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

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.