铋掺杂的二氧化钌催化剂用于高效酸性水氧化

A Bi-doped RuO_(2)catalyst for efficient and durable acidic water oxidation

目前,电解水是一种很有前景的制氢方式,它能够将可持续能源产生的电能转化为储存在氢键中的化学能,实现高效的能源转换.与传统碱性电解槽相比,质子交换膜水电解槽(PEMWE)由于工作温度低、电压效率高、电流密度高和兼容性好,是一种很有发展潜力的绿色制氢技术.然而,PEMWE阳极析氧反应(OER)缓慢的反应动力学通常需要消耗更多能量,极大降低工作效率并限制了其发展.目前氧化铱(IrO_(2))仍然是唯一能商业应用的PEMFC阳极催化剂.但铱储量少且成本高严重阻碍了PEMFC大规模应用.近年来,氧化钌(RuO_(2))因其高固有活性且价格相对低廉被认为是IrO_(2)在酸性OER中潜在的替代品.然而,RuO_(2)在酸性OER中稳定性较差,长时间会发生晶体结构崩塌和溶解.因此,开发出一种有效的策略来平衡RuO_(2)基催化剂的稳定性和活性之间的关系对PEMWE的实际应用至关重要.本文采用铋(Bi)掺杂来调控RuO_(2)的酸性OER电催化剂(Bi_(0.15)Ru_(0.85)O_(2)),同时提高了其酸性OER的活性和稳定性.在0.5molL^(-1)H_(2)SO_(4)溶液中,Bi_(0.15)Ru_(0.85)O_(2)在10 mAcm^(-2)下酸性OER的过电位为200.0 mV,远低于RuO_(2)和商业RuO_(2),且具有长达100 h的稳定性.X射线光电子能谱(XPS)和Ru L_(2,3)边X射线吸收近边结构(XANES)结果表明,引入Bi元素后,Bi_(0.15)Ru_(0.85)O_(2)中Ru的初始氧化态升高,有利于OER过程中Ru活性中心的氧化,激活活性位点,从而提高催化活性.电化学实验、紫外光发射光谱和紫外可见光谱等结果表明,Bi_(0.15)Ru_(0.85)O_(2)比RuO_(2)具有更快的电子转移能力和更好的导电性,从而提升了催化过程的反应动力学.Bi和Ru之间的强电子相互作用也有利于提高催化剂结构的稳定性以及在OER过程中的稳定性.此外,本文还通过原位拉曼光谱研究了Bi_(0.15)Ru_(0.85)O_(2)和RuO_(2)的催化机理,更加深入地了解其构效关系.表观活化能测试和密度泛函理论结果表明,Bi的引入可以有效降低速率决定步骤的表观活化能和能垒,从而大大提升催化性能.综上所述,本文成功制备了高性能的RuO_(2)基电催化剂,并将其应用于酸性OER中.Bi_(0.15)Ru_(0.85)O_(2)中Ru活性位点的激活以及强电子相互作用有利于平衡活性和稳定性之间的关系,实现同时提高催化活性和稳定性,对酸性OER催化剂的设计提供了新思路.

Ruthenium oxide-based electrocatalysts have been regarded as promising alternatives to the state-of-the-art Iridium oxide(IrO_2)towards acidic oxygen evolution reaction(OER).However,their practical applications of proton exchange membrane water electrolyzer(PEMWE)are severely limited by the lack of efficient strategy to balance the seesaw relation between stability and activity of ruthenium oxide(RuO_2)-based catalysts.Herein,we report that both the activity and stability of RuO_(2)can be significantly boosted though bismuth(Bi)doping.We find that the introduction of Bi can increase the initial valance state of Ru in Bi_(0.15)Ru_(0.85)O_2,which can promote the activation of Ru active sites,and facilitate the reaction kinetics of acidic OER.Besides,the presence of Bi can strengthen the electron interaction to maintain the structure stability and improve the electrocatalytic performance by reducing the energy barriers and avoiding the overoxidation of active species.The obtained Bi_(0.15)Ru_(0.85)O_(2)catalyst shows a low overpotential of 200.0 m V to reach a current density of 10 m A cm~(-2)under acidic media,and a long-term stability for over 100 hours.Our work provides an important inspiration to rational design RuO_2-based electrocatalysts with high activity and durability toward acidic OER.