Single Metal Atoms Anchored in Two‐Dimensional Materials: Bifunctional Catalysts for Fuel Cell Applications

Abstract

Single metal atoms doped in two‐dimensional materials have attracted particular attention for various catalytic reactions, due to their unique properties beyond metal catalysts. Herein we present density functional theory (DFT) calculations to study a wide range of such systems for oxygen reduction reaction (ORR) and hydrogen oxidation reaction (HOR) for application in cathode and anode of fuel cell, respectively. We find that the scaling relation of adsorption free energies of relevant ORR intermediates changes in the direction of improved activity. By considering more than 50 combinations, various ORR and HOR candidates are identified with improved catalytic activities compared to the state‐of‐the‐art Pt (111). Particularly, Rh embedded in N‐doped graphene is predicted to be markedly active for bifunctional fuel cell catalysis. This work highlights the potential of these systems as new classes of electrocatalysts to maximize the ORR catalytic activity and alleviate the use of precious metals

Computational Screening of Efficient Single‐Atom Catalysts Based on Graphitic Carbon Nitride (g‐C3N4) for Nitrogen Electroreduction

“…Specifically, the first hydrogenation step (NNH* formation) is the PDS on Co@C 3 N 4 and Mo@C 3 N 4 , while the last step (desorption of NH 2 *) is the PDS on Ti@C 3 N 4 , Pt@C 3 N 4 , and W@C 3 N 4 . Among all these promising candidates, W@C 3 N 4 has the lowest ∆ G PDS value of 0.35 eV, which is 0.63 eV lower than that on Ru (0001) and is comparable (even lower) to other recently proposed efficient SACs, such as single Mo atom supported on defective boron nitride nanosheet (0.35 eV),[15f] or N‐doped carbon (0.40 eV),[15h] the single Ti atom anchored on N‐doped graphene (0.69 eV), and on defective g‐C 3 N 4 …”

“…This finding indicates that the catalytic activity of SACs cannot be evaluated only by the N 2 adsorption strength on catalyst surfaces, instead, both the NNH* formation and NH 2 * desorption should also be examined. [4e,15f]…”

“…To achieve a good SAC, we not only need suitable single atoms, but also need to deliberately select an appropriate substrate that can strongly interact with the metal atoms. Since the successful synthesis of graphene in 2004, many 2D materials have been widely utilized as promising substrates for metal atoms in catalysts due to their unique physical and chemical properties, such as high specific surface area, good mechanical and thermal stability . However, pristine graphene is not a good substrate since the metal atoms diffuse easily to form agglomerated particles on its surface, which greatly reduce the catalytic active sites.…”

Catalysis-hub.org: An Open Electronic Structure Database for Surface Reactions

“…It also serves to make these results easily available to the public and other researchers for aiding in new catalytic discoveries. We are focusing on chemical reactions of interest for sustainable energy applications such as conversion of CO 2 and synthetic gas to fuels [15,16], electrochemical fuel cells [17,18], and production of fuels and chemicals from electrochemical approaches [19]. The catalytic materials of interest for these applications includes transition metals and alloys, metal-oxides and oxy-hydroxides, perovskites, layered 2D materials, and metal-chalcogenites.…”

“…Also, a collection of soon to be published/just submitted datasets are made available. Recently featured datasets include studies of syngas to C+ Oxygenates conversion on transition metals [16], oxygen reduction and hydrogen oxidation on metal-doped 2D materials [18] and a study of solvated protons at the water-metal interface [23]. As a whole, the database contains roughly 700 different chemical reactions, involving more that 150 chemical species and 3,500 different catalytic material surfaces.…”