Solar Self-Driven Electrocatalytic Reduction of N₂ Directly to CO₂-Free Generation of Ammonia on a Coupled Ce-Mediated Cu/Porous Carbon Electrode

Abstract

Reduction of nitrogen to ammonia under mild conditions is recognized as one key step in the NH3-economy. The Haber–Bosch process, the typical ammonia production technique, is energy-intensive and high carbon-emitting. Intense efforts have been devoted to searching for sustainable options for decarbonized ammonia generation. Wherein, the electrocatalytic nitrogen fixation route driven by renewable energy is extremely anticipated. Herein, the integrated concept for ammonia production powered by direct solar energy is outlined and proposed. Responding to the limited yield rate and reasonable Faraday efficiency in ammonia synthesis, non-precious Cu-electrocatalysts with porous carbon as substrates are fabricated and Ce is introduced as a modulator which could facilitate electron conduction and nitrogen trapping. By optimizing the proportion of metal sources, strongly synergistic metallic effect of Ce and Cu is structured, further enhancing nitrogen reduction performance of electrocatalysts and inhibiting hydrogen evolution reaction. A satisfactory NH3 yield rate of 30.60 ± 3.04 μg h–1 mgcat –1 is achieved at −0.3 V vs reversible hydrogen electrode (RHE) in 0.1 M KOH and the corresponding FE is about 8.20 ± 0.22%. The solar self-driven NH3 generation system presents a total yield of 104 μg mgcat –1 and a solar-to-ammonia efficiency of 1% at ∼1.2 V in daylight. This work offers a rational energy-utilizing strategy for the preparation of high-grade NH3 chemical via solar system employing non-precious metal catalysts in zero-carbon emission footprint.