Quasi‐Paired Pt Atomic Sites on Mo₂C Promoting Selective Four‐Electron Oxygen Reduction

Abstract

Atomically dispersed Pt species are advocated as a promising electrocatalyst for the oxygen reduction reaction (ORR) to boost noble metal utilization efficiency. However, when assembled on various substrates, isolated Pt single atoms are often demonstrated to proceed through the two-electron ORR pathway due to the unfavorable O─O bond cleavage thermodynamics in the absence of catalytic ensemble sites. In addition, although their distinct local coordination environments at the exact single active sites are intensively explored, the interactions and synergy between closely neighboring single atom sites remain elusive. Herein, atomically dispersed Pt monomers strongly interacting on a Mo 2 C support is demonstrated as a model catalyst in the four-electron ORR, and the beneficial interactions between two closely neighboring and yet non-contiguous Pt single atom sites (named as quasi-paired Pt single atoms) are shown. Compared to isolated Pt single atom sites, the quasi-paired Pt single atoms deliver a superior mass activity of 0.224 A mg −1 Pt and near-100% selectivity toward four-electron ORR due to the synergistic interaction from the two quasi-paired Pt atom sites in modulating the binding mode of reaction intermediates. Our first-principles calculations reveