Electrocatalytic CO_(2) conversion has been considered as a promising way to recycle CO_(2) and produce sustainable fuels and chemicals.However,the efficient and highly selective electrochemical reduction of CO_(2) di...Electrocatalytic CO_(2) conversion has been considered as a promising way to recycle CO_(2) and produce sustainable fuels and chemicals.However,the efficient and highly selective electrochemical reduction of CO_(2) directly into multi‐carbon(C_(2+))products remains a great challenge.Herein,we synthesized three type catalysts with different morphologies based on Cu_(2)O nanowires,and studied their morphology and crystal facet reconstruction during the pre‐reduction process.Benefiting from abundant exposure of Cu(100)crystal facet,the nanosheet structure derived Cu catalyst showed a high faradaic efficiency(FE)of 67.5%for C_(2+)products.Additionally,electrocatalytic CO_(2) reduction studies were carried out on Cu(100),Cu(110),and Cu(111)single crystal electrodes,which verified that Cu(100)crystal facets are favorable for the C_(2+)products in electrocatalytic CO_(2) reduction.Our work showed that catalysts would reconstruct during the CO_(2) reduction process and the importance in morphology and crystal facet control to obtain desired products.展开更多
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
Oxygen evolution reaction is critical for water splitting or metal-air batteries,but previous research mainly focuses on electrode material or structure optimization.Herein,we demonstrate that surfactant modification ...Oxygen evolution reaction is critical for water splitting or metal-air batteries,but previous research mainly focuses on electrode material or structure optimization.Herein,we demonstrate that surfactant modification of a NiFe layered double hydroxide (LDH) array electrode,one of the best catalysts for oxygen evolution reaction (OER),could achieve superaerophobic surface with balanced surface charges,affording fast mass transfer,quick gas release,and boosted OER performance.The assembled surfactants on the electrode surface are responsible for lowering the bubble adhesive force (~ 1.03 μN) and corresponding fast release of small bubbles generated during OER.In addition,the bipolar nature of the hexadecyl trimethyl ammonium bromide (CTAB) molecule lead to bilayer assembly of the surfactants with the polar ends facing the electrode surface and the electrolyte,resulting in neutralized charges on the electrode surface.As a result,OH-transfer was facilitated and OER performance was enhanced.With the modified superaerophobic surface and balanced surface charge,NiFe LDHs-CTAB nanostructured electrode showed ultrahigh current density increase (9.39 mA(mV·cm^2)),2.3 times higher than that for conventional NiFe LDH nanoarray electrode),dramatically fast gas release,and excellent durability.The introduction of surfactants to construct under-water superaerophobic electrode with in-time repelling ability to the as-formed gas bubbles may open up a new pathway for designing efficient electrodes for gas evolution systems with potentially practical application in the near future.展开更多
Exploring efficient and cost-effective electro- catalysts for oxygen evolution reaction （OER） is critical to water splitting. While nickel-iron layered double hydroxide （NiFe LDH） has been long recognized as a pro...Exploring efficient and cost-effective electro- catalysts for oxygen evolution reaction （OER） is critical to water splitting. While nickel-iron layered double hydroxide （NiFe LDH） has been long recognized as a promising non- precious electrocatalyst for OER, its intrinsic activity needs further improvement. Herein, we design a highly-efficient oxygen evolution electrode based on defective NiFe LDH na- noarray. By combing the merits of the modulated electronic structure, more exposed active sites, and the conductive elec- trode, the defective NiFe LDH electrocatalysts show a low onset potential of 1.40 V （vs. RHE）. An overpotential of only 200 mV is required for 10 mA cm-2, which is 48 mV lower than that of pristine NiFe-LDH. Density functional theory plus U （DFT＋U） calculations are further employed for the origin of this OER activity enhancement. We find the introduction of oxygen vacancies leads to a lower valance state of Fe and the narrowed bandgap, which means the electrons tend to be ea- sily excited into the conduction band, resulting in the lowered reaction overpotential and enhanced OER performance.展开更多
文摘Electrocatalytic CO_(2) conversion has been considered as a promising way to recycle CO_(2) and produce sustainable fuels and chemicals.However,the efficient and highly selective electrochemical reduction of CO_(2) directly into multi‐carbon(C_(2+))products remains a great challenge.Herein,we synthesized three type catalysts with different morphologies based on Cu_(2)O nanowires,and studied their morphology and crystal facet reconstruction during the pre‐reduction process.Benefiting from abundant exposure of Cu(100)crystal facet,the nanosheet structure derived Cu catalyst showed a high faradaic efficiency(FE)of 67.5%for C_(2+)products.Additionally,electrocatalytic CO_(2) reduction studies were carried out on Cu(100),Cu(110),and Cu(111)single crystal electrodes,which verified that Cu(100)crystal facets are favorable for the C_(2+)products in electrocatalytic CO_(2) reduction.Our work showed that catalysts would reconstruct during the CO_(2) reduction process and the importance in morphology and crystal facet control to obtain desired products.
