Role of Graphene in Photocatalytic Solar Fuel Generation

Abstract

One of the most promising methods for conversion and storage of solar energy is in the form of the chemical bonds of an energy carrier, such as hydrogen or light hydrocarbons. However, the traditional methods to harness and store solar energy are simply too expensive to be implemented on a large scale. It has been documented that the recombination of photo-induced charge carriers is the greatest source of inefficiency in photocatalytic systems. In the last decade, graphene derivatives and their functionalized nanostructures were extensively utilized for various roles to improve the efficiency of photocatalytic solar fuel generation. These include photocatalyst/redox active sites via band gap and defect density engineering, charge acceptor due to their excellent carrier mobility, a solid-state charge mediator by electronic band alignment, and light absorber by taking advantage of their photoluminescence characteristics at the nanoscale. This chapter aims to provide an authoritative and in-depth review on the properties and application of graphene derivatives, as well as the recent advances in the design of graphene-based photocatalytic systems. The knowledge extracted from the presented materials can be applied to other applications dealing with surface chemistry, interfacial science, and optoelectronic device fabrication.

Enhanced Gas Sensing Performance of Photo-Activated, Pt-Decorated, Single-Crystal ZnO Nanowires

“…Thus, Pt deposition increases the oxygen ions' surface occupancy and results in the rapid injection of photo-excited charges to surface active sites with larger working functions and the subsequent reduction of favorable catalytic facets. 37 The I-V characteristics of gas sensors are known to be a promising representative of electron density and oxygen vacant defects of nanostructures. 36 As illustrated in Figure 6b, the electrical current proportionally increases with Pt concentration in the samples, thus confirming the higher number of oxygen vacant sites.…”

Photocatalytic Production of Oxygen by Nitrogen Doped Graphene Oxide Nanospheres: Synthesized via Bottom‐Up Approach Using Dibenzopyrrole

“…These reports highlighted the effects of quantum confinement to band gap. For nano‐sized graphene, a band gap as low as 0.5 eV has been predicted [13–14] . Furthermore, topological, edge, or elemental defects affect the spin densities and polarizability of nano graphene.…”

“…By adjusting the ratio of the sp 2 and sp 3 fractions via oxidation/reduction chemistry, one can change the GO into a semiconductor or graphene-like semi-metal. [8][9][10][11][12][13][14] Graphene semiconducting molecules have several advantages over metal-assisted photocatalysts, including low cost, ease of production, and compatibility with a variety of substrates. [8][9] The suitable band gap for driving visible light photocatalysis is between 2 to 3 eV.…”

“…For nano-sized graphene, a band gap as low as 0.5 eV has been predicted. [13][14] Furthermore, topological, edge, or elemental defects affect the spin densities and polarizability of nano graphene. These also have an impact on the specificity of the reaction.…”

“…A 2D network of sp 2 and sp 3 bonded atoms is produced in GO by the oxygenated functional groups, which results in the presence of a finite bandgap that depends on isolated sp 2 domains. By adjusting the ratio of the sp 2 and sp 3 fractions via oxidation/reduction chemistry, one can change the GO into a semiconductor or graphene‐like semi‐metal [8–14] . Graphene semiconducting molecules have several advantages over metal‐assisted photocatalysts, including low cost, ease of production, and compatibility with a variety of substrates [8–9] …”