Reactivity Screening of Single Atoms on Modified Graphene Surface: From Formation and Scaling Relations to Catalytic Activity

Abstract

Single atom catalysts (SACs) present the ultimate level of catalyst utilization, which puts them in the focus of current research. Using density functional theory calculations, model SACs consisting of nine metals (Ni, Cu, Ru, Rh, Pd, Ag, Ir, Pt, and Au) on four different supports (pristine graphene, N‐ and B‐doped graphene and graphene with single vacancy) are analyzed. Only graphene with a single vacancy enables the formation of SACs, which are stable in terms of aggregation and dissolution under electrochemical conditions. Reactivity of models SACs is probed using atomic (hydrogen and A = C, N, O, and S) and molecular adsorbates (AHx, x = 1, 2, 3, or 4, depending on A). Scaling relations between adsorption energies of A and AHx on model SACs are confirmed. However, the scaling is broken for CH3. There is also an evident scaling between adsorption energies of atomic and molecular adsorbates on metals SAs supported by pristine, N‐doped and B‐doped graphene, which originates from similar electronic structures of SAs on these supports. Using the obtained data, the authors analyze the hydrogen evolution on the model SACs. Only M@graphene vacancy systems (excluding Ag and Au) are stable under hydrogen evolution conditions in highly acidic solutions.

What Is the Real State of Single-Atom Catalysts under Electrochemical Conditions—From Adsorption to Surface Pourbaix Plots?

“…The strongest M binding (Ir) case corresponded to the maximum charge transfer from M to graphene (Table 1). By comparing the metal embedding energies and the corresponding cohesive energies (experimental data [35], Figure 2), it can be concluded that the majority of the studied metals were less susceptible to dissolution when embedded into vG than the corresponding bulk phase, which is in agreement with our previous findings [36]. The exceptions are Ag and Au, which have lower embedding energies than the cohesive energies of bulk phase (absolute values).…”

Investigation of the Stability and Hydrogen Evolution Activity of Dual-Atom Catalysts on Nitrogen-Doped Graphene

“…According to the Sabatier principle, the closer to zero (| | ≤ 0.10), the higher catalytic activity of HER [ 29 , 30 , 49 ]. If the interaction between H and the catalyst is too weak ( ≫ 0), hydrogen adsorption (Volmer reaction: , where * refers to catalysts surface) will be limited, while too strong interaction ( ≪ 0) creates difficulty for the desorption step (Tafel or Heyrovsky step: or ) to proceed on the catalyst surface [ 50 , 51 ]. Based on these results, we calculated by considering the H adsorption on the stable SACs ( TM 1 − SVGN 3 )/DACs ( TM 2 − SVGN 3 ) models.…”

“…It also provides useful information to design DACs on the SVGN 3 surface for HER beyond SACs. Furthermore, we also found that both the electrochemical conditions and the lattice/matrix in which the metals are embedded affect the stability and HER activity of atomically-dispersed metal catalysts [ 51 , 53 ]. In future work, we will further consider the effect of the real environment on the stability and catalytic activity.…”

Introduction of Near to Far Infrared Range Direct Band Gaps in Graphene: A First Principle Insight

“…Behavior of trap states due to carbon vacancies and the stability of graphene with such antidots are also not discussed in detail in these earlier studies. It is worth highlighting that the unbound orbitals of the carbon atoms near antidots can easily react with ambient reactive gases like oxygen, which can change graphene’s intrinsic properties and can also make it unstable. − Hence, a promising band gap engineering method in graphene is still in demand, which can give significant band gap tunability without noticeable distortion of its intrinsic properties as well as planar structure while offering a reliable and experimentally feasible approach. In this work, by using density functional theory (DFT)-based computations, we have done systematic investigations on vacancy-assisted band gap engineering of graphene while addressing reliability, stability, and mid-gap (trap) state-related issues using post defect hydrogenation and fluorination of vacancy sites.…”