Regulating three-dimensional morphology and surface functionality of cu/Cu2+1O@PANI electreocatalyst enables the conversion of nitrate to ammonia

Abstract

The electrocatalytic nitrate reduction reaction (NO₃RR) offers substantial potential for ammonia energy storage and conversion. However, the low adsorption capacity of nitrate and the key competition between hydrogen evolution reaction and NO₃RR suppress the electrocatalytic reduction of NO₃⁻ to NH₃. Here, we develop a novel Cu/Cu₂₊₁O@PANI electrocatalyst by coupling nitrate-selective electrosorption material (polyaniline, PANI) with CuO inverse opals (CuO IOs) through in-situ electroreduction. The synergy of three-dimensional morphology and PANI functionality optimizes nitrate enrichment and activates hydrogen (*H) accumulation. Thanks to these advantages, the optimized Cu/Cu₂₊₁O@PANI exhibits excellent NO₃RR performance with a Faradaic efficiency (FE) of 90.89% and a maximum NH₃ yield of 0.2846 mmol h⁻¹ cm⁻². Finite element analysis (FEA) and density functional theory (DFT) calculations reveal that the 3D porous structure enhances the local concentration of NO₃⁻, whilst the functional interface of Cu/Cu₂₊₁O@PANI promotes the generation of *H and facilitates the formation of reaction intermediates (*NOH), thereby ensuring improved reaction selectivity.