In situ growth of minimal Ir-incorporated CoxNi1-xO nanowire arrays on Ni foam with improved electrocatalytic activity for overall water splitting

微量铱掺杂CoxNi1-xO纳米线阵列的制备及其电催化性能（英文）

Exploration of cost-effective electrocatalysts for boosting the overall water-splitting efficiency is vitally important for obtaining renewable fuels such as hydrogen.Here,earth-abundant CoxNi1-xO nanowire arrays were used as a structural framework to dilute Ir incorporation for fabricating electrocatalysts for water splitting.Minimal Ir-incorporated CoxNi1-xO nanowire arrays were synthesized through the facile hydrothermal method with subsequent calcination by using Ni foam(NF)as both the substrate and source of Ni.The electrocatalytic water-splitting performance was found to crucially depend on the Ir content of the parent CoxNi1-xO nanowire arrays.As a result,for a minimal Ir content,as low as 0.57 wt%,the obtained Ir-CoxNi1-xO/NF electrodes exhibited optimal catalytic activity in terms of a low overpotential of 260 mV for the oxygen evolution reaction and 53 mV for the hydrogen evolution reaction at 10 mA cm?2 in 1 mol L–1 KOH.When used as bifunctional electrodes in water splitting,the current density of 10 mA cm–2 was obtained at a low cell voltage of 1.55 V.Density functional theory calculations revealed that the Ir-doped CoxNi1-xO arrays exhibited enhanced electrical conductivity and low Gibbs free energy,which contributed to the improved electrocatalytic activity.The present study presents a new strategy for the development of transition metal oxide electrocatalysts with low levels of Ir incorporation for efficient water splitting.

电催化剂可以降低水分解反应的活化能与相应的过电势,提高电解水的制氢效率.Pt、Ru等贵金属颗粒是最常见的高催化活性材料,但其高昂成本严重限制了它们在工业上的广泛应用.因此,开发以非贵金属为基础的高活性材料是未来实现大规模工业制氢的有效手段.本文以CoxNi1-xO纳米线阵列为结构骨架对其进行微量的铱(Ir)掺杂,同时将Ir的掺杂量控制在1%以下,并系统地研究了Ir-CoxNi1-xO材料的析氢反应(HER)、析氢反应(OER)和全解水性能.实验发现,微量Ir掺杂可以有效提升CoxNi1-xO纳米材料的电化学性能.当Ir在样品的含量仅为0.57 wt%时,Ir掺杂的CoxNi1-xO样品具有最优异的HER和OER性能.特别地,在1 mol L^–1 KOH电解液中电流密度达到10 mA cm^–2时的HER过电势仅为260 mV,OER过电势仅为53 mV.将Ir(0.57 wt%)-CoxNi1-xO/NF样品作为双功能催化剂用于全解水的阳极和阴极时产生10mA cm^–2电流密度需要施加的电压仅为1.55 V.采用第一性原理(DFT)对Ir元素掺杂在调控CoxNi1-xO的电子结构和HER以及OER反应中被吸附物吉布斯自由能的改变等方面进行了量化计算.结果表明,Ir掺杂后CoxNi1-xO总的态密度向导带移动,带隙内电子的相互作用增强,相应的禁带宽度变小,表现为半金属的导电类型,说明Ir掺杂提高了CoxNi1-xO材料的导电性.相应的吉布斯自由能计算结果表明,Ir掺杂后材料表面对氢原子吸附的活性加强,ΔGH*由原来的0.823 eV变为0.523 eV,更加接近理想催化剂的值.同样地,计算表明CoxNi1-xO在参与OER反应时对中间体吸附的吉布斯自由能在Ir掺杂后也得到降低.