Morphology and electronic structure modulation of Cu-doped Co₃O₄/rGO nanosheets for efficient electrocatalytic nitrate-to-ammonia upcycling and onsite chalcone synthesis.

Abstract

Electrocatalytic nitrate reduction (NO₃RR) offers a promising route for ammonia synthesis, but is hindered by slow kinetics and competitive hydrogen evolution reaction (HER). Herein, ultrathin Cu-doped Co₃O₄/reduced graphene oxide (Cu-Co₃O₄/rGO) nanosheets are prepared through the morphology and electronic structure modulation for efficient NO₃RR performance. Combined experiments and DFT computations disclose that Cu doping induces 2D nanosheet morphology, up-modulates the d-band center to optimize the adsorption strength of reactants and key intermediates, and constructs CuCo tandem sites for cascade catalysis, while rGO improves the composite conductivity. The optimized catalyst exhibits a Faradaic efficiency of 98.5% at -0.7 V vs. RHE and an ammonia yield of 25.2 mg h-1 mgcat-1 at -1.0 V vs. RHE with high stability. The in-situ electro-generated ammonia acts directly as a base catalyst for chalcone synthesis with 75.9% conversion, constructing a waste-to-resource-to-value model integrating nitrate remediation and sustainable fine-chemical synthesis.

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