Atomically bridged palladium between nickel species and carbon microfibers and the subsequent conversion into free-standing and electrocatalytically active multifunctional electrodes

Abstract

Biomass-driven water electrolysis at low cell voltage represents an energy-efficient and environmentally friendly technology capable of simultaneously producing hydrogen and generating value-added chemicals. Designing highly active, multifunctional and cost-effective electrocatalysts for the oxidation of alcohols plays a significant role in the development of direct alcohol fuel cells and electrolyzers. Herein, we introduce free-standing multifunctional electrodes created by combining the atomic layer deposition of palladium (Pd) and nickel oxide (NiO) nanostructures directly onto gas diffusion electrodes (GDEs) and thermal treatment to form nanostructured electrocatalysts. We highlight the advantages of palladium–nickel based bimetallic nanostructured electrodes for the hydrogen evolution reaction (HER), ethanol oxidation reaction (EtOR), and glycerol oxidation reaction (GOR) in both half-cell and hydroxide anion exchange membrane (AEM) electrolyzer configurations. Although the metal loading is very low (20 μg_Pd cm⁻² and 47 μg_Pd+Ni cm⁻²), these electrodes demonstrate high current density at low potentials for the GOR and EtOR, as well as reduced overpotential during the HER. Integrating bimetallic GDE-Pd-Ni as anode and cathode electrodes into a biomass-fueled electrolyzer yields an efficient system. Specifically, GDE-Pd-Ni achieved 10 mA cm⁻² at 0.69 V and 100 mA cm⁻² at 1.10 V for an ethanol-fed electrolyzer at 50 °C, and 10 mA cm⁻² at 0.67 V and 100 mA cm⁻² at 1.21 V for a glycerol-fed electrolyzer at 70 °C. The present work could inspire the development of other energy materials as both the anode and the cathode in electrolyzers for electrosynthesis of fuels and high-value chemicals, promising a radical improvement in the current design of energy-efficient devices with a significantly reduced environmental footprint.