Sulfate-Decorated Amorphous–Crystalline Cobalt-Iron Oxide Nanosheets to Enhance O–O Coupling in the Oxygen Evolution Reaction

作者：Xiang Wang, Junshan Li, Qian Xue, Xu Han, Congcong Xing, Zhifu Liang, Pablo Guardia, Yong Zuo, Ruifeng Du, Ll. Balcells, Jordi Arbiol, Jordi Llorca, Xueqiang Qi, Andreu Cabot · 发表于：ACS Nano · 年份：2022 · DOI：10.1021/acsnano.2c12029 · 被引用次数：109 · 研究领域：Electrocatalysts for Energy Conversion、Electrochemical Analysis and Applications、Advanced battery technologies research

The electrochemical oxygen evolution reaction (OER) plays a fundamental role in several energy technologies, which performance and cost-effectiveness are in large part related to the used OER electrocatalyst. Herein, we detail the synthesis of cobalt-iron oxide nanosheets containing controlled amounts of well-anchored SO 4 2– anionic groups (CoFe x O y -SO 4 ). We use a cobalt-based zeolitic imidazolate framework (ZIF-67) as the structural template and a cobalt source and Mohr’s salt ((NH 4 ) 2 Fe(SO 4 ) 2 ·6H 2 O) as the source of iron and sulfate. When combining the ZIF-67 with ammonium iron sulfate, the protons produced by the ammonium ion hydrolysis (NH 4 + + H 2 O = NH 3 ·H 2 O + H + ) etch the ZIF-67, dissociating its polyhedron structure, and form porous assemblies of two-dimensional nanostructures through a diffusion-controlled process. At the same time, iron ions partially replace cobalt within the structure, and SO 4 2– ions are anchored on the material surface by exchange with organic ligands. As a result, ultrathin CoFe x O y -SO 4 nanosheets are obtained. The proposed synthetic procedure enables controlling the amount of Fe and SO 4 ions and analyzing the effect of each element on the electrocatalytic activity. The optimized CoFe x O y -SO 4 material displays outstanding OER activity with a 10 mA cm –2 overpotential of 268 mV, a Tafel slope of 46.5 mV dec –1, and excellent stability during 62 h. This excellent performance is correlated to the material’s structura...