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.