Cu,Nd-co-doped Co3O4 for efficient photothermal synergistic catalysis of CO2 hydrogenation at ambient pressure

Abstract

Utilizing renewable energy-derived H₂ to convert CO₂ into valuable chemicals represents a crucial strategy for achieving carbon emission reduction and enabling resource utilization. Conventional photocatalytic CO₂ methanation, however, is hindered by low activity and inefficient energy utilization, limiting its practical application. In the present work, we developed a Cu and Nd co-doped Co₃O₄ catalyst that synergistically harnesses both light and thermal energy for photothermal catalytic CO₂ methanation. The optimized catalyst with a molar ratio of 9/1/1 for Co/Cu/Nd (denoted as CCNO-9) achieves a remarkable CH₄ formation activity of 27.3 mmol g_cat⁻¹ h⁻¹ at 200 °C, especially at ambient pressure. The incorporation of foreign Cu and Nd atoms in Co₃O₄ lattice induces the formation of abundant heterogeneous interfaces and oxygen vacancies, thereby exposing additional active sites for CO₂ adsorption and activation. In situ DRIFTS studies revealed that the Nd promotes the conversion of CO₂ into *HCO₃⁻ and *COOH key intermediates. The photothermal synergy significantly enhances the reaction. Photoexcitation generates electrons and holes for CO₂ reduction, while the thermal energy assists in overcoming the reaction energy barriers. DFT calculations confirmed that the CCNO-9 catalyst requires the lowest energy barrier for the rate-determining step from *COOH to *CH₄. This study presents a very active and stable photothermal catalytic system for efficient CO₂ conversion, advancing the development of low-carbon catalytic technologies.