Conjugated coordination polymer composite electrodes for efficient nitrogen reduction electrocatalysis

Abstract

Electrocatalytic nitrogen reduction reaction (NRR) in alkaline electrolyte presents a sustainable pathway for energy storage and green ammonia (NH₃) synthesis under ambient conditions. Recent studies have shown that adjust d band center of metal active sites can modulate the adsorption/activation energies of reactant and further affect their electrocatalytic performances. Among other NRR catalysts, single-atom catalysts have recently recognized as a promising candidate owning to its maximum metal-utilization efficiency and well-defined active sites, thus can adjust the d band center of metal active sites in the single-atom catalysts. Herein, the catalytic activities of conjugated coordination polymer composite electrodes toward NRR catalysis with respect to the d band center are explored, where four composite electrodes with different metal active sites (including Fe, Co, Ni and Cu) are investigated. Through X-ray photoelectron spectroscopy, valence band spectra analysis and electrochemical measurements, it is found that the d band center in these composite electrodes surprisingly exhibit a same trend in their activities toward NRR catalysis. A higher d band center can appreciably promote the absorption/activation of N₂, leading to its improved NRR performance.