The development of highly active electrocatalysts is essential to the commercialization of water splitting. Introducing ligand of foreign metals is a promising approach to optimize the electronic structure of electrocatalyst and regulate chemisorption behavior of intermediate species.Herein, Ru(OH) x Cl y cluster−modified CoNi alloy nanoparticles encapsulated in nitrogen-doped graphene (Ru-CoNi@NC-X) was prepared by a partial galvanic replacement method. The electrochemical results indicated that a moderated Ru(OH) x Cl y cluster was beneficial to improve the both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) properties of CoNi alloy nanoparticles (CoNi@NC).

Optimizing the surface structure at the atomic scale is crucial for developing effective catalysts. In this work, a hybrid material consisting of well-dispersed sub-nanometer-sized (SNS) iridium (Ir) species decorated on mesoporous Co 3 O 4 was fabricated as electrocatalyst for the oxygen evolution reaction (OER) through pyrolysis of IrCl 3 /Co(NO 3 ) 2 complexes confined within the mesoporous KIT-6 template. It was found that the KIT-6 template played a critical role in the formation of SNS Ir species. The optimized IrÀ Co 3 O 4 -1 showed highly efficient OER catalytic performance with an overpotential of 1.527 V to achieve the current density of 10 mA cm À 2 , and superior stability in alkaline condition. The electrochemical results demonstrated that moderate Ir incorporation was conductive to form the high valence Co ions in form of Co oxyhydroxide during the OER process. The present work would open a new route for material design of SNS Ir species decorated mesoporous metal oxides for the application in catalysis.