High-Performance NiCu Hydroxide Self-Supported Electrode as a Bifunctional Catalyst for AOR and OER

Abstract

Ammonia has gained considerable attention as a promising energy carrier due to its high hydrogen content, carbon-free emissions, and ease of storage and transportation compared to hydrogen gas. The electrochemical ammonia oxidation reaction (AOR) is a pivotal process for harnessing ammonia as a sustainable energy source, enabling hydrogen production through ammonia decomposition or electricity generation via direct ammonia fuel cells. NiCu, a transition metal alloy, has shown great potential as an efficient and cost-effective catalyst for AOR. In this study, high-valence Ni and Cu hydroxyl hydroxides were synthesized on nickel foam to form NiCuOOH in the structure of folded nanosheets, serving as an anodic electrocatalyst for AOR. Comprehensive characterization identified high-valence metals as the primary active components. By optimizing the Ni/Cu ratio, the catalyst achieved remarkable performance and stability, reaching a maximum current density of 169 mA cm⁻² at 1.62 V versus RHE, with 0.16 at% Cu delivering high ammonia oxidation activity, and being stable for 48 h at 100 mA cm⁻². Additionally, the catalyst exhibited excellent catalytic activity for the oxygen evolution reaction (OER), attaining a maximum current density of 152 mA cm⁻² at 1.72 V versus RHE. This study presents a cost-effective, high-performance, and easily synthesized bifunctional self-supporting catalyst, offering significant potential for both AOR and OER applications.