《Appl. Catal. B-Environ.》: Complete Selectivity Switching between CO and CH₄ for CO₂ Photoreduction on Pd-SrTiO₃

Suning Zhang,+ Jinyu Ding,+ Peijin Du,+ Feng Chen, Jun Hu, Qingxia Chen, Xia Wang, Xiaodong Li, and Xingchen Jiao*

Carbon dioxide (CO₂) photoreduction to methane (CH₄) encounter low selectivity. This is mainly attributed to insufficient protons to sustain deep protonation; additionally, linearly adsorbed intermediates on single active sites tend to undergo direct desorption to form carbon monoxide (CO). Herein, we designed Pd nanoparticle-loaded semiconductor oxides nanocrystals, in which Pd not only facilitates water dissociation to generate protons, but also enables the construction of interfacial dual sites for bridge-mode adsorption of reaction intermediates. As a prototype, Pd nanoparticle-loaded SrTiO₃ nanocrystals were synthesized. Density functional theory calculations indicate Sr–Pd hetero-sites stabilize *COOH and enhance *CO adsorption; Pd incorporation lowers the water dissociation barrier from 0.97 to 0.79 eV and facilitates sustained hydrogen spillover to generate sufficient active H species. Quasi in situ X-ray photoelectron spectroscopy and charge density difference results confirm the charge redistribution and forms electron-rich dual-active sites. Hence, the Pd-SrTiO₃ nanocrystals achieved nearly 100% selectivity toward CH₄, whereas the SrTiO₃ nanocrystals only produced CO. This work establishes a rational principle for designing high-selectivity photocatalysts toward deep CO₂ conversion into CH₄.