Abstract
The electrochemical reduction of CO(2) (CO(2)RR) offers a promising route for sustainable fuel and chemical production. This study compares the CO(2)RR performance of hydrothermally synthesized carbon nanosphere-supported nickel hydroxide (Ni-C), copper hydroxide (Cu-C), and bimetallic nickel-copper hydroxide (NiCu-C) catalysts, investigating the influence of metal composition. Significant differences in product selectivity were observed: Cu-C primarily yielded C(2) products, whereas Ni-C and NiCu-C generated mixtures of H(2), CO, formate, and acetate, with minimal C(3) products. Faradaic efficiencies (FEs) for C(3) products (including propylene, propane, and n-propanol) were very low for Ni-C and NiCu-C (<0.3% combined). In comparison, Cu-C showed modest FEs (∼3-5%) primarily for n-propanol. X-ray photoelectron spectroscopy revealed partially oxidized nickel species (Ni (δ+)) in Ni-C and NiCu-C and predominantly Cu(i) species post-reaction, while scanning electron microscopy confirmed a distinct fibrous morphology for the Ni-containing catalysts. Control experiments with CO and acetate, and in situ Raman spectroscopy, suggest reaction pathways that differ from the typical Cu-catalyzed routes, potentially involving hydrogenated intermediates such as *CHO. This work provides a comparative analysis, highlighting how catalyst composition and associated electronic/structural properties influence the overall CO(2)RR activity and selectivity pathways in Ni, Cu, and NiCu hydroxide systems, rather than achieving significant C(3) production.