High-valence molybdenum-induced boundary-rich heterostructures for enhanced oxygen evolution reaction

The green synthesis of hydrogen through electrochemical water splitting has been severely limited by the slow kinetics of the anodic oxygen evolution reaction (OER). However, the current benchmark electrocatalysts are still based on precious metals. Therefore, developing low-cost and highly efficient OER electrocatalysts is of great importance. Here, we design nanoscale multicomponent metal flakes with a crystalline/amorphous structure (ac-FeCoNiMo) via a simple sol-gel strategy to enhance OER performance. By engineering the structure through a high-valence Mo doping strategy, we successfully develop ac-FeCoNiMo with a unique architecture featuring boundary-rich regions, modulated Fe/Co species, defects, and enlarged metal-O bonds. As a result, the optimized ac-FeCoNiMo exhibits excellent electrochemical OER performance, achieving low overpotentials of 222 mV and 253 mV to reach current densities of 20 and 100 mA cm⁻², respectively, along with outstanding stability. Mechanistic investigations reveal that ac-FeCoNiMo follows the Lattice Oxygen Mediated (LOM) mechanism during the OER process. This behavior is likely due to the induced weakening of metal-oxygen bonds, resulting from the expanded M-O-M (M = metal) units and the formation of abundant boundary-rich regions. This study paves the way for the development of highly efficient multi-element electrocatalysts.