High-Entropy Oxides: A New Frontier in Photocatalytic CO₂ Hydrogenation

Herein, we investigate the potential of nanostructured high-entropy oxides (HEOs) for photocatalytic CO₂ hydrogenation, a process with significant implications for environmental sustainability and energy production. Several cerium-oxide-based rare-earth HEOs with fluorite structures were prepared for UV-light driven photocatalytic CO₂ hydrogenation toward valuable fuels and petrochemical precursors. The cationic composition profoundly influences the selectivity and activity of the HEOs, where the Ce_0.2Zr_0.2La_0.2Nd_0.2Sm_0.2O_2-δ catalyst showed outstanding CO₂ activation (14.4 mol_CO kg_cat^-1 h^-1 and 1.27 $$ kg_cat^-1 h^-1) and high methanol and CO selectivity (7.84% CH₃OH and 89.26% CO) under ambient conditions with 4 times better performance in comparison to pristine CeO₂. Systematic tests showed the effect of a high-entropy system compared to midentropy oxides. XPS, in situ DRIFTS, as well as DFT calculation elucidate the synergistic impact of Ce, Zr, La, Nd, and Sm, resulting in an optimal Ce³⁺/Ce⁴⁺ ratio. The observed formate-routed mechanism and a surface with high affinity to CO₂ reduction offer insights into the photocatalytic enhancement. While our findings lay a solid foundation, further research is needed to optimize these catalysts and expand their applications.