Dilute Alloying-Induced d-p Orbital Hybridization in Pd-Bi Metallene Arrays for Electrocatalytic Coupling of Carbon Dioxide and Nitrate to Urea

Abstract

Electrocatalytic urea synthesis from CO2 and NO3− offers a dual solution for greenhouse gas mitigation and industrial effluent valorization, while enabling renewable energy storage. Rational design of advanced catalysts for urea electrosynthesis represents a scientifically critical yet persistently challenging endeavor. In this study, we developed Pd-Bi dilute alloy metallene arrays grown on Cu foam (Pd-Bi/CF) by a two-step galvanic replacement strategy. The optimized Pd10-Bi90/CF could deliver a notable urea yield rate of 2165.2 μg h-1 cm-2 with 45.3% Faradaic efficiency at −0.25 V vs. reversible hydrogen electrode (RHE). Experimental and computational studies validated that d-p orbital hybridization between d-block Pd and p-block Bi in Pd10-Bi90/CF modulates the electronic structure of active sites, thereby facilitating adsorption and activation of NO3− and CO2, synergistic generation of key intermediates *NH2 and *CO, and selective C-N coupling toward urea synthesis. This study demonstrates a viable pathway toward optimizing Bi-based catalysts for electrocatalytic urea synthesis.