Hydride Vacancy−Driven Photothermal C−H Activation over Ni/TiH ₂ Catalysts

Dry reforming of methane (DRM) offers a route for utilizing CH4 and CO2; its application remains limited by the high temperatures (>700°C) required to overcome the kinetic barriers of C−H bond activation. Herein, we report a photothermal Ni/TiH2 catalyst that enables highly efficient DRM conversion below 450 °C. Surface hydride vacancies in TiH2 as the active sites for direct C−H activation of CH4 under photothermal conditions, while its lattice hydrogen dynamically replenishes these vacancies to sustain a high density of reactive sites. Isotope labeling experiments confirmed that the Ni nanoparticles as the primary centers for H−D bond dynamic exchange reactions (H2 formation), effectively coupling vacancy-driven methane activation with CO2 dissociation. The kinetic and theoretical studies revealed that photogenerated charge carriers promote the formation and stabilization of surface hydride vacancies and accelerate subsequent surface reaction steps. As a result, a CO production rate of 545.4 mmol·gNi−1·h−1 is achieved at 200 °C, exceeding the thermodynamic equilibrium limit over three orders of magnitude and delivering a light-to-fuel efficiency of approximately 8.0%. These findings elucidate the mechanistic role of surface hydride vacancy in C−H activation and highlight the potential of metal hydrides as promising supports for CH4 and CO2 conversion.