Synergy of yolk-shelled structure and tunable oxygen defect over CdS/CdCO3-CoS2: Wide band-gap semiconductors assist in efficient visible-light-driven H2 production and CO2 reduction

• The yolk-shelled CoS 2 is successfully fabricated via self-sacrificing strategy. • Defect-riched CdS/CdCO 3 is firstly grown in-situ on CoS 2 via solubility product displacement method. • Introduction of wide-band CdCO 3 highly promotes H 2 evolution of CdS-CoS 2 . • Mie’s theory and monochromatic light HER indicates the possible Mie resonance. Yolk-shelled CoS 2 nanospheres are designed through Kirkendall Effect and subsequently converted into defect-rich CdS/CdCO 3 -CoS 2 photocatalysts via in-situ growth method. The optimal CdS/CdCO 3 -CoS 2 exhibits a significant hydrogen evolution rate of 64867.88 μmol h −1 g cat −1 that is 3.23 and 49.45 folds higher than CoS 2 -CdS and pure CdS. CO 2 reduction rate of CdS/CdCO 3 -CoS 2 is detected additionally (654.7 μmol h −1 g cat −1 ). Yolk-shelled CdS/CdCO 3 -CoS 2 induces the multi-scattering of incident light, possessing 1.52-fold H 2 production rate than that of full hollow ones. Enhanced photoexcited-carriers migration efficiency is attributed to the synergistic effect between possible Mie resonance at about λ = 450 nm in yolk-shelled architecture based on Mie’s theory and monochromatic light HER test, and the formation of defect energy level within the wide-band gap of CdCO 3 in Schottky-type/type II heterojunction. Electron paramagnetic resonance, positron annihilation spectroscopy and density functional theory calculation etc. are employed to validate the presence of oxygen vacancies and the photocatalytic mechanism.