Construction of a Cu3+–OH–Pt interface for enhancing glycerol electrooxidation coupled with hydrogen evolution†

Abstract

The electrochemical conversion of glycerol, a biodiesel byproduct, into formic acid coupled with the hydrogen evolution reaction (HER) offers a green route for biomass utilization. However, existing systems suffer from high energy demands and insufficient selectivity. Herein, a self-grown copper oxide nanorod catalyst decorated with platinum species (Pt/CuO NRs) is developed, reaching a current density of 20 mA cm⁻² at 1.14 V vs. RHE, with 97.4% formic acid selectivity at 1.40 V vs. RHE and nearly 100% glycerol conversion. Electrochemical impedance spectroscopy and in situ Raman spectroscopy reveal that the introduction of Pt⁰ enhances electron transfer at the Cu³⁺–OH–Pt interface, facilitating Cu^III–OOH formation. Density functional theory (DFT) analysis shows that Pt weakens the O–H bond strength in CuOOH and lowers the dehydrogenation energy barrier, synergistically boosting the glycerol oxidation reaction (GOR). Furthermore, a membrane electrode assembly (MEA) using Pt/CuO NRs as the anode and Pt/CuO_x (c-Pt/CuO_x) as the cathode is established for the GOR and HER, respectively, and it can operate at 1.55 V for a current density of 100 mA cm⁻², reducing the potential by 380 mV compared to that required for water splitting. The developed GOR(+)||HER(−) electrolyzer demonstrates stable performance for 100 hours at 150 mA cm⁻², with a formic acid selectivity of 90%. This represents a significant improvement over existing copper-based catalysts, highlighting the green chemistry advantages. Techno-economic analysis demonstrated the economic viability of electrochemically converting glycerol into potassium dicarboxylate (KDF) and H₂, with processing costs of $4655–4797 per ton and a market value of $6389 per ton at representative commercial current densities of 100 and 300 mA cm⁻².