Covalently Modified Graphenes in Catalysis, Electrocatalysis and Photoresponsive Materials

Abstract

The ideal graphene is a one-atom thick single layer of carbon atoms having sp hybridation in hexagonal arrangement. Due to their large surface area and good dispersability in common solvents, graphenes are suitable platforms to anchor covalently units. The appended unit can introduce additional functionality to graphene. Although the field of covalently modified graphene is still starting compared to the development of other carbon nanoforms, there is already many examples describing the use of modified graphenes as recoverable photo-, electrocatalysts as well as in non-linear optics and to improve mechanical resistance and solubility of graphenes. In this Review, the state of the art of covalently modified graphenes for these applications is reviewed. After some general sections describing properties and characterization techniques of graphenes relevant to their use as supports and those general reactions and starting substrates to obtain the modified graphene conjugates, the main body of the review describes the preparation and properties of covalently modified graphene depending on their use as catalyst, photocatalyst, photoresponsive material, non-linear optics, electrocatalyst and other uses. The last section of the review summarizes the main achievements of the field and what should be according to our view the future developments.

Modified Nanocarbons for Catalysis

“…However, achieving this goal could have a high cost depending on the difficult of the chemical functionalization, which results in a high time‐consuming and/or expensive procedure. The chemical functionalization of graphene definitively remains a fundamental approach to obtain catalytic materials as witnessed by the very large number of publications related to this argument . Herein, an overview on some interesting examples wherein graphene was covalently modified to be used as support for different catalysts will be provided.…”

Bioinspired Electro‐Organocatalytic Material Efficient for Hydrogen Production

“…Carbon‐based materials can be produced on a large scale with lower manufacturing cost compared with metal‐based materials . In addition, carbonaceous materials often offer synergy between the material and attached active centers due to the electrical conductivity and the electron acceptor/donor properties of graphitic structure such as graphene or carbon nanotubes . Therefore, carbon‐based materials are very attractive alternatives to conventional heterogeneous electrocatalysts used for hydrogen evolution and other electrochemical reactions .…”

“…[19][20][21] In addition, carbonaceous materials often offer synergyb etween the material and attached active centers due to the electrical conductivity and the electron acceptor/donor properties of graphitic structure such as graphene or carbon nanotubes. [22] Therefore, carbon-based materials are very attractive alternatives to conventionalh eterogeneous electrocatalysts used for hydrogen evolution and other electrochemical reactions. [23,24] They are attractive not only from the economic point of view,b ut also from as cientific side.I nf act, whereas HER pathways catalyzed by metalsh ave been widely studied, [25,26] much lessi sk nown aboutt he catalytic mechanism for H 2 formation in metal-freem aterials.…”

Convenient Immobilization of Cobalt Corroles on Carbon Nanotubes through Covalent Bonds for Electrocatalytic Hydrogen and Oxygen Evolution Reactions

“…The resulting CNTse ngineered with Co corroles were used as electrocatalysts for the hydrogen evolutionr eaction (HER) and the oxygen evolution reaction (OER) in aqueous solutions of pH 0, 7, and 14. [39][40][41][42][43] Despite these progresses,h owever, convenient methods for covalenti mmobilization under mild conditions are still needed.Carbon nanotubes (CNTs) are broadly used as supports for electrochemical applications because of their large surface areas and good electrical conductivities. This is likely because the large surface area and good electricalc onductivity of CNTsc an be well preserved during the amidationr eactionu nder mild conditions.…”

“…[1][2][3] During the last decade,avariety of molecular complexes based on earth-abundant transition-metal elements including Mn, [4][5][6][7] Fe, [8][9][10][11][12][13][14] Co, [15][16][17][18][19][20][21] Ni, [22][23][24][25][26][27][28] and Cu [29][30][31][32][33] have been identified as catalystsf or these two reactions. [39][40][41][42][43] Despite these progresses,h owever, convenient methods for covalenti mmobilization under mild conditions are still needed. [34][35][36][37][38] Covalent immobilizationi su seful to improvec atalyst stabilitya nd performance and benefitst he recycling of electrocatalysts.…”