Controllable partial self-sacrifice of metal-organic frameworks for enhancing nitrate electroreduction to ammonia

Abstract

Electrochemical nitrate reduction to ammonia (NO₃RR) is the most promising pathway for the value-added conversion of nitrate. However, the NO₃RR process involves the transfer of multi-electrons and protons and hence suffers from slow kinetics, leading to an urgent need to develop high-performance NO₃RR catalysts. Here, we prepare ultrafine Cu₂O particles in situ generated and encapsulated in metal-organic frameworks (MOFs) containing coordination-unsaturated Cu²⁺ nodes by the controlled self-sacrifice of a selected part of the framework. The composite catalyst achieves the impressive catalytic performance for NO₃RR, with an NH₃ yield rate of 6.35 mmol h⁻¹ mg_cat⁻¹ and corresponding Faraday efficiency of 98.6%. Density functional theory (DFT) calculations demonstrate that the synergistic effect between unsaturated Cu²⁺ nodes and nanoparticles markedly decreases the potential energy of all intermediates, thereby facilitating an efficient conversion of nitrate to ammonia.