Key Takeaways & Executive Findings
- •• • Cu/Cu2O@CF achieves 100 mA cm−2 at an ultra-low potential of −0.05 V vs. RHE, outperforming most reported FOR catalysts and enabling energy-efficient operation. • • The catalyst sustains 735 mA cm−2 at 0.6 V vs. RHE, overcoming the deactivation limit of conventional Cu-based catalysts above 0.5 V, ensuring high-current durability. • • Faradaic efficiencies for both formate and H2 production approach ~100%, indicating near-quantitative conversion of formaldehyde to valuable products. • • Coupling FOR with HER reduces hydrogen production energy consumption to 0.57 kWh m−3 H2, significantly lower than traditional water electrolysis, offering a cost-effective route for industrial hydrogen generation.
Abstract
Formaldehyde oxidation reaction (FOR) demonstrates significant potential in energy conversion and chemical synthesis, yet developing catalysts for efficient operation at high current densities remains a challenge. Herein, we fabricated a Cu/Cu2O heterostructure nanowire catalyst on copper foam (Cu/Cu2O@CF) via interface engineering and investigated its FOR performance. Electrochemical tests show that Cu/Cu2O@CF exhibits excellent activity: it achieves 100 mA cm−2 at an ultra-low potential of −0.05 V (vs. RHE), outperforming most reported catalysts. Notably, this catalyst overcomes the deactivation limitation of conventional Cu-based catalysts above 0.5 V, maintaining a current density of 735 mA cm−2 at 0.6 V with excellent stability during long-term electrolysis. SCN−-induced Cu0 poisoning experiments confirm that Cu/Cu2O@CF retains a Cu/Cu2O mixed structure at 0.6 V, where Cu0-Cu+ synergy dominates its high activity. Density functional theory (DFT) calculations reveal two key advantages of this structure: it weakens OH− adsorption to avoid active site occupation, and reduces C–H bond cleavage barriers while promoting H* combination into H2. Product analysis shows Faradaic efficiencies for formate and H2 production are both ~100%. When coupled with the hydrogen evolution reaction (HER), the system's hydrogen production energy consumption is as low as 0.57 kWh m−3 H2, much lower than traditional water electrolysis. This work elucidates the regulatory mechanism of interface engineering on the FOR performance of Cu-based catalysts, expands the application of Cu-based heterostructures in high-current FOR, and guides the development of industrial-grade electrocatalysts.
1. Introduction
Formaldehyde electrooxidation (FOR) presents a low-potential alternative to the oxygen evolution reaction (OER) in water electrolysis, addressing the high energy losses that hinder conventional hydrogen production. Formaldehyde, a volatile organic pollutant, can be oxidized at a thermodynamic potential of only −0.22 V vs. RHE, simultaneously degrading waste and generating high-value formate and hydrogen. Coupling FOR with the hydrogen evolution reaction (HER) enables dual hydrogen production at both anode and cathode, drastically reducing the electricity consumption for H2 generation. However, the practical implementation of FOR is constrained by the lack of efficient, stable catalysts that operate at high current densities.
Metallic copper is an ideal candidate due to its low cost and high conductivity, yet pure Cu catalysts exhibit inadequate activity and deactivate at potentials above 0.5 V, limiting their industrial applicability. The bottleneck lies in the weak adsorption and activation of formaldehyde on Cu surfaces, coupled with strong OH− adsorption that blocks active sites. This study introduces a Cu/Cu2O heterostructure nanowire array on copper foam via interface engineering, which synergistically enhances C–H bond cleavage while suppressing OH− adsorption. The resulting catalyst achieves exceptional activity and stability at high current densities, providing a viable pathway for industrial-scale formaldehyde oxidation and energy-efficient hydrogen production.
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Lv Weixin, Pan Linlin, Zhang Xu, Wang Chongchong, Wei Meijie, Zhang Rui, Wang Wei, Wang Lei (2026). Interface Engineering of Cu/Cu2O Nanowires on Cu Foam: Boosting C–H Bond Cleavage and Suppressing OH− Adsorption for Efficient Formaldehyde Electrooxidation. SCIENCE CHINA Materials. https://doi.org/10.1007/s40843-025-3880-8
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Frequently Asked Questions
What is the specific role of the Cu/Cu2O interface in enhancing FOR activity and stability?
The Cu/Cu2O interface facilitates a synergistic Cu0-Cu+ effect that weakens OH− adsorption, preventing active site blockage, and lowers the C–H bond cleavage barrier, promoting H* combination into H2. This dual mechanism enables high activity (100 mA cm−2 at −0.05 V) and stability up to 0.6 V (735 mA cm−2), overcoming the deactivation seen in pure Cu.
How does the catalyst perform under long-term electrolysis at high current densities?
Cu/Cu2O@CF maintains excellent stability during long-term electrolysis at 0.6 V, sustaining 735 mA cm−2 without significant degradation, as confirmed by SCN− poisoning experiments that show retention of the mixed Cu/Cu2O structure.
What are the Faradaic efficiencies for formate and H2, and what implications do they have for industrial application?
Both formate and H2 production exhibit ~100% Faradaic efficiency, indicating near-quantitative conversion of formaldehyde. This high selectivity is crucial for industrial processes to minimize byproduct formation and maximize product yield.
How does the energy consumption for hydrogen production compare to traditional water electrolysis?
When coupled with HER, the system achieves a hydrogen production energy consumption of only 0.57 kWh m−3 H2, significantly lower than conventional water electrolysis (typically >4.5 kWh m−3), offering a cost-effective route for industrial hydrogen generation.
What is the scalability potential of this Cu/Cu2O@CF catalyst for industrial formaldehyde oxidation?
The catalyst is fabricated on copper foam, a low-cost and scalable substrate, and operates at high current densities (735 mA cm−2) with excellent stability, making it suitable for industrial-scale electrolyzers. The ultra-low potential and high Faradaic efficiency further enhance its economic viability.
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