Biomass upgrading coupled with H2 production via a nonprecious and versatile Cu-doped nickel nanotube electrocatalyst

Abstract

Coupling oxidative biomass valorization with H₂ production in a hybrid water splitting configuration is of significant importance to yield sustainable and value-added carbon products. Herein, we report an earth-abundant alloy catalyst, Cu-doped Ni nanotubes (NiCu NTs), through a simple electrodeposition-dealloying route, which acts as a competent catalyst for the electrocatalytic oxidation (ECO) of 5-hydroxymethylfurfural (HMF) at the anode and simultaneous cathodic H₂ evolution. The cell potential required to deliver a benchmark current density of 100 mA cm⁻² is greatly decreased by 350 mV with respect to the conventional overall water splitting, demonstrating a better energy consumption efficiency. When being employed as an anodic catalyst, the NiCu NTs catalyst enables ∼100% conversion of HMF and ∼99% yield of 2,5-furandicarboxylic acid (FDCA) with 20 mM HMF in 1.0 M KOH, and a good-to-excellent product yield can be obtained at an increased HMF concentration from 35 to 100 mM. The potential-dependent Raman results reveal that the electrogenerated Ni³⁺OOH species are the intermediates to promote HMF oxidation. Moreover, the catalyst also delivers almost ∼100% conversion and selectivity to the corresponding acid products when extending the organic substrates to other small alcohols/aldehydes, demonstrating its splendid versatility.