g-C3N4: Sn - doped In2O3 (ITO) nanocomposite for photoelectrochemical reduction of water using solar light

Abstract Graphitic carbon nitride (g-C3N4) nanosheets are well studied for photocatalytic water splitting using solar light. However, its photocatalytic activity is restrained due to fast recombination of photo-generated electron-hole pairs. Here, we introduce Sn-doped In2O3 (ITO) nanocrystals (NCs) as co-catalysts with g-C3N4 nanosheets, forming g-C3N4:ITO (2 wt%) nanocomposites, for photoelectrochemical (PEC) reduction of water to H2. The co-catalyst has two major impacts: (i) enhances charge transfer from g-C3N4 to ITO NCs suppressing the recombination of photoexcited electron-hole pair, and (ii) reduces charge transfer resistance at electrode/electrolyte interface. Both these aspects improve PEC activity of the nanocomposites. Our g-C3N4:ITO nanocomposites photoelectrode shows a photocurrent density of -70 μA/cm2 for reduction of water to H2, whereas the pristine g-C3N4 nanosheet photoelectrode shows -12 μA/cm2 photocurrent density at 0.11 V versus reversible hydrogen electrode (RHE). This (∼6 times) enhancement in photocurrent density by ITO NCs co-catalyst is reasonably high compared to other co-catalysts for g-C3N4 reported in prior literature.