Electrodeposited NiRh alloy as an efficient low-precious metal catalyst for alkaline hydrogen oxidation reaction

Abstract

Developing a non-precious or low Pt-group metal-containing (low-PGM) hydrogen oxidation reaction (HOR) catalyst is crucial to fabricate economic anion exchange membrane fuel cells (AEMFCs), an alternative to proton exchange membrane fuel cells (PEMFC). In this study, low-PGM Ni100-xRhx electrocatalysts, seldomly studied as alkaline HOR catalysts, with various compositions are fabricated via electrodeposition. Substantial changes are observed in both the morphology and crystalline structure of the catalysts when Ni is alloyed with Rh, such as enlarged surface area and development of different textures. The HOR activities of Ni100-xRhx catalysts evaluated in 0.1 M KOH solution are dramatically enhanced because of the enlarged surface area, bifunctional roles of H-providing sites (Ni/Rh) and OH-providing sites (Ni[OH](2)/Rh2O3), and their balanced composition on the surface. The durability of Ni89Rh11, the most appropriate catalyst, is investigated with the 3000 potential cycling, giving the average decay rate of approximately 0.30 mu A cm(-2)/cycle. The origin of enhanced activity and degradation during durability test was explained in terms of the electronic structures and surface composition of the catalysts. The initial high HOR activity of about 1.5 mA/cm(2) for Ni89Rh11 at 0.05 V-RHE, though it requires a further improvement in the durability, suggests the practical feasibility of it as a low PGM alkaline HOR catalyst.