Enhanced charge transfer in surface-modified NiTiO3 using high-entropy oxide nanoparticles for solar-driven methanol production

The photocatalytic reduction of CO 2 into solar fuels for harnessing solar energy was achieved through the synthesis of a heterostructure comprising a high-entropy oxide (HEO) of (CoCrFeNi)O x and NiTiO 3 nanorods (NTO) prepared by an ammonia evaporation technique. The HEO/NTO heterostructure demonstrated outstanding efficiency in photocatalytic CO 2 reduction, as the incorporation of HEO into NTO generated intrinsic electric fields that significantly enhanced charge transfer and suppressed charge carrier recombination. X-ray photoelectron spectroscopy confirmed that HEO acts as a photogenerated electron donor within the HEO/NTO heterostructure. Furthermore, in-situ diffuse reflectance infrared Fourier transform spectroscopy verified the formation of *CH 3 O and *COOH intermediates, which helped elucidate the kinetic characteristics of the reaction pathway involved in the conversion of CO 2 to CH 3 OH. The optimized HEO/NTO heterojunction exhibited superior photocatalytic CO 2 reduction activity, achieving a methanol production rate of 618 μmol g –1 h –1 , which is 9.6 times higher than that of pure NTO. The remarkable enhancement in CO 2 reduction was primarily attributed to the efficient transport of photoexcited electrons and holes facilitated by the HEO/NTO heterostructure, as demonstrated by photoluminescence spectra, electrochemical impedance spectroscopy, and transient photocurrent response analyses. Overall, this study presents a promising strategy for the rational design of high-performance heterostructures to improve the transport, separation, and utilization of light-induced charge carriers. • (CoCrFeNi)O x /NiTiO 3 fabricated by incorporating (CoCrFeNi)O x NiTiO 3 nanorods via ammonia evaporation method. • Time resolved photoluminescence confirms fast charge transfer in (CoCrFeNi)O x /NiTiO 3 following an S-scheme mechanism. • Methanol production over 40-(CoCrFeNi)O x /NiTiO 3 was enhanced 9.6 folds great than of NiTiO 3 achieving an AQE of 8.4 %. • DRIFTS explores the reaction mechanism and CO 2 interaction with (CoCrFeNi)O x /NiTiO 3 during photocatalytic CO 2 reduction.