Graphene-Based Materials as Efficient Photocatalysts for Water Splitting

Abstract

Photocatalysis has been proposed as one of the most promising approaches for solar fuel production. Among the photocatalysts studied for water splitting, graphene and related materials have recently emerged as attractive candidates due to their striking properties and sustainable production when obtained from biomass wastes. In most of the cases reported so far, graphene has been typically used as additive to enhance its photocatalytic activity of semiconductor materials as consequence of the improved charge separation and visible light harvesting. However, graphene-based materials have demonstrated also intrinsic photocatalytic activity towards solar fuels production, and more specifically for water splitting. The photocatalytic activity of graphene derives from defects generated during synthesis or their introduction through post-synthetic treatments. In this short review, we aim to summarize the most representative examples of graphene based photocatalysts and the different approaches carried out in order to improve the photocatalytic activity towards water splitting. It will be presented that the introduction of defects in the graphenic lattice as well as the incorporation of small amounts of metal or metal oxide nanoparticles on the graphene surface improve the photocatalytic activity of graphene. What is more, a simple one-step preparation method has demonstrated to provide crystal orientation to the nanoparticles strongly grafted on graphene resulting in remarkable photocatalytic properties. These two features, crystal orientation and strong grafting, have been identified as a general methodology to further enhance the photocatalytic activity in graphenebased materials for water splitting. Finally, future prospects in this filed will be also commented.

Hydrogen production and photocatalytic activity of g‐C3N4/Co‐MOF (ZIF‐67) nanocomposite under visible light irradiation

“…Photocatalytic technology has been studied extensively in recent years to crack the energy crises and control ecological pollution . In this method, electrons (e − ) and holes (h + ) are generated from semiconductor materials under light irradiation and contribute to oxidation–reduction reactions, respectively . Pristine (single) materials suffer from rapid charge recombination, based on this reason researchers developed multi‐components photocatalysts comprising of semiconductor composites, in which the produced heterojunctions can encourage the charge separation one compound to another compound and improve the photocatalytic dye degradation, CO 2 reduction and hydrogen production activity …”

“…[1] In this method, electrons (e − ) and holes (h + ) are generated from semiconductor materials under light irradiation and contribute to oxidation-reduction reactions, respectively. [2] Pristine (single) materials suffer from rapid charge recombination, based on this reason researchers developed multi-components photocatalysts comprising of semiconductor composites, in which the produced heterojunctions can encourage the charge separation one compound to another compound [3] and improve the photocatalytic dye degradation, [4] CO 2 reduction [5] and hydrogen production activity. [6] Metal-organic frameworks (MOF) are a novel class of porous material, which are constructed from metal ions (M + )/clusters linked by organic ligands to form 1D, 2D, or 3D structures.…”

Photosensitive Hybrid Nanostructured Materials: The Big Challenges for Sunlight Capture

“…In the last years, carbon-based nanostructured materials, such as graphene and its derivatives [155,156], fullerenes, activated carbons [26,157], biochar [158,159], carbon nanotubes (CNTs) [13,160], and nanoparticles [161], have been of great interest because of their unique structural, electrical, and mechanical properties, offering promising opportunities for photocatalytic applications (Figure 7).…”

Dye‐Sensitized Heterogeneous Photocatalysts for Green Redox Reactions

“…(i) photo‐induced charge generation, (ii) charge migration, (iii) photochemical reactions and (iv) charge recombination. Reproduced from ref . under the Creative Commons Attribution (CC BY) license.…”