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Unique Features of the Photocatalytic Reduction of H2O and CO2 by New Catalysts Based on the Analogues of CdS, Cd4P2X3 (X = Cl, Br, I)

Roy, Anand, Chhetri, Manjeet, Prasad, Suchitra, Waghmare, Umesh V., Rao, C. N. R.
ACS applied materials & interfaces 2018 v.10 no.3 pp. 2526-2536
bromine, carbon dioxide, carbon monoxide, chlorine, electrochemistry, hydrogen, hydrogen production, ions, irradiation, materials science, methane, photocatalysis, photocatalysts, solar radiation, spectral analysis, sulfides
Photochemical reduction of H₂O and CO₂ has been investigated with a new family of catalysts of the formula Cd₄P₂X₃ (X= Cl, Br, I), obtained by the complete aliovalent substitution of the sulfide ions in CdS by P and X (Cl, Br, I). Unlike CdS, the Cd₄P₂X₃ compounds exhibit hydrogen evolution and CO₂ reduction from water even in the absence of a sacrificial agent or a cocatalyst. Use of NiₓPy as the cocatalyst, enhances hydrogen evolution, reaching 3870 (apparent quantum yield (AQY) = 4.11) and 9258 (AQY = 9.83) μmol h–¹ g–¹, respectively, under artificial and natural (sunlight) irradiation, in the case of Cd₄P₂Br₃/NiₓPy. Electrochemical and spectroscopic studies have been employed to understand the photocatalytic activity of this family of compounds. Unlike most of the semiconductor-based photocatalysts, Cd₄P₂X₃ catalysts reduce CO₂ to CO and CH₄ in the absence of sacrificial-agent or cocatalyst using water as the electron source. CO, CH₄, and H₂ have been obtained with these catalysts under artificial as well as sun-light irradiation. First-principles, calculations have been carried out to understand the electronic structure and catalytic features of these new catalysts.