image: Interfacial-induced stable CuO clusters for efficient electrochemical CO2-to-methane conversion
Credit: ©Science China Press
In the pursuit of sustainable solutions for energy and environmental challenges, electrochemical CO2 reduction reaction (CO2RR) stands out as a promising approach to convert CO2 into valuable products. Among these products, methane (CH4) is particularly significant due to its wide applications and high energy density. However, achieving efficient and stable CO2RR to CH4 remains challenging. Recently, a research team developed a CuO/MgO catalyst via a substrate-anchored thermal annealing strategy, which demonstrates exceptional performance in electrochemical CO2 methanation.
The CuO/MgO catalyst, especially the optimized CuO/MgO-2 with 1.25 wt.% Cu, showed remarkable activity and selectivity for CO2RR to CH4. It achieved a Faradaic efficiency (FE) of 82.3 % and a current density of 568.2 mA cm-2 at -1.0 V vs. RHE. Moreover, the catalyst exhibited outstanding long-term stability in a membrane electrode assembly (MEA) reactor, maintaining a CH4 FE of ~70 % at 500 mA cm-2 for 65 hours. Detailed in-situ characterizations and theoretical calculations revealed that the strong electronic metal-support interactions between CuO clusters and the MgO support played a crucial role. These interactions not only stabilized the Cu2+ sites but also optimized the adsorption energies of key intermediates, promoting the CH4 pathway and suppressing the formation of C2+ products.
The researchers used a substrate-anchored thermal annealing approach to synthesize the CuO/MgO catalyst. This method achieved homogeneous dispersion of CuO clusters on MgO nanosheets. The strong electronic interactions at the interface between CuO and MgO facilitated electron transfer from the MgO support to the CuO, enhancing the stability of CuO during the reduction reaction. The structural characterizations, including SEM, TEM, XRD, XANES, and XPS, confirmed the successful loading of CuO clusters on the MgO support and the strong electronic interactions between them.
In-situ X-ray absorption spectroscopy (XAS) and Raman experiments were conducted to investigate the structural and valence state changes of Cu elements under electrochemical CO2RR conditions. The results indicated that the CuO clusters on the MgO support remained stable throughout the CO2RR process due to the strong electronic metal-support interactions. Density functional theory (DFT) calculations further elucidated the reaction pathways and the effect of the strong electronic interactions on the adsorption energies of key intermediates.
This work provides valuable insights into the design of efficient and durable electrocatalysts for CO2RR. The CuO/MgO catalyst offers a promising solution for CO2 conversion, potentially contributing to carbon neutrality efforts. The findings highlight the importance of electronic metal-support interactions in enhancing catalytic performance and open new avenues for developing advanced electrocatalysts for CO2 methanation.