Defect-Driven Atomic Engineering: Oxygen Vacancy-Stabilized Co Single Atoms on Ordered Ultrathin TiO Nanowires for Efficient CO-to-Syngas Photoreduction.

Single-atom catalysts (SACs) anchored on defective supports offer exceptional catalytic efficiency but face challenges in stabilizing isolated metal atoms and optimizing metal-support interactions. Here, a defect-driven strategy is reported to construct a 3D dendritic SAC comprising interwoven ultrathin TiO nanowires (NWs) with abundant oxygen vacancies (OVs) that stabilize atomically dispersed cobalt (Co) sites. Using hydrothermal synthesis followed by acid etching and calcination, Ti─Co─Ti motifs are engineered at OVs site. The 3D architecture provides multiscale porosity and charge transport, achieving syngas production rates of 28.4 mmol g·h (CO) and 13.9 mmol g·h (H) with a high turnover frequency (TOF) of 10.6 min, surpassing many other state-of-the-art Co-based SACs. In situ Raman and electron paramagnetic resonance (EPR) analysis reveal OVs consumption during Co anchoring, while density functional theory (DFT) validates charge redistribution from Ti to Co, enabling efficient electron transfer and inducing strong electronic interactions that enhance CO adsorption and activation. The results highlight the interplay between atomic-scale coordination environments and macroscale architectural order in harnessing the catalytic potential of SACs and ultrathin 1D NWs.