Dual-functioning porous catalysts: robust electro-oxidation of small organic molecules and water electrolysis using bimetallic Ni/Cu foams

Abstract

In this work, we report a single-step preparation of porous Ni-based thin layer foams atop a Cu substrate via the facile dynamic hydrogen bubble template (DHBT) technique. As-prepared porous Ni-based foams were characterized by various electrochemical measurements, namely, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The prepared Ni foam has a cauliflower morphology, whereas the Ni/Cu foam obtained upon doping with Cu has a dendritic morphology. The latter foam layer possesses a higher exposed electroactive surface area and electrocatalytic performance than the undoped Ni foam, which depends on the percentage of Cu content. Additionally, the porous Ni/Cu foam shows marked performance as a dual catalyst towards cathodic and anodic reactions, i.e., hydrogen evolution reactions (HERs), oxygen evolution reactions (OERs), urea oxidation reactions (UORs), and glycerol oxidation reactions (GORs) in an alkaline medium. The co-deposition of Cu within the matrix of the Ni foam increases its intrinsic catalytic activity as evidenced by the enrichment of the Ni surface by electro-active species (catalytic mediators) as well as increasing the dispersion (and thus active surface area) of Ni within the porous foam layer. This Ni/Cu foam catalyst layer requires reduced overall energies of 1.71, 1.46, and 1.44 V to support 10 mA cm⁻² during overall water splitting, urea electrolysis, and glycerol electrolysis, respectively. Oxalate is the main byproduct resulting from glycerol electrolysis as revealed by the FTIR analysis.