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This work was financially supported by the National Natural Science Foundation of China,the Program for Changjiang Scholars and Innovative Research Team in the University,the Fundamental Research Funds for the Central Universities,the Long-Term Subsidy Mechanism from the Ministry of Finance and the Ministry of Education of China,the National Key Research and Development Program of China(Nos.2016YFF0204402 and 2018YFB1502401).
文摘Oxygen evolution reaction is critical for water splitting or metal-air batteries,but previous research mainly focuses on electrode material or structure optimization.Herein,we demonstrate that surfactant modification of a NiFe layered double hydroxide (LDH) array electrode,one of the best catalysts for oxygen evolution reaction (OER),could achieve superaerophobic surface with balanced surface charges,affording fast mass transfer,quick gas release,and boosted OER performance.The assembled surfactants on the electrode surface are responsible for lowering the bubble adhesive force (~ 1.03 μN) and corresponding fast release of small bubbles generated during OER.In addition,the bipolar nature of the hexadecyl trimethyl ammonium bromide (CTAB) molecule lead to bilayer assembly of the surfactants with the polar ends facing the electrode surface and the electrolyte,resulting in neutralized charges on the electrode surface.As a result,OH-transfer was facilitated and OER performance was enhanced.With the modified superaerophobic surface and balanced surface charge,NiFe LDHs-CTAB nanostructured electrode showed ultrahigh current density increase (9.39 mA(mV·cm^2)),2.3 times higher than that for conventional NiFe LDH nanoarray electrode),dramatically fast gas release,and excellent durability.The introduction of surfactants to construct under-water superaerophobic electrode with in-time repelling ability to the as-formed gas bubbles may open up a new pathway for designing efficient electrodes for gas evolution systems with potentially practical application in the near future.
基金supported by the National Natural Science Foundation of China,National Key Research and Development Project (2016YFC0801302, 2016YFF0204402)the Program for Changjiang Scholars and Innovative Research Team in the University+2 种基金the Fundamental Research Funds for the Central Universitiesthe longterm subsidy mechanism from the Ministry of Financethe Ministry of Education of China
文摘Exploring efficient and cost-effective electro- catalysts for oxygen evolution reaction （OER） is critical to water splitting. While nickel-iron layered double hydroxide （NiFe LDH） has been long recognized as a promising non- precious electrocatalyst for OER, its intrinsic activity needs further improvement. Herein, we design a highly-efficient oxygen evolution electrode based on defective NiFe LDH na- noarray. By combing the merits of the modulated electronic structure, more exposed active sites, and the conductive elec- trode, the defective NiFe LDH electrocatalysts show a low onset potential of 1.40 V （vs. RHE）. An overpotential of only 200 mV is required for 10 mA cm-2, which is 48 mV lower than that of pristine NiFe-LDH. Density functional theory plus U （DFT＋U） calculations are further employed for the origin of this OER activity enhancement. We find the introduction of oxygen vacancies leads to a lower valance state of Fe and the narrowed bandgap, which means the electrons tend to be ea- sily excited into the conduction band, resulting in the lowered reaction overpotential and enhanced OER performance.
