducing ability）, such as hypophosphites, leads to NiFe-LDHs with low OER overpotential of 240 mV and a small Tafel slope of 36.9 mV/dec, whereas NiFe-LDHs intercalated with anions of high redox potential （low reducing ability）, such as fluorion, show a high overpotential of 370 mV and a Tafel slope of 80.8 mV/dec. The OER activity shows a surprising linear correlation with the standard redox potential. Density functional theory calculations and X-ray photoelectron spectroscopy analysis indicate that the intercalated anions alter the electronic structure of metal atoms which exposed at the surface. Anions with low standard redox potential and strong reducing ability transfer more electrons to the hydroxide layers. This increases the electron density of the surface metal sites and stabilizes their high-valence states, whose formation is known as the critical step prior to the OER process.
基金Supported by the National Natural Science Foundation of China(Nos.U1707603,21625101,21521005,U1507102 and 21878008)the National Key Research and Development Program of China(No.2017YFB0307303)+2 种基金the National Basic Research Program(973 Program)of China(No.2014CB932104)the Natural Science Foundation of Beijing,China(Nos.2182047,2202036)the Fundamental Research Funds for the Central Universities,China(No.XK1802-6).
文摘Photocatalytic reduction of CO2(CO2PR)to valuable solar fuels is considered as a promising route to the amelioration of fossil fuel conundrum and the mitigation of greenhouse gases.Although progress has been made to enhance CO2PR performance,the available method that can promote the selectivity of CO2PR products remains to be a challenge.In this work,we synthesized NO3-or CO32-intercalated NiAl-layered double hydroxide(NiAl-LDH)photocatalysts and investigated the performance of CO2PR in the presence of an electron donor and a photosensitizer.Compared with Ni2Al-CO32-,Ni2Al-NO3-exhibited superior catalytic performance in the CO2PR,and the resulted selectivity of CH4 in Ni2Al-NO3-(6.1%)was 12.2 times that of Ni2Al-CO32-(0.5%)under visible light irradiation.X-Ray absorption fine structure(XAFS)result reveals a relative abundance of defects in Ni2Al-NO3-,which played as active sites and promoted charge transfer in CO2PR for the efficient CH4 evolution.
