Copper-enhanced non-noble metal electrocatalysts for ammonia, urea, and hydrazine oxidation: Mechanistic and structural insights

This review examines the role of copper in enhancing the electrocatalytic oxidation of ammonia, urea, and hydrazine, which offer promising pathways for low-energy hydrogen production compared to conventional water electrolysis. Although non-noble metals are commonly employed due to their stability and promising catalytic activity in alkaline electrolytes, their performance remains limited by factors such as poor products selectivity and energy efficiency. Copper, as a dopant or alloying element, significantly improves these parameters through a number of mechanisms, including modulation of electronic structure (e.g., d-band centre shift), optimized adsorption energies, reduced reaction energy barriers, increased electrochemical surface area, and enhanced resistance to catalyst poisoning. Additionally, Cu facilitates charge transfer, elevates the valence state of Ni, and can form active species such as CuOOH, thereby accelerating the reaction kinetics. The results of experimental studies - supported by techniques such as cyclic voltammetry, electrochemical impedance spectroscopy and X-ray photoelectron spectroscopy, alongside calculations based on density functional theory, demonstrate the synergistic effects of Cu on non-noble metal-based electrocatalysts. These improvements establish Cu-modified catalysts as promising candidates for sustainable, decentralized hydrogen production and wastewater treatment. • Copper enhances non-noble electrocatalysts for ammonia, urea, and hydrazine oxidation. • Nine distinct Cu-induced mechanisms improve activity, selectivity, and stability. • Cu modifies adsorption energies, lowers activation barriers, facilitates charge transfer kinetics and limits by-products. • Cu-based systems enable low-energy hydrogen production and wastewater valorization.