Photochemical Deposition of Pt on CdS for H2 Evolution from Water: Markedly Enhanced Activity by Controlling Pt Reduction Environment

Abstract

Pt is one of the most effective cocatalysts used in hydrogen evolution photocatalysts in water splitting. However, because Pt is an expensive noble metal, the efficient and optimum use of Pt is of high importance. In this work, the effect of loading conditions for Pt nanoparticles on the surface of CdS as a model photoabsorber was studied to reveal the important parameters for obtaining Pt cocatalyst of high activity. The activities of as-prepared Pt/CdS samples were evaluated in H2 evolution from photocatalytic water splitting using Na2S and Na2SO3 as sacrificial reagents. It was found that the solution environment during Pt photoreduction played a critical role. Pt/CdS photocatalyst with Pt reduced in NaOH alkaline solution exhibited a markedly higher H2 evolution activity (∼1300 μmol h–1) than samples obtained in acidic or neutral solution (<50 μmol h–1). Further materials characterization revealed that, in alkaline solution, Pt4+ species in the precursor (H2PtCl6·xH2O) can be well reduced to metallic ...