Type-II Heterostructure Graphitic Carbon Nitride/Bismuth Molybdate Nanohybrid Materials for Photoelectrocatalytic
C. Murugan and A. Pandikumar
Electro Organic & Materials Electrochemistry Division, CSIR-Central Electrochemical Research Institute, Karaikudi-630 003, Tamil Nadu, India.
Academy of Scientific and Innovative Research (AcSIR), Ghaziabad- 201002, India
Abstract: Owing to care over environmental pollution and conservation of fossil fuels, the development of alternative systems for energy conservation have gained importance recently. Hydrogen is expected to play a vital role in the future as an efficient (high energy density-140 MJ/kg) and alternative to fuel fossils. The photoelectrocatalytic (PEC) water splitting is a promising avenue for sustainable hydrogen production by using metal oxide semiconductor. Recently, bismuth-based materials have more attention due to their narrow band gap, non-toxicity, low cost, and unique electronic structure with a well-dispersed valence band comprising Bi-6s and O-2p orbitals offer a suitable band gap to harvest visible light. Moreover, the bismuth-based metal oxides such as BiVO4, Bi2MoO6 and Bi2WO6 have high positive valance band potential than water oxidation potential that facilitate the water oxidation reaction. Even though bismuth-based metal oxides are promising photoanode, in practical the photo-efficiency is considerably low because of the poor photogenerated carrier’s separation, high bulk and surface recombination rates and slow water oxidation kinetics. Hence, great efforts have been made to improve the photocatalytic properties of bismuth-based metal oxides, e.g., developing heterojunctions/structures, tuning the morphologies, doping of metal and nanometals, and facet selective deposition. Out of these the formation of heterojunctions/structures with another semiconductor is efficient technique, in this method the charge carrier (electron/hole) moves to one semiconductor to another semiconductor, that leads to reduce the charge recombination and increase the interfacial charge transfer. In the present work, the Bi2MoO6 photoanode efficiency was enhanced by making heterostructure with graphitic carbon nitrite (g-C3N4), g-C3N4 is a metal free semiconductor with the band gap of 2.7 eV. The photoelectrocatalytic performance of the prepared materials towards water splitting was evaluated by using linear sweep voltammetry and chronoamperometry techniques under dark and illumination of AM 1.5G (100 mW cm-2) in 1 M KOH. The photocurrent density of the prepared g-C3N4/Bi2MoO6 nanohybrid is ~28 and ~7 fold greater than pristine Bi2MoO6 and g-C3N4, due to formation of type-II heterostructure, which leads to extremely large surface area provides more reaction sites, less recombination rate of photogenerated electron-hole pairs and rapid interfacial charge transfer.
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