Enhanced photocatalytic Hydrogen generation by splitting water using Sodium Alginate decorated rGO-CdS hybrid photo-catalyst

Abstract

A Spherical bead like hybrid photo-catalyst rGO-CdS-Sodium Alginate, comprising of water adsorbent Sodium Alginate, a visible light active semiconductor Cadmium Sulphide and an excellent electron transporter reduced graphene oxide, is hydrothermally synthesized, characterised and tested for hydrogen generation from water in presence of visible light (45 W LED). Sodium Alginate, a biopolymer, with very good moisture adsorbing capacity due to the presence of functional groups like hydroxyl and carboxyl, was used to fabricate spherical beads, which adsorbed and stored the water molecule by intermolecular hydrogen bonding with the functional groups. Instead of the conventionally used powder photo-catalyst, spherical beads make the continuous operation of the photo-reactor easier. The toxic and photo-corrosive effects of CdS were minimized in this process through the encapsulation by rGO-Sodium Alginate. Reduced Graphene Oxide (rGO), an electron transporter, aided in decreasing the recombination rate of photo-generated electron-hole pairs. SEM analysis confirms nano-fibrils of Sodium Alginate interspersed with nano-flowers of CdS on the crumpled up sheets of Graphene. The hybrid photocatalyst exhibits a lower band gap (2.33 eV) compared to pristine CdS (2.4 eV). The maximum value of the photocatalytic activity of 6 mmol h−1 g−1 is achieved using the hybrid photo-catalyst with the optimum loading, in absence of any co-catalyst. This rationally designed composite photo-catalyst will bring new insight into the field of photocatalytic water splitting.