Graphene, the reincarnation of a surface, offers new opportunities in catalytic applications, not only because of its peculiar electronic structure, but also because of the ease of modulating it. A vast number of proposals have been made to support this point, but there has been a lack of a systematic understanding of the different roles of graphene, as many other reviews published have focused on the synthesis and characterization of the various graphene-based catalysts. In this review, we surveyed the vast literature related to various theoretical proposals and experimental realizations of graphene-based catalysts to first classify and then elucidate the different roles played by graphene in solid-state heterogeneous catalysis. Owing to its one-atom thickness and zero bandgap with low density of states around Fermi level, graphene has great potential in catalysis applications. In general, graphene can function as a support for catalysts, a cover to protect catalysts, or the catalytic center itself. Understanding these functions is important in the design of catalysts in terms of how to optimize the electronic structure of the active sites for particular applications, a few case studies of which will be presented for each role.

Graphene-based solid-state catalysis is an emerging direction in research on graphene, which opens new opportunities in graphene applications and thus has attracted enormous interests recently. A central issue in graphene-based catalysis is the lack of an effective yet practical way to activate the chemically inert graphene, which is largely due to the difficulties in the direct treatment of graphene (such as doping transition metal elements and introducing particular type of vacancies). Here we report a way to overcome these difficulties by promoting the reactivity and catalytic activity of graphene via substrate engineering. With thorough first-principles investigations, we demonstrate that when introduce a defect, either a substitutional impurity atom (e.g. Au, Cu, Ag, Zn) or a single vacancy, in the underlying Ru (0001) substrate, the reactivity of the supported graphene can be greatly enhanced, resulting in the chemical adsorption of O₂ molecules on graphene. The origin of the O₂ chemical adsorption is found to be the impurity- or vacancy-induced significant charge transfer from the graphene–Ru (0001) contact region to the 2π* orbital of the O₂ molecule. We then further show that the charge transfer also leads to high catalytic activity of graphene for chemical reaction of CO oxidation. According to our calculations, the catalyzed CO oxidation takes place in Eley-Rideal (ER) mechanism with low reaction barriers (around 0.5 eV), suggesting that the substrate engineering is an effective way to turn the supported graphene into an excellent catalyst that has potential for large-scale industrial applications.

Reducing the dimensionality of transition metal dichalcogenides to one dimension opens it to structural and electronic modulation related to charge density wave and quantum correlation effects arising from edge states. The greater flexibility of a molecular scale nanowire allows a strain-imposing substrate to exert structural and electronic modulation on it, leading to an interplay between the curvature-induced influences and intrinsic ground-state topology. Herein, the templated growth of MoS₂ nanowire arrays consisting of the smallest stoichiometric MoS₂ building blocks is investigated using scanning tunnelling microscopy and non-contact atomic force microscopy. Our results show that lattice strain imposed on a nanowire causes the energy of the edge states to oscillate periodically along its length in phase with the period of the substrate topographical modulation. This periodic oscillation vanishes when individual MoS₂ nanowires join to form a wider nanoribbon, revealing that the strain-induced modulation depends on in-plane rigidity, which increases with system size.

A heterogeneous Pt single-atom catalyst promotes E-selective synthesis of hydrazones en route to bioactive 1 H -indazoles.

With the ongoing effort in proposing and realizing functional two-dimensional (2D) materials, we predict by first-principles calculations a family of 2D metal-carbon (M–C) crystals consisting of M–C trigonal lattice interpenetrated with the metal buckled honeycomb structure. We suggest by simulations that the 2D M–C crystals can be readily fabricated by a self-organizing lattice reconstruction process after placing metal atoms on hollow sites of γ-graphyne. In total, we found 12 members of the family and they exhibit a variety of electronic and magnetic properties. In this work, we highlight and focus on the Fe member of the family, 2D-Fe₂C₁₂. Each Fe in 2D-Fe₂C₁₂ has a magnetic moment of 1 μ_B due to the spin splitting of Fe E1 bands at Fermi surface, resulting in half metallicity and high catalytic activity with unusually high-density single-atom Fe active sites. Ab initio molecular dynamics simulations revealed that the 2D-Fe₂C₁₂ retains its structural integrity up to 700 K of simulated short duration annealing. We expect these results to stimulate experimental research for the 2D M–C crystals we proposed.