Unveiling the Mechanism of Cr-Enhanced Oxygen Evolution Activities in Nickel Hydroxide

Nickel hydroxide (Ni(OH)₂) is regarded as one of the most promising oxygen evolution reaction (OER) catalysts due to its excellent catalytic performance and tunable electronic structure. In recent years, chromium (Cr) has demonstrated remarkable effectiveness in enhancing the OER performance of nickel-based materials due to its unique multiple valence states. However, the specific mechanism by which Cr³⁺ influences the OER performance of Ni(OH)₂ remains unclear, particularly its role in regulating the formation of reaction intermediates, which has not yet been fully elucidated. Herein, we employed a simple solution immersion method to successfully introduce various concentrations of Cr³⁺ onto the surface of Ni(OH)₂@NM. Experimental results demonstrate that the Cr³⁺-modified Ni(OH)₂@NM exhibits a remarkable improvement in OER performance, with the optimal sample showing a 110 mV reduction in overpotential at 10 mA cm^-2. Through systematic characterization and analysis, we found that the introduction of Cr³⁺ not only enhances the adsorption of OH* on the surface, which facilitates the OER process, but also significantly enhances the extent of surface oxidation of the catalyst during the OER process. This leads to a substantial increase in the number of active intermediates OOH*, thereby boosting the OER activity. This work provides a technical pathway for the development of simple and efficient OER catalysts.