A Review of Synthesis Techniques for Gallium-Zinc Oxynitride Solar-Activated Photocatalyst for Water Splitting

Abstract

Converting a practically limitless energy source, such as sunlight, into chemical energy with very little or no carbon footprint will pose a major challenge in the coming decades. The technology exists to convert solar energy into chemical fuels, such as hydrogen, through overall water splitting to produce hydrogen and oxygen. However, the photocatalytic efficiency is still below the feasibility limit. Many photocatalyst materials have been developed for solar hydrogen generation through water splitting in the last four decades. Gallium-zinc oxynitride (GaN:ZnO) solid solution is reported to be a suitable photocatalyst for overall water splitting and to have the highest photocatalytic activity. The traditional synthesis method contains difficulties and inefficiencies, such as long nitridation of starting materials at high temperatures and low Zn content of the synthesized photocatalyst. A number of experiments have been conducted in recent years to develop new synthesis approaches. In this article, a comprehensive review of various synthesis techniques of GaN:ZnO solid solution, along with their advantages and disadvantages, are presented. This information is essential for improving the efficiency of the synthesis techniques of GaN:ZnO solid solution and its photocatalytic activity for overall water splitting.

Graphene-wrapped hierarchical TiO2 nanoflower composites with enhanced photocatalytic performance

“…For example, in the case of photocatalytic water splitting, the photocatalyst must straddle both the H + /H2 reduction potential (0 eV vs. SHE) and the H2O/O2 oxidation potential (1.23 eV vs. SHE). 16 Based on heterostructuring a large band gap material with a small band gap material to create a wider absorption spectrum.…”

Facile one-step process for synthesis of vertically aligned cobalt oxide doped TiO2 nanotube arrays for solar energy conversion

“…Irradiation with energy equal to or higher than that of the photocatalyst band gap leads to generation of electrons and holes in the conduction band and valence band, respectively [7][8][9]. Holes oxidize H 2 O to produce O 2 at the photoanode and electrons reduce H + to H 2 at Pt electrode.…”

Size dependence of photocatalytic oxidation reactions of Rh nanoparticles dispersed on (Ga1-xZnx)(N1-xOx) support

“…This limits the visible-light absorption of the prepared solids. Consistent with this, an increase in the Zn content of the crystalline structure results in a shift of the absorption edge to higher wavelengths [15][16][17][18]. Han et al [16] used a sol-gel method to synthesize (Ga1-xZnx)(N1-xOx) (x = 0.482) with the absorption edge at 560 nm.…”