质子交换膜电解水阳极析氧催化剂

Progress on the anode catalysts for proton exchange membrane water electrolysis

由可再生能源发电驱动的质子交换膜(proton exchange membrane, PEM)电解水被视为高效生产绿氢的理想策略.然而,酸性介质下兼具高活性与稳定性的PEM电解水析氧催化剂的开发仍是一个巨大挑战,阻碍了PEM电解水的推广应用.为此,本文综述了近年来酸性介质中析氧电催化剂的研究进展.首先通过对比酸性环境下不同反应路径的电催化析氧机理,从理论角度介绍了催化剂性能提升的策略.随后,分类介绍了近年来基于酸性电解质进行研究的各类析氧催化剂及其优化策略,发现通过充分利用催化活性点以及提升活性金属位点的本征催化活性等途径可增强析氧活性,并降低钌、铱基贵金属催化剂成本.为了解决贵金属催化剂的高成本问题,进一步减少甚至替代贵金属,讨论了对酸性环境耐受的非贵金属催化剂的开发,介绍了以Co、Mn和Sb基材料为代表的非贵金属催化剂进展.此外,对催化剂在酸性介质下阳极析氧反应的稳定性问题及优化策略进行总结,并正视了高电导率、高比表面积且稳定的阳极催化剂载体的关键作用.最后,总结并展望了酸性析氧催化剂优化路径,为未来研究高效低成本的PEM电解水阳极析氧催化剂提供参考.

The rapid development of the industry drives an intense demand for energy supply.Over the past century,fossil fuels such as coal,oil and natural gas have provided a strong energy support for the modernization of the world.However,the limited fossil fuels cannot satisfy the continuously increasing power requirement in the future any more.Meanwhile,severe environmental pollution caused by massive combustion of carbon-based fuels also brings great danger to human’s life.Therefore,it is urgent to develop renewable and clean energy to achieve sustainable development of the society.Renewable energy represented by hydropower,solar energy and wind power has attracted much attention and been widely utilized owing to its environmental friendliness and inexhaustible supply,while the uneven geographical distribution and fluctuation determine that it is unable to output electricity steadily and may lead to a waste of power.A key approach to this problem lies in converting the fluctuated renewable energy into stable chemical energy via electrochemical methods,and storing it as the chemical fuel.As a potential candidate,hydrogen works as an ideal carrier for power storage and supply due to its high energy density,free carbon emission and abundant reserve.Proton exchange membrane(PEM)water electrolysis driven by renewable energy is considered as a promising strategy for producing green hydrogen,by virtue of high operating current density,low ohmic loss,and flexible loading range.In comparison to the cathodic hydrogen production,the sluggish oxygen evolution reaction(OER)on the anode remains to be the bottleneck and retards the overall performance.Besides,the harsh acid environment on the membrane and high anode potential present severe challenges to the stability of the anode materials.Therefore,tremendous efforts have been devoted to developing active and durable anode catalysts for promoting the practical PEM-based OER proceeding under a strong acidic media during electrolysis.This review gives an overview on recent progress in the design and synthesis of robust electrocatalysts for acidic water oxidation,emphasizing the strategies for achieving high electrocatalytic activity without compromise in durability.Firstly,the mechanisms of electrocatalytic OER in acidic media,which include adsorbate evolution mechanism and lattice oxygen mediated mechanism,are discussed in detail to obtain the theoretical guideline on catalyst design.Subsequently,kinds of acidic OER catalysts are introduced and categorized to summarize the effective strategies for performance optimization.It was found that the OER performance can be enhanced by exposing more catalytic active sites as well as enhancing the intrinsic catalytic activity of the active sites.To reduce or even replace the noble metals and develop the cost-effective anode catalysts,the non-precious metal catalysts represented by Co,Mn and Sb-based materials,which are tolerant to acidic environments,are discussed.Then,the concerned stability of acidic OER and corresponding optimization methods are summarized.In addition,anode catalyst supports with high electrical conductivity,large specific surface area and good stability are squarely concluded,which also play a key role in water oxidation.At last,the various strategies to elevate OER performance are outlined,together with the perspectives of future-generation electrocatalysts for durable and cost-effective PEM water electrolysis.