Enhanced electrocatalytic nitrogen reduction on a three-dimensional Cu3P/SnP@CF catalyst through a multi-site synergistic effect between the heterointerface and phosphorus vacancies

Abstract

In the context of the energy crisis and sustainable development, the electrocatalytic nitrogen reduction reaction (NRR) for ammonia synthesis with zero-carbon emission characteristics holds great promise. However, the urgent and significant challenge is to develop highly efficient electrocatalysts with high ammonia yield and faradaic efficiency (FE). In this work, an efficient Cu₃P/SnP@CF catalyst with a heterojunction structure and phosphorus vacancies was successfully fabricated for the electrochemical reduction of nitrogen to ammonia through electrodeposition and thermal reduction methods. The Cu₃P/SnP@CF catalyst exhibited an ammonia yield of 68.2 μg h⁻¹ cm⁻² and a faradaic efficiency of 38%, with the ammonia synthesis rate remaining consistently stable over 6 cycles of testing, outperforming that of most reported similar catalysts. The improved electrocatalytic ammonia synthesis performance can be attributed to two key factors. First, it can be attributed to the well-matched and optimized tandem catalysis of N₂ adsorption and hydrogenation steps, whereby N₂ is significantly adsorbed on the catalyst surface with phosphorus vacancies, and then, the formation of a Cu₃P/SnP@CF heterojunction enhances strong interfacial electron interactions, lowers the energy barrier for the rate-limiting step of the NRR, and facilitates first nitrogen hydrogenation reactions, as confirmed by density functional theory calculations. Second, introducing p-block metals into transition (d-block) metal compounds can initiate p–d orbital hybridization; thus, the orbital hybridization effect accelerates electron transfer, increases the production rate of NH₃, and suppresses the competing hydrogen evolution reaction (HER). Moreover, a Zn–N₂ battery assembled with Cu₃P/SnP@CF showed an excellent power density of 8.17 mW cm⁻², which enabled simultaneous ammonia production and energy supply. This work demonstrates a promising approach to develop highly efficient electrocatalysts for sustainable ammonia production, with significant implications for addressing the energy crisis and promoting the transition towards a low-carbon economy.