2D Nanocomposite of g-C₃N₄ and TiN Embedded N-Doped Graphene for Photoelectrochemical Reduction of Water Using Sunlight

Photoelectrochemical (PEC) water splitting is a sustainable pathway for solar to hydrogen conversion. Graphitic carbon nitride (g-C₃N₄) nanosheets have the suitable bandgap and band-edge energies to act as a visible-light photocatalyst for water splitting, but the fast recombination of photoexcited electron–hole pair limits the efficiency. Herein, N-doped few-layer graphene (NFG) dressed with titanium nitride (TiN) nanocrystals (TiN-NFG) is introduced as an efficient co-catalyst which improved the water reduction activity of g-C₃N₄ by 16 times. The 2D nanocomposite of g-C₃N₄:TiN-NFG has an extended interface for efficient separation of photoexcited electron–hole pair through electron transfer from g-C₃N₄ to TiN-NFG. The metal-like electronic structure of TiN in combination with good charge conducting capability of NFG reduces the charge transfer resistance at the electrode/electrolyte interface. Both these aspects are responsible for the enhanced PEC activity leading to a photocurrent density of −196 µA cm⁻² at 0.11 V versus reversible hydrogen electrode as a photocathode for the g-C₃N₄:TiN-NFG nanocomposite. The nanocomposite is stable, low cost (free from noble metals), and the extent of enhancement in the PEC efficiency for reduction reaction is remarkable compared to prior literature.