Polymer-Catalyst-Modified Cadmium Sulfide Photochemical Diodes in the Photolysis of Water

Surface modification of single-crystal CdS photochemical diodes with electrically conductive polypyrrole in combination with catalytic dispersions of transition metals (Pt, Rh, RuO₂) immobilized in polystyrene films has been shown to be effective in the stabilization of the semiconductor against degradation during the visible light-induced water-cleavage reaction. The weight ratio of metal-to-polystyrene affected the conductivity and electroactivity of the films. These factors and the hydrophobic nature of the polystyrene films were important in achieving high catalytic activity and stability of the CdS semiconductor. Sorption processes and the electronic contact between the polymer and the semiconductor also influenced the net yields of H₂ produced from water. Polystyrene-immobilized catalytic dispersions of Rh black were more effective for the production of H₂ from water than films containing Pt black or RuO₂ powder.