Rh/RhOx nanosheets as pH-universal bifunctional catalysts for hydrazine oxidation and hydrogen evolution reactions

Abstract

Hydrazine oxidation reaction (HzOR)-assisted hydrogen evolution is a promising effluent treatment and energy conversion method for resolving the global energy shortage and environmental crisis. However, highly efficient and pH-universal electrocatalysts are still lacking to boost the sluggish kinetics of both the cathodic hydrogen evolution reaction (HER) and anodic HzOR. Here, Rh/RhO_x nanosheets with Rh–O–Rh interfaces are fabricated by alkali-assisted synthesis and the H₂ reduction route. When they are employed as efficient bifunctional electrocatalysts, the Rh/RhO_x nanosheets exhibit outstanding performance and stability for the HER and HzOR in pH-universal electrolytes. The two-electrode electrolyzer delivers a current density of 10 mA cm⁻² with an ultra-low voltage of 0.068, 0.268, and 0.348 V in 1.0 M KOH/0.5 M N₂H₄, 1.0 M PBS/0.3 M N₂H₄ and 0.5 M H₂SO₄/0.5 M N₂H₄, respectively. The performance can be maintained over 65 h for the HER and HzOR under neutral conditions. Density functional theory calculations indicate that the high activity is derived from the Rh–O–Rh interfaces. The regulation of the interface greatly improves the activity of the catalyst and reduces energy consumption, which is more conducive to the production of hydrogen.