Recent Progress in Multifunctional Graphene-Based Nanocomposites for Photocatalysis and Electrocatalysis Application

Abstract

The global energy shortage and environmental degradation are two major issues of concern in today's society. The production of renewable energy and the treatment of pollutants are currently the mainstream research directions in the field of photocatalysis. In addition, over the last decade or so, graphene (GR) has been widely used in photocatalysis due to its unique physical and chemical properties, such as its large light-absorption range, high adsorption capacity, large specific surface area, and excellent electronic conductivity. Here, we first introduce the unique properties of graphene, such as its high specific surface area, chemical stability, etc. Then, the basic principles of photocatalytic hydrolysis, pollutant degradation, and the photocatalytic reduction of CO₂ are summarized. We then give an overview of the optimization strategies for graphene-based photocatalysis and the latest advances in its application. Finally, we present challenges and perspectives for graphene-based applications in this field in light of recent developments.

Keywords: CO2 fixation; electrocatalysis; graphene composites; photocatalysis; pollutant degradation.

Figure 1

Semiconductor−based photocatalysis perspective. Reprinted with permission from Ref. [93]. Copyright©2018 Production and hosting by Elsevier B.V. on behalf of King Saud University.

Figure 2

The photocatalytic performance of CO₂ reduction, optical and photoelectrical properties, and mechanism of the charge transfer pathway. Time-dependent production of (a) CH₄ and (b) CO in photocatalytic CO₂ reduction with different catalysts under visible light (λ ≥ 420 nm). The photocatalytic reactions were carried out in a batch system under standard atmospheric pressure. The partial pressure of CO₂ and H₂O were constant, with the water content below the scaffold-loading photocatalyst. Under visible-light irradiation, the temperature of the water was measured to be about 50 °C. (c) Average efficiency of photocatalytic CO₂ conversion with different catalysts during 5 h of visible-light (λ ≥ 420 nm) irradiation. (d) UV–Vis absorption spectra of TiO₂, TiO₂-G, and HCP–TiO₂-FG catalysts. (e) Amperometric I−t curves of samples under visible-light (λ ≥ 420 nm) irradiation. (f) Proposed mechanism of charge separation and transfer within the HCP–TiO₂-FG composite photocatalyst under visible-light (λ ≥ 420 nm) irradiation. Reprinted with permission from Ref. [135]. Copyright©2023 Springer Nature Limited.

Figure 3

(a) Calculated mechanism with the molecular unit of Co−based metal−organic frameworks (MOFs) for photocatalytic CO₂−to−CO conversion, showing the calculated redox potentials and free energy changes. (b) Proposed photocatalytic mechanism. Reprinted with permission from Ref. [145]. Copyright©2023 Springer Nature Limited.

Figure 4

Illustration of energy level diagram and simplified structure of (a) coal GQD, GQD−OPD (o−phenylenediamine), GQD−DNPT23, GQD−DNPT18, and GQD−BNPTL and (b) coal GQD, GQD−Anln−OCH₃, GQD−Anln−OCF₃, and GQD−Anln−OCCl₃. The Fermi levels for p-type conductivity (E_Fp) and n−type conductivity (E_Fn) are indicated in the energy diagram. Reprinted with permission from Ref. [146]. Copyright©2023 American Chemical Society.

Figure 5

UV–Vis absorbance spectra (a) and accordingly obtained plots (b) of (αE)2 versus photon energy (E) (where α denotes the absorbance coefficient) of coal GQD, GQD-OPD, GQD-DNPT23, GQD-DNPT18, and GQD-BNPTL. The horizontal intercept of the tangent line in (b) indicates the bandgap of each GQD type. (c) Cathodic linear sweep voltammetry (c) and anodic linear sweep voltammetry (d) of coal GQD, GQD-OPD, GQD-DNPT23, GQD-DNPT18, and GQD-BNPTL. The horizontal intercept of the tangent line in (c) or (d) determines the conduction band minimum (CBM) or the valence band maximum (VBM) of each GQD type, respectively. Reprinted with permission from Ref. [146].Copyright©2023 American Chemical Society.

Figure 6

(a) Schematic diagram of the co−doped np-graphene−based all−solid-state Zn−air battery. (b) Polarization and power density curves of the batteries. (c) Discharge/charge cycling curves at 2 mA cm⁻² and (d) discharge/charge curves under different bending states. Reprinted with permission from Ref. [78]. Copyright© John Wiley & Sons, Inc. All rights reserved.

Figure 7

Representation of photon absorption, electron transfer, and generation of reactive species under visible−light irradiation of a Fe oxide/Fe hydroxide/N−rGO nanocomposite. Reprinted with permission from Ref. [182].Copyright©2023 Springer Nature Limited.

Figure 8

Preparation route diagram of hydrogel composites. Reprinted with permission from Ref. [187]. Copyright©2020 Elsevier B.V. All rights reserved.

Figure 9

Schematic representation of the membrane fabrication steps. Reprinted with permission from Ref. [198]. Copyright©2020 The Authors. Published by Elsevier B.V.

Figure 10

The schematic of displacement mechanism of P-GO-O. Reprinted with permission from Ref. [199]. Copyright© 2021 Elsevier Ltd. All rights reserved.

Figure 11

Functionalization of GO with aspartic acid. Reprinted with permission from Ref. [200]. Copyright©2020 The Author(s). Published by Elsevier Ltd.

Figure 12

The fabrication process of the GQD-interlayered TFN-OSN membranes. Reprinted with permission from Ref. [201]. Copyright© 2019 Elsevier B.V. All rights reserved.

Figure 13

Schematic representation of the functionalization of GO with two levels of oxidation (GO and GO_h) with Tpy using the ring-opening reaction of epoxides yielding GO–Tpy and GO_h–Tpy. Reprinted with permission from Ref. [211]. Copyright©The Royal Society of Chemistry 2021.

Figure 14

Schematic illustrating photocatalytic degradation with the help of band structures. Reprinted with permission from Ref. [213]. Copyright©2021 by the authors. Licensee MDPI, Basel, Switzerland.

Figure 15

The preparation process of graphene aerogels. Copyright© 2021 The Authors. Reprinted with permission from Ref. [214]. Published by Elsevier Ltd.

Figure 16

Plausible mechanism of CO₂ reduction by using a GrN₇₀₀–CuC catalyst. Reprinted with permission from Ref. [241]. Copyright©Royal Society of Chemistry 2023.

Figure 17

Model for the graphene/ZnV₂O₆(001) heterostructure viewed from the side (a) and the top (b). Reprinted with permission from Ref. [243]. Copyright © 2023 Elsevier B.V. or its licensors or contributors.

Figure 18

GB structure and band structure of symmetrical polycrystalline graphene. (a) Detailed GB structure of armchair-tilt (θ = 21.8°) graphene. (b) The first Brillouin zone of all structures and special K points used to calculate the band structures. (c) The corresponding band structures for the structure in (a) with different types of strains. (d) Detailed GB structure of zigzag-tilted boundary with θ = 27.8°. (e) The corresponding band structures for the structure in (d) with different types of strain. Reprinted with permission from Ref. [267]. Copyright©2023 Springer Nature Switzerland AG.