Noble metal supported hexagonal boron nitride for the oxygen reduction reaction: a DFT study

Abstract

Discovering active, stable and cost-effective catalysts for the oxygen reduction reaction (ORR) is of utmost interest for commercialization of fuel cells. Scarce and expensive noble metals such as Pt and Pd are the state-of-the-art active ORR catalysts but suffer from low stability against CO poisoning. Hexagonal boron nitride (h-BN) is a particularly attractive material due to its low cost and stability; however, it suffers from intrinsic low activity toward the ORR in the pristine form as a result of its inherently low conductivity with a large band gap of $5.5 electron volts. During the past few years, several strategies such as using metal supports, metal doping and atomic vacancies have been reported to significantly increase the conductivity, thereby promoting the ORR activity. Herein we use density functional theory calculations to systematically study these strategies for activating inert h-BN and further examine the stability against CO poisoning. We show that noble metals, such as Ag, Pd, and Pt, require boron (B) or nitrogen (N) vacancies to reasonably activate h-BN toward the ORR. For example, Pd supported h-BN with B-vacancies exhibits significantly high ORR activity. All three examined metal supported h-BNs are predicted to be stable against CO poisoning. These results demonstrate that supporting h-BN on noble metals is a promising strategy to increase the stability against CO poisoning while maintaining high ORR activity. Fig. 1 The optimized geometries of metal supported BN with and without vacancies using a 2(O3 Â O3) supercell (top) for Ag, Pd, and Pt and a (3 Â 3) supercell for Cu (bottom). Blue and pink balls indicate N and B, respectively.This journal is

Vacancy in Ultrathin 2D Nanomaterials toward Sustainable Energy Application

“…Symbols ●, ▲, ♦, and ■ indicate Ag, Cu, Pd, and Pt supports, respectively. Reproduced with permission . Copyright 2019, The Royal Society of Chemistry.…”

“…In addition, depending on the structure of these materials, vacancy engineering can be used to fine‐tune or tailor properties according to the specific needs of the application. For materials featuring X a and X a Y b structures, vacancy engineering is primarily used to adjust the energy band structure and regulate the electronic environment around vacancies 13a,d,44. In M a X b and M a X b Y c structures, X and Y vacancies can be used to regulate the adsorption energy of reaction intermediates, and to optimize ion diffusion paths, which renders each vacancy a catalytic active site 28,42e,45.…”

“…The deposition of X a Y b materials, such as h ‐BN, on precious metal supports can enhance catalytic stability while maintaining catalytic activity . The effects of boron and nitrogen vacancies on the ORR in h ‐BN deposited on various supports ( h ‐BN@M, M = Ag, Cu, Pd, and Pt) have been studied with DFT calculations . These studies have shown that the appearance of vacancies is not conducive to increased ORR activity when the substrate possesses a medium affinity for oxygen adsorption (like Cu).…”

Functionalization of 2D materials for enhancing OER/ORR catalytic activity in Li–oxygen batteries

“…The emergence of two-dimensional (2D) materials over recent years has offered a number of promising candidates for improving the electrocatalysis of ORR/OER due to their high specific surface area and high surface density of active catalytic sites. Some materials of interest to Li-O 2 batteries are nitrogen-doped graphene 26 , hexagonal boron nitride (h-BN) on Ni surfaces 14,27 , and molybdenum carbide (Mo 2 C) 28 . Layered transition metal-carbide and metalnitrite MXenes with the general formula of M n+1 X n , with M being a transition metal and X = {C, N}, are highly stable 2D materials containing 2n + 1 layers of atoms 29 (see Supplementary Fig.…”

Synthesis and Modification of Boron Nitride Nanomaterials for Electrochemical Energy Storage: From Theory to Application

“…This demonstrated the inertness of pure BN and verified that the interaction between BN and the Au substrate is a major influencing factor, which is consistent with Uosaki's experiment and previous theoretical results. [ 187,188,192 ] A similar work has been conducted by Banks and co‐workers [ 237 ] For C‐based substrates, it was found that the ORR catalytic activity of 2D h‐BN was highly dependent on the C material and cover/mass ratio. The h‐BN modified screen‐printed graphite electrode (SPE) showed a better electrochemical response than the GC‐ and B‐doped diamond electrodes.…”