Mo掺杂La0.8Sr0.2Co1-xMoxO3-δ的电催化析氧、析氢性能研究

Study on the Electrocatalytic Oxygen and Hydrogen Evolution Performance of Mo-Doped La0.8Sr0.2Co1-xMoxO3-δ

摘要:

电解水制氢是一种清洁、高效和安全的技术，极具发展潜力的制氢手段。电解水制氢过程中，阳极析氧（OER）和阴极析氢（HER）动力学缓慢，需要较高的过电位突破能量壁垒，导致耗能较高。高效OER和HER催化剂的使用是提高电解水效率的关键，开发高活性、高稳定性和低成本的OER和HER双功能电催化剂，可极大促进电解水制氢的产 业化发展。钙钛矿氧化物（结构式ABO₃）电催化剂具有储量丰富、结构与成分易调控等优点，在电催化水分解制氢催化剂的研究中广受关注。钙钛矿氧化物的B位离子掺杂是增强其电催化活性的常见策略，合理选择B位掺杂元素的种 类和含量，不仅可调控钙钛矿氧化物的晶体结构、获得更高的催化活性，还可赋予其双功能催化性能。以La_0.8Sr_0.2CoO_3-δ钙钛矿氧化物为原料，通过高价Mo离子掺杂，采用固相合成法制备了La_0.8Sr_0.2Co_1-xMo_xO_3-δ（LSCM，x=0、0.05、0.1、0.2）系列钙钛矿材料，研究了Mo掺杂量（质量分数）对钙钛矿材料电催化析氧和析氢性能的影响。结果表明，掺杂少量Mo元素，不会改变LSCM的物相和微观形貌，但可有效提升OER和HER的催化活性，其主要原因是Mo掺杂改变了Co的价态、氧空位和晶体结构对称性。适量Mo元素掺杂对LSC钙钛矿氧化物的析氢和析氧性能均有提高，但随着Mo掺杂量增多，LSCM的OER和HER催化活性均开始下降。当Mo质量分数为5%时，La_0.8Sr_0.2Co_0.95Mo_0.05O_3-δ（LSCM-5）具有最优异的OER和HER催化活性，在10 mA?cm^-2电流密度下，OER和HER过电位分别为457和320 mV，Tafel斜率分别为89和32 mV?dec^-1。本研究证明，B位Mo掺杂，对开发低成本、高性能的析氢和析氧双功能钙钛矿氧化物电催化剂具有一定实用价值。

Abstract:

Water electrolysis is a highly promising method for hydrogen（H₂）production，and it is a clean，efficient and safe technology. In the process of electrolytic water，the two endothermic half-reactions，anodic oxygen evolution reaction（OER）and cathodic hydrogen evolution reaction（HER），are kinetically slow and require high overpotentials to break through the energy barriers，which leads to high energy consumption. The use of efficient OER and HER catalysts is the key to improving the efficiency of water electrolysis. Therefore，the development of electrocatalysts with high activity，high stability，and low cost will greatly promote the industrialization of water electrolysis for H₂ production. Perovskite oxides have garnered widespread attention in the field of electrocatalysts for hydrogen evolution in water electrolysis due to their abundant element reserves and easy control of structure and composition. Doping of B-site ions in perovskite oxides is a common strategy to enhance their electrocatalytic activity. Carefully selecting the type and content of the B-site doping elements not only allows for the modulation of the crystal structure，leading to higher catalytic activity，but also imparts bifunctional catalytic properties to perovskite oxides. La_0.8Sr_1-xCo_xO_3-δ（LSCM，x =0，0.05，0.1 and 0.2）series of perovskite materials were prepared by solid-phase synthesis method using La_0.8Sr_0.2CoO_3-δ as the raw material through high-valent Mo ion doping. The effect of Mo doping（mass fraction）on the electrocatalytic OER and HER properties of perovskite materials was also investigated. The results show that：doping a small amount of Mo does not change the physical phase and microscopic morphology of LSCM，but can effectively enhance the OER and HER catalytic activities，due to Mo doping changes the valence state of Co，oxygen vacancies and the symmetry of the crystal structure，which affects the electrochemical catalytic performance of LSCM；a small amount of Mo doping has improved the OER and HER catalytic activities of LSC，but with the increase of Mo doping，the electrocatalytic performance of LSC is improved；when the Mo doping mass fraction is 5%，La_0.8Sr_0.2Co_0.95Mo_0.05O_3-δ（LSCM-5）possesses the best OER and HER catalytic activities，with OER and HER overpotentials of 457 and 320 mV and Tafel slopes of 89 and 32 mV?dec^-1，respectively，at a current density of 10 mA?cm^-2. This indicates that the practical value of B- site Mo doping in the development of cost-effective and high-performance bifunctional perovskite oxide electrocatalysts for both O₂ and H₂ evolution.