Synthesis of g‐C 3 N 4 /ZnGa 1.9 Al 0.1 O 4 Heterojunction Using Narrow and Wide Band Gap Material for Enhanced Photoelectrochemical Water Splitting

We fabricated visible‐light responsive g‐C 3 N 4 /ZnGa 1.9 Al 0.1 O 4 heterojunction nanocomposites using narrow band gap g‐C 3 N 4 and wide band gap mesoporous ZnGa 1.9 Al 0.1 O 4 by thermolysis and hydrothermal methods. The charge‐transfer, electrons‐holes separation and its kinetics across the intimate interface of g‐C 3 N 4 /ZnGa 1.9 Al 0.1 O 4 were systematically investigated using photoelectrochemical (PEC) measurements. The high‐resolution transmission electron microscopy (HR‐TEM) shows an intimate interface between g‐C 3 N 4 and ZnGa 1.9 Al 0.1 O 4 nanocrystals in the heterojunctions. The PEC measurements revealed higher photocurrent density towards water splitting in case of heterojunction prepared by thermolysis method compared to hydrothermal process without noble metal co‐catalyst with excellent stability. The remarkable water splitting activity is mainly ascribed to the least recombination rate of electrons and holes, facile kinetics and least charge‐transfer resistance. This is further confirmed by kinetic studies using Tafel slope and exchange‐current density data.