Hydrogen spillover-driven selective hydrogenation of nitrobenzoic acid to aminobenzoic acid over a ZIF-8/Cu(OH)2 heterostructure

Abstract

The electrocatalytic conversion of toxic p-nitrobenzoic acid (PNBA) into valuable p-aminobenzoic acid (PABA) offers a promising strategy for environmental remediation and resource recovery. Here, we fabricate a ZIF-8/Cu(OH)₂/CF composite electrode via a two-step in situ growth method, effectively combining the merits of ZIF-8, Cu(OH)₂ and conductive copper foam (CF). Under optimized neutral conditions (−0.345 V vs. RHE, 50 mM PNBA in 1.0 M PBS), the catalyst achieves >99% PNBA conversion, 98% PABA selectivity, and 95% Faradaic efficiency, markedly surpassing CF and Cu(OH)₂/CF controls. Structural analyses (XRD, XPS, and HRTEM) confirm the formation of a heterointerface and reveal synergistic interactions between ZIF-8 and Cu(OH)₂. Electrochemical assessments (LSV, EIS, and Tafel) attribute the enhanced activity to an expanded electroactive surface area (C_dl = 35.31 mF cm⁻²), accelerated charge transfer, and reduced energy barriers. In situ ATR-FTIR, EPR, and kinetic studies identify the hydrogenation of PNBA to p-nitrosobenzoic acid as the rate-determining step, facilitated by hydrogen spillover from ZIF-8 to Cu(OH)₂ via water dissociation. The catalyst can be efficiently regenerated while retaining its phase structure and performance. This work presents a viable design approach to high-performance, recyclable electrocatalysts for nitroarene reduction, leading to the advancement of sustainable fine chemical synthesis.