Efficient electron extraction by CoS₂loaded onto anatase TiO₂for improved photocatalytic hydrogen evolution

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 O^2-anions forming CoOspecies 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.