Carbon-Based Catalysts for Hydrazine Oxidation Reaction: A Promising Low-Energy Route for Hydrogen Generation Beyond Conventional Water Splitting

Abstract

Hydrogen is gaining momentum as a clean, high-energy-density alternative to fossil fuels, with green hydrogen production offering a pathway to zero-carbon energy systems. Conventional water splitting, comprising the hydrogen evolution reaction (HER) at the cathode and the oxygen evolution reaction (OER) at the anode, suffers from the intrinsic sluggishness of the OER a kinetically demanding four-electron process requiring a high overpotential (1.23 V vs. RHE). Replacing the OER with the hydrazine oxidation reaction (HzOR), a thermodynamically favourable process with faster kinetics, can markedly improve energy efficiency in electrolytic hydrogen production. This review focuses on carbon-based electrocatalysts as a sustainable platform for HzOR, with particular attention to their coordination chemistry features. Strategies such as heteroatom doping (N, S, P, B) and incorporation of transition-metal centres (Fe, Co, Ni, Cu) into carbon lattices generate well-defined coordination environments most notably M-N x sites that modulate the electronic structure, enhance hydrazine adsorption, and lower activation barriers. The influence of coordination geometry, ligand field effects, and metalligand orbital interactions on reaction pathways is discussed alongside synthetic approaches, including MOF-derived carbons, which allow atomic-level control over active site distribution. Furthermore, we examine the interplay between interfacial charge transfer and catalytic stability, and highlight the use of theoretical modelling and machine learning to predict and optimise coordination environments. By integrating fundamental coordination chemistry with materials engineering, this review underscores the potential of rationally designed carbonbased catalysts to drive HzOR efficiently, paving the way for scalable, sustainable green hydrogen generation.