Rh₂S₃/N-Doped Carbon Hybrids as pH-Universal Bifunctional Electrocatalysts for Energy-Saving Hydrogen Evolution

Using hydrazine oxidation reaction (HzOR) to replace the oxygen evolution reaction is an effective way to decrease the overpotential of the anodic reaction in overall water splitting (OWS), facilitating cost-effective and safe hydrogen production. Herein, Rh₂S₃/N-doped carbon hybrids (Rh₂S₃/NC) are first reported as novel and efficient bifunctional electrocatalysts for hydrazine-assisted hydrogen generation over a wide pH range. Specifically, Rh₂S₃/NC exhibits low overpotentials for the hydrogen evolution reaction (HER) in alkaline (38 mV), neutral (46 mV), and acidic (21 mV) electrolytes, to reach the current density of 10 mA cm⁻², and maintains the activities over 70 h. Meanwhile, Rh₂S₃/NC also displays competitive HzOR performance at all-pH electrolytes. Thus, serving as a bifunctional electrocatalyst for both HER and HzOR, Rh₂S₃/NC shows overwhelming-Pt/C performance in three electrolytes, and can save over 93.3%, 85.2%, and 78.3% energy consumption compared to the corresponding OWS system. Moreover, theoretical calculations confirm that Rh₂S₃/NC owns low free-energy changes of the H adsorption and the dehydrogenation of adsorbed NHNH both of which are beneficial to enhance catalytic activity. This work develops a novel bifunctional electrocatalyst with free pH-dependent condition for the hydrazine-assisted electrolysis system to furtherly reduce the cost of massive industrial H₂ production.