Noble-Metal-Free High-Entropy Alloy Nanoparticles for Efficient Solar-Driven Photocatalytic CO₂ Reduction

Metal nanoparticle (NP) cocatalysts are widely investigated for their ability to enhance the performance of photocatalytic materials; however, their practical application is often limited by the inherent instability under light irradiation. This challenge has catalyzed interest in exploring high-entropy alloys (HEAs), which, with their increased entropy and lower Gibbs free energy, provide superior stability. In this study, 3.5 nm-sized noble-metal-free NPs composed of a FeCoNiCuMn HEA are successfully synthesized. With theoretic calculation and experiments, the electronic structure of HEA in augmenting the catalytic CO₂ reduction has been uncovered, including the individual roles of each element and the collective synergistic effects. Then, their photocatalytic CO₂ reduction capabilities are investigated when immobilized on TiO₂. HEA NPs significantly enhance the CO₂ photoreduction, achieving a 23-fold increase over pristine TiO₂, with CO and CH₄ production rates of 235.2 and 19.9 µmol g^-1 h^-1, respectively. Meanwhile, HEA NPs show excellent stability under simulated solar irradiation, as well high-energy X-ray irradiation. This research emphasizes the promising role of HEA NPs, composed of earth-abundant elements, in revolutionizing the field of photocatalysis.