Simple routes for the improvement of hydrogen evolution activity of Ni-Mo catalysts: From sol-gel derived powder catalysts to graphene supported co-electrodeposits

Abstract

Development of noble metal-free catalysts for hydrogen production is one of the cores of the sustainable energy economy. Here we present results of systematic analysis of catalytic activity of Ni-Mo alloy powders in alkaline media towards hydrogen evolution reaction (HER). Catalysts were prepared in a wide concentration range (from Ni0.2Mo0.8 to Ni0.9Mo0.1), and resulted with a volcano shaped activity-composition relationship, with maximum catalytic activity achieved for the powder with nominal composition Ni0.6Mo0.4. Improved HER activity is ascribed to reduced deactivation by hydride formation and adequate hydrogen-surface energetics on Ni-Mo catalysts. In the second part, we demonstrate a novel method for electrochemical formation of NiMo@rGO composites. Prepared composite electrodes show improved electrocatalytic activity compared to both pure Ni and Ni@rGO electrodes. Activity was observed to depend on the deposition time and is contributed by two factors: (i) formation of Ni-Mo system and (ii) formation of an interfacial region with rGO. We expect that the provided activity-composition relationship in combination with novel electrochemical NiMo-rGO composite formation procedure will provide a route for the development of new highly efficient noble metal-free HER electrocatalysts.