Spatial Structure of Electron Interactions in High-entropy Oxide Nanoparticles for Active Electrocatalysis of Carbon Dioxide Reduction.

High-entropy oxides (HEOs) exhibit distinctive catalytic properties owing to their diverse elemental compositions, garnering considerable attention across various applications. However, the preparation of HEO nanoparticles with different spatial structures remains challenging due to their inherent structural instability. Herein, ultrasmall high-entropy oxide nanoparticles (less than 5 nm) with different spatial structures are synthesized on carbon supports via the rapid thermal shock treatment. The low-symmetry HEO, BiSbInCdSn-O, demonstrates exceptional performance for electrocatalytic carbon dioxide reaction (eCORR), including a lower overpotential, high Faraday efficiency across a wide electrochemical range (-0.3 to -1.6 V), and sustained stability for over100 h. In the membrane electrode assembly electrolyzer, BiSbInCdSn-O achieves a current density of 350 mA cm while maintaining good stability for 24 h. Both experimental observations and theoretical calculations reveal that the electron donor-acceptor interactions between bismuth and indium sites in BiSbInCdSn-O enable the electron delocalization to facilitate the efficient adsorption of CO and hydrogenation reactions. Thus, the energy barrier of the rate-determining step is reduced to enhance the electrocatalytic activity and stability. This study elucidates that the spatial structure of metal sites in HEOs is able to regulate CO adsorption status for eCORR, paving the way for the rational design of efficient HEO catalysts.