3d–2p–5d Orbital Synergy in Electrocatalytic Hydrazine Oxidation Assisted Water Splitting with Industrial Scale Current Density

Abstract

The hydrazine oxidation reaction (HzOR) is a promising alternative to the oxygen evolution reaction (OER) in electrolyzers due to its lower oxidation potential than water, which significantly reduces energy demands and enhances hydrogen production efficiency. Incorporating high-valent 5d metals into 3d metal hydroxides has shown great potential for enhancing water-splitting performance through strong 3d–2p–5d orbital interactions, improving charge transfer, intermediate adsorption, and reducing overpotentials. This study showcases an innovative approach to enhance the electrocatalytic performance of Co(OH)₂ through the incorporation of a high-valent 5d metal, tungsten (W⁶⁺), using a straightforward electrochemical synthesis method. The incorporation of W⁶⁺ into Co(OH)₂ led to significant Co_3d–O_2p–W_5d orbital coupling, strengthening the electronic interactions between Co and W. The high-valent W⁶⁺ facilitated electron withdrawal from Co²⁺, promoting easier access to Co³⁺ sites enhancing the catalytic performance. The W-Co(OH)₂ achieved a current density of 100 mA cm^–2 at a potential of 1.00 V versus RHE for the HzOR, which is notably lower than the 1.54 V versus RHE required for the OER. In a two-electrode system, substituting OER with HzOR resulted in a significant reduction in cell voltage by 0.50 V.