Highly efficient rhodium-decorated NiMoO4 nanorods as bifunctional catalysts for ammonia borane hydrolysis and electrooxidation: Experimental and DFT insights

Abstract

In this study, rhodium-decorated nickel molybdate (Rh/NiMoO4) nanorods are synthesized via a hydrothermalimpregnation reduction approach and systematically evaluated as bifunctional catalysts for ammonia borane (AB) hydrolysis and electrooxidation. Among the catalysts with different Rh loadings, the 4 wt% Rh/NiMoO4 catalyst exhibits the highest activity toward AB hydrolysis, achieving a hydrogen generation rate (HGR) of 504.5 mL H2 min-1 gcat-1 and a turnover frequency (TOF) of 883.16 min-1. Kinetic studies reveal a low activation energy of 33.26 kJ mol-1, indicating favorable reaction kinetics. Electrochemical measurements demonstrate superior AB electrooxidation performance for the 4 wt% Rh/NiMoO4 catalyst, characterized by enhanced specific and mass activities, reduced charge-transfer resistance, and excellent operational stability. This study presents a novel design of Rh-modified NiMoO4 nanorods as an efficient dual-functional catalyst for hydrogen production and electrooxidation applications, thereby distinguishing the present work from previously reported systems. Density functional theory (DFT) studies ensure molecular-level insight into the enhanced catalytic behavior, revealing strengthened metal-support interactions and a reduced HOMO-LUMO energy gap from 1.265 eV for pristine NiMoO4 to 1.234 eV for Rh/NiMoO4, indicative of developed electronic conductivity and charge-transfer capability.