Solvent‐Assisted Synthesis of Supramolecular‐Assembled Graphitic Carbon Nitride for Visible Light Induced Hydrogen Evolution – A Review

Abstract

Many graphitic carbon nitride (g‐C3N4)‐based photocatalysts have attracted a significant interest because of the unique arrangement of carbon and nitrogen atoms. Changeable morphologies with tunable bandgap of g‐C3N4 materials were used in many applications including batteries, photovoltaics, photocatalysts, sensors, etc. This review focuses on the recent progress in the solvent assisted supramolecular‐assembled carbon nitride preparation for visible light induced hydrogen evolution from water. The synthesis involves tailoring the supramolecular assembly from different monomers followed by calcination. Different types of non‐covalent interactions between the monomers have been explained. In addition, the crucial role of solvent has been re‐counted in terms of the alteration of the structural morphology of assemblies. The mechanistic pathways of interaction in the formation of supramolecular assemblies have been also documented by molecular dynamics simulation. Finally, visible light triggered hydrogen evolution has been demonstrated along with discussion on challenges and future research direction.

Non-Metal-Doped Porous Carbon Nitride Nanostructures for Photocatalytic Green Hydrogen Production

“…Photovoltaic electrolysis-driven H 2 production, especially for automobile applications, is not feasible supposing the fueling station needs nearly 1000 kg H 2 /day and considering that the minimal electrical energy required for production of 1kg H 2 is 51 kWh (utilizing an electrolyzer efficiency of 65%) [ 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 ]. Thereby, 1000 kg H 2 /day needs 51,000 kWh/day of electricity that requires operation of 10,200 kWp or 10.2 megawatts of PV power.…”

“…Direct solar H 2 O splitting entails the direct utilization of solar energy in the production of H 2 from water without going through intermediate electrolysis, which includes the following concepts [ 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 ]: Photoelectrochemical H 2 O splitting driven by quantum dots or semiconductor (i.e., electrodes using a photoelectrochemical cell) to convert light energy into H 2 chemical energy. Photoelectrochemical systems could be based on semiconductors or dyes and using dissolved metal complexes.…”

“…In particular, considering daily sunlight illumination (AM 1.5 G) of 7.6 h (assigned to 240 W/m 2 ), to reach a hydrogen price of 3.5 USD/kg, it is estimated that a HER system with an STH of (10%), lifetime of (10 years), decreasing rate of 4%/year, and subsequent acceptable cost of 102 USD/m 2 is required. Therefore, further efforts including both experimental and theoretical studies along with fundamental investigations are needed to develop efficient and low-cost photocatalysts for large-scale photocatalytic HER processes [ 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 ].…”

“…Porous gCNs are semiconductors with a bandgap of nearly 2.7 eV and high adsorption of blue-violet light with a wavelength of (<475 nm) that accelerate the migration of photogenerated electrons along with delayed electron–hole recombination [ 26 , 27 , 28 , 29 , 30 , 31 ]. Moreover, porous gCNs possess high surface area, low density, rich electron density, and massive active sites, which can accelerate the reaction kinetics and maximize the utilization of elements during HER [ 33 , 34 , 35 ]. The physiochemical and photocatalytic properties of gCNs are easily modulated via the incorporation of metal or non-metal elements to form various heterojunction structures of Z-Scheme, Type-II, and S-Scheme [ 33 , 34 , 35 , 36 , 37 ].…”

“…Moreover, porous gCNs possess high surface area, low density, rich electron density, and massive active sites, which can accelerate the reaction kinetics and maximize the utilization of elements during HER [ 33 , 34 , 35 ]. The physiochemical and photocatalytic properties of gCNs are easily modulated via the incorporation of metal or non-metal elements to form various heterojunction structures of Z-Scheme, Type-II, and S-Scheme [ 33 , 34 , 35 , 36 , 37 ]. Heteroatoms (i.e., B, S, O, F, and P) are easily integrated into the skeleton structure of gCNs to optimize their electronic structure, bandgap energy, visible-light absorption, and photocatalytic properties [ 35 , 38 , 39 ].…”