The electrocatalytic oxidation of urea (EOU) is an important half-reaction in water splitting, urea fuel cells, and urea wastewater treatment. The anions of nickel-based catalysts can be leached severely in the oxidation potential range. Therefore, the influence of anion on the electrocatalytic performance of Ni(OH)₂/NiOOH for urea oxidation has not been systematically studied. The present experimental results show that the structure reconstruction of catalyst is a complicated process, specifically including deep penetration by alkaline electrolyte, leaching-induced oxidation by phosphorus or sulfur anions, transformation or cracking of the original structure, and formation of an amorphous layer on the surface. The reconstructed NF-NiP_x-R or NF-NiS_x-R has a three-layer core-shell structure, with a nickel foam skeleton in the innermost layer, an amorphous NiP_x or NiS_x layer in the middle layer, the outermost layer of oxygen-containing anion (PO_x or SO_x) coordinated Ni(OH)₂. In the prepared catalyst, the Ni(OH)₂/NiOOH redox is the real catalytic species for the urea oxidation. It is found that the oxygen-containing anion can enhance the catalytic performance of the Ni(OH)₂/NiOOH redox, and PO_x anion has the best enhancing effect. It is found that the urea molecules are oxidized on the electrocatalyst surface mainly through an indirect pathway.

中文翻译：

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含氧阴离子促进Ni(OH)2/NiOOH尿素氧化的电催化活性

尿素电催化氧化（EOU）是水分解、尿素燃料电池和尿素废水处理中重要的半反应。镍基催化剂的阴离子在氧化电位范围内会被严重浸出。_{因此，阴离子对Ni(OH) 2} /NiOOH尿素氧化电催化性能的影响尚未系统研究。目前的实验结果表明，催化剂的结构重构是一个复杂的过程，具体包括碱性电解液的深度渗透、磷或硫阴离子浸出诱导的氧化、原始结构的转变或裂解以及在催化剂上形成非晶层。表面。重构的NF-NiP _x -R或NF-NiS _x -R具有三层核壳结构，最内层为泡沫镍骨架，中间层为非晶态NiP _x或NiS x层，最外层为非晶态NiP x或NiS _x层。含氧阴离子(PO _x或SO _x )配位Ni(OH) ₂层。在制备的催化剂中，Ni(OH) ₂ /NiOOH氧化还原剂是尿素氧化的真正催化物种。结果发现，含氧阴离子可以增强Ni(OH) ₂ /NiOOH氧化还原的催化性能，其中PO _x阴离子的增强效果最好。研究发现尿素分子在电催化剂表面的氧化主要通过间接途径。