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
探索低成本高效率的析氧电极对于工业电解水技术的发展至关重要.尽管镍铁水滑石已被公认为是一种高效析氧的非贵金属催化剂,但其本征活性还有待进一步提高.本研究通过将氧空位缺陷引入镍铁水滑石,设计出一种低成本高效率的析氧电极.通...探索低成本高效率的析氧电极对于工业电解水技术的发展至关重要.尽管镍铁水滑石已被公认为是一种高效析氧的非贵金属催化剂,但其本征活性还有待进一步提高.本研究通过将氧空位缺陷引入镍铁水滑石,设计出一种低成本高效率的析氧电极.通过精确电子结构调控,暴露更多活性位点,提高电极导电性,富缺陷镍铁水滑石电极展现出1.40 V(vs.RHE)的低起峰电位.同时,它仅需200 m V过电势就能达到10 m A cm^(-2)的电流密度,这相比未经处理的镍铁水滑石降低了48 m V.我们进一步通过密度泛函理论计算发现,氧空位缺陷的引入使Fe的价态降低,带隙减小,使得催化过程中电子更容易被激发到导带中,从而降低反应过电势并使析氧活性增强.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
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
文摘探索低成本高效率的析氧电极对于工业电解水技术的发展至关重要.尽管镍铁水滑石已被公认为是一种高效析氧的非贵金属催化剂,但其本征活性还有待进一步提高.本研究通过将氧空位缺陷引入镍铁水滑石,设计出一种低成本高效率的析氧电极.通过精确电子结构调控,暴露更多活性位点,提高电极导电性,富缺陷镍铁水滑石电极展现出1.40 V(vs.RHE)的低起峰电位.同时,它仅需200 m V过电势就能达到10 m A cm^(-2)的电流密度,这相比未经处理的镍铁水滑石降低了48 m V.我们进一步通过密度泛函理论计算发现,氧空位缺陷的引入使Fe的价态降低,带隙减小,使得催化过程中电子更容易被激发到导带中,从而降低反应过电势并使析氧活性增强.
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.
