DFT-Based Study on Oxygen Adsorption on Defective Graphene-Supported Pt Nanoparticles

Abstract

The structural and electronic properties of Pt13 nanoparticles adsorbed on monovacancy defective graphene have been determined to understand oxygen adsorption on Pt nanoparticles based upon density functional theory predictions using the generalized gradient approximation. We demonstrate that a monovacancy site of graphene serves a key role as an anchoring point for Pt13 nanoparticles, ensuring their stability on defective graphene surfaces and suggesting their enhanced catalytic activity toward the interaction with O2. Strong hybridization of the Pt13 nanoparticle with the sp2 dangling bonds of neighboring carbon atoms near the monovacancy site leads to the strong binding of the Pt13 nanoparticle on defective graphene (−7.45 eV in adsorption energy). Upon both adsorption of the Pt13 nanoparticle on defective graphene and O2 on Pt13–defective graphene, strong charge depletion of the Pt atom at the interfaces of Pt–C and Pt–O2 is observed. Pt13 nanoparticles are able to donate charge to both defective graphene and O2. The Pt13–defective graphene complex shows an O2 adsorption energy of −2.30 eV, which is weaker than the O2 adsorption energy of −3.92 eV on a free Pt13 nanoparticle. Considering the strong stability of the Pt nanoparticles and relatively weaker O2 adsorption energy due to the defective graphene support, we expect that the defective graphene support may increase the catalytic activity of Pt nanoparticles compared to flat Pt metal surfaces, not only by preventing sintering of Pt nanoparticles due to the strong anchoring nature of the graphene defect sites but also by providing a balance in the O2 binding strength that may allow for enhanced catalyst turnover.

Mechanisms of the Oxygen Reduction Reaction on Defective Graphene-Supported Pt Nanoparticles from First-Principles

“…The isolated Pt 13 13 -defective graphene are discussed in our previous study. 15 Fully relaxed and optimized Pt 13 -defective graphene systems were partially frozen for this ORR study to save computational effort. The boundary 83 carbon atoms out of 127 carbon atoms of defective graphene were frozen based on its negligible influence on O 2 adsorption and geometry change as shown in Supporting Information, Computational Methodology section 2 ( Figure S1 and Figure S2).…”

“…Furthermore, the vacancy sites in graphene can serve as anchoring points for the growth of nanoparticles. 14,15 Defective graphene-supported nanoparticles may enhance surface reactivity 14,16 and previous experimental studies have shown that atomic defects in graphene may be formed after several tens of seconds of irradiation with an electron beam 17 or by treatment with hydrochloric acid. 18 The mechanisms of the ORR have been investigated experimentally and theoretically for Pt and Pt alloy catalysts.…”

Ab-<i>initio</i> studies of adsorbate-surface interactions

“…12 and a trigonal pyramid by Ref. 13 Only the following larger-size clusters have been investigated: Pd-Au with n = 7; 137 Co, 138 Pt, 14 Fe, Co, Ni, 16 and MPd 12 (M = Fe, Co, Ni, Cu, Zn, Pd),, 15 and Au 49 . 139 These limitations, complexity, and controversies call for systematic study of TM n clusters on Gr sheet, to identify trends and classify the interactions between TM clusters and Gr.…”

“…37 Even though, many theoretical studies have been conducted to describes the geometrical and eletronic properties of (TM) clusters on Gr support, they agree and disagree on many points. [8][9][10][11][12][13][14][15][16] To our knowledge, the dependence of structural and adsorption properties on cluster size has never been systematically studied from a theoretical perspective. These limitations, complexity, and controversies call for systematic study of TM n clusters on Gr sheet, to identify trends and classify the interactions between TM clusters and Gr.…”

“…Existem muitos estudos teóricos na literatura que descrevem a interação desse tipo de aglomerado com uma folha de grafeno, porém há numerosas discordâncias. [8][9][10][11][12][13][14][15][16] Tais controvérsias parecem suplicar por um estudo sistemático. Nesta tese focamos nossos estudos nas interações superfície-superfície e de átomos ou aglomerados atômicos com superfícies de carbono e de um metal.…”