Amorphization‐Induced <i>d</i>‐Orbital Rearrangement in Ultrathin CoO Nanosheets with Strong <i>d</i>‐<i>p</i> Interactions for Efficient CO₂ Photoreduction

Abstract

AbstractPhotocatalytic CO2 conversion into syngas presents a sustainable avenue for mitigating carbon emissions while generating value‐added fuels. However, sluggish charge carrier dynamics and weak, non‐specific interactions between catalytic sites and CO2 molecules limit efficiency. Herein, ultrathin amorphous CoO nanosheets (a‐CoO) are reported that integrate structural and electronic advantages for enhanced CO₂ photoreduction. X‐ray absorption spectroscopy and density functional theory analyses reveal that amorphization partially transforms the local crystal field of Co from quasi‐octahedral to quasi‐tetrahedral coordination, resulting in a greater population of unpaired electrons in the frontier d‐orbitals. This reconfiguration promotes electron injection from Co 3dyz into the 2π* antibonding orbitals component of C 2px in CO2, which strengthens 3d‐2p orbital hybridization and lowers the activation energy barrier. In situ spectroscopic further confirms that this orbital restructuring accelerates charge transfer from the Co center to CO2 and facilitates its activation. Meanwhile, the ultrathin 2D architecture improves the separation and transport of photoexcited carriers. Consequently, vigorous bubbles are observed under visible light irradiation, with a total syngas evolution rate of 23.7 mmol g−1 h−1 (12.6 and 11.1 mmol g−1 h−1 for CO and H2, respectively) and an apparent quantum efficiency of 1.28% at 450 nm—≈8.7‐fold improvement over its crystalline counterpart.