Effect of palladium chemical states on CO2 photocatalytic reduction over g-C3N4: Distinct role of single-atomic state in boosting CH4 production

Cocatalyst decoration has been recognized as an effective strategy in photocatalysis, yet the critical role of sing-atomic state on CO2 photocatalytic reduction, distinguished from oxide and elemental states, remains a mystery hitherto. Herein, single-atom Pd (Pd-SA), oxides (PdOx), nanoparticles (Pd-NP), were homogeneously anchored g-C3N4 (CN) to investigate their reduction behaviors under visible-light irradiation. Performance tests showed species improved CH4 production CN, with Pd/CN-SA exhibiting optimum yields (2.25 μmol g–1), markedly higher than that PdOx/CN (1.08 g–1) Pd/CN-NP (0.44 g–1). After comprehensive mechanism analysis various characterization techniques, in-situ DRIFT spectra DFT calculations, it was found conducive activation CO2, negative conduction band potentials, excellent •H utilization efficiency, collaboratively contributed superior Pd/CN-SA. Despite larger electron density PdOx/CN, moderate ability photogenerated electrons restricted further adsorbed CO intermediate, limiting enhancement activity. Furthermore, evolutions also limited by poor supply inferior respectively. It is expected effect chemical especially single-atomic state, revealed this work can inspire rational design more advanced photocatalysts for reduction.