Titanium dioxide (TiO2) as a benchmark photocatalyst has been attracting attention due to its photocatalytic activity combined with photochemical stability. In particular, TiO2with anatase polymorph holds promise for driving reduction reactions, such as proton reduction to evolve H2via photocatalysis. In this study, anatase TiO2is loaded with CoS2through the hydrothermal route to form a CoS2@TiO2photocatalyst system. X-ray absorption near edge structure confirms the +2-oxidation state of the Co cation, while extended x-ray absorption fine structure shows that each Co2+cation is primarily coordinated to six S-anions forming a CoS2-like species. A small fraction of the Co2+species is also coordinated to O2-anions forming CoxOyspecies and substitutionally resides at the Ti4+-sites. Further investigations with steady-state IR absorption induced by UV-light and time-resolved microwave conductivity suggest an efficient electron transfer from the conduction band of TiO2to the surface-loaded CoS2which acts as a metallic material with no bandgap. The CoS2shallowly traps electrons at the host surface and facilitates proton reduction. An appreciably enhanced H2evolution rate (8 times) is recognised upon the CoS2loading. The CoS2is here proposed to function as a proton reduction cocatalyst, which can potentially be an alternative to noble metals.
Keywords: cocatalyst; electron lifetime; electron population; hydrogen production; photocatalyst.
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