Platinum- and rhodium-enhanced electrocatalysis of hydrogen electrode reactions on cobalt in alkaline media

Abstract

Hydrogen electrode reactions are crucial processes regarding sustainable energy conversion technologies such as water electrolysis and fuel cells. In this study, we investigated the electrocatalytic activity of cobalt electrodes, whose surfaces were modified with noble metals – platinum (Pt) and rhodium (Rh) – towards the hydrogen evolution reaction (HER) and the hydrogen oxidation reaction (HOR) in alkaline media. The surface modification was achieved through a simple and rapid galvanic displacement process (30 seconds), enabling the efficient deposition of Pt and Rh onto polycrystalline cobalt electrodes, which resulted in a significant improvement in their electrocatalytic activity. Our results show that the Pt-modified electrode exhibited the highest activity for HER, surpassing even polycrystalline platinum, while the Rh-modified electrode also demonstrated substantial improvement compared to pure cobalt. However, for HOR, pure platinum retained superior electrocatalytic performance compared to the modified cobalt electrodes. These findings suggest that galvanic displacement of cobalt with Pt and Rh is an effective strategy to enhance HER kinetics and reduce noble metal utilization, offering a cost-efficient pathway for designing advanced electrocatalysts in hydrogen-based energy systems