自组装百合花状超低Ru,Ni掺杂的Fe_(2)O_(3)用于大电流碱性海水电解双功能电催化

Controllable synthesis of a self-assembled ultralow Ru,Ni-doped Fe_(2)O_(3) lily as a bifunctional electrocatalyst for large-current-density alkaline seawater electrolysis

随着环境问题的加剧和化石燃料的逐渐枯竭,探索可再生能源势在必行.由于氢气具有无污染和高能量密度的特点,被视为一种很有前途的、可以用以替代传统燃料的可再生能源.电催化分解水的方法可以在不产生有害污染物的前提下,生产高纯度的氢气,因此被认为是最理想的清洁制氢技术.海水储量丰富,如果将海水作为天然电解质代替纯水应用于大规模生产氢气,可同时实现海水淡化和产氢的双重目的.与纯水分解一样,海水裂解也由两个半反应组成,包括阳极析氧反应(OER)和阴极析氢反应(HER).然而,与纯水相比,海水因存在导电率低和离子腐蚀等问题,制氢更具有挑战性.众所周知,海水中丰富的氯离子(~0.5 mol/L)可能会在阳极侧引起析氯反应(ClER),该反应会与OER发生竞争,因此,用于海水电解过程的电极材料活性位点可能被毒化.一般来说,ClER的起始电位仅比OER高约490 mV,为了避免ClER的发生,需要活性高且稳定性好的OER催化剂在低于490 mV的过电位下实现更大的电流密度.因此,利用简便可控的合成方法制备高效稳定的双功能电催化剂用于大电流碱性海水电解仍然面临巨大挑战.本文通过简单的一步水热工艺,在泡沫铁(RuNi-Fe_(2)O_(3)/IF)上可控合成了具有百合形态的自组装超低Ru,Ni掺杂的Fe_(2)O_(3),其中完整的百合形RuNi-Fe_(2)O_(3)/IF是通过调整Ru/Ni比获得的.得益于Ru/Ni的化学取代,所合成的RuNi-Fe_(2)O_(3)/IF可作为独立双功能电极,用于电催化HER和OER反应.对于HER(OER)来说,在1.0 mol/L KOH电解液中,需要75.0 mV(329.0 mV)的过电位便可驱动100 mA cm_(-2)的电流密度.此外,整体水分裂仅需1.66和1.73 V的超低电压,即可在1.0 mol/L KOH和1.0 mol/L KOH海水电解质中驱动100 mA cm^(-2)的电流,甚至超过了由贵金属催化剂组成的双电极体系,并且在100 mA cm^(-2)左右可保持100 h以上,表现出较好的耐久性.综上,本文为合成用于大电流碱性海水电解的独立式双功能电极提供了一种高效、经济的合成方法,对环境保护和能源开发具有重要意义.

Highly efficient and stable bifunctional electrocatalysts that can be used for large-current-density electrolysis of alkaline seawater are highly desirable for carbon-neutral economies,but their facile and controllable synthesis remains a challenge.Here,self-assembled ultralow Ru,Ni-doped Fe_(2)O_(3) with a lily shaped morphology was synthesized on iron foam(RuNi-Fe_(2)O_(3)/IF)via a facile one-step hydrothermal process,in which the intact lily shaped RuNi-Fe_(2)O_(3)/IF was obtained by adjusting the ratio of Ru/Ni.Benefitting from the Ru/Ni chemical substitution,the as-synthesized RuNi-Fe_(2)O_(3)/IF can act as free-standing dual-function electrodes that are applied to electrocatalysis for the hydrogen evolution(HER)and oxygen evolution reactions(OER)in 1.0 mol L^(-1) KOH,requiring an overpotential of 75.0 mV to drive 100 mA cm^(-2) for HER and 329.0 mV for OER.Moreover,the overall water splitting catalyzed by RuNi-Fe_(2)O_(3)/IF only demands ultralow cell voltages of 1.66 and 1.73 V to drive 100 mA cm^(-2) in 1.0 mol L^(-1) KOH and 1.0 mol L^(-1) KOH seawater electrolytes,respectively.The electrodes show remarkable long-term durability,maintaining current densities exceeding 100 mA cm^(-2) for more than 100 h and thus outperforming the two-electrode system composed of noble catalysts.This work provides an efficient,economical method to synthesize self-standing bifunctional electrodes for large-current-density alkaline seawater electrolysis,which is of significant importance for ecological protection and energy exploitation.