CdS–AgGaS2 photocatalytic diodes for hydrogen production from aqueous Na2S/Na2SO3 electrolyte solution under visible light (λ ≥ 420 nm)

A p-type semiconductor, bulky AgGaS2, was prepared by the conventional solid state reaction and heat-treated at various temperatures under He and H2S gas flow to eliminate vacancies or interstitial defects and to improve the crystallinity. A p–n diode, n-CdS/p-AgGaS2 was fabricated by decorating AgGaS2 surface with nanoparticles of n-type CdS by the hydrothermal treatment. The configuration was confirmed by XRD, UV–vis spectroscopy and TEM. The composite photocatalyst of this new configuration exhibited a high rate of hydrogen production under visible light irradiation (λ ≥ 420 nm) from water containing sulfide and sulfite as hole scavengers. The photocatalytic diode system formed with n- and p-type semiconductors results in efficient charge separation, caused by the rectification of photo-electrons and holes generated upon photo-absorption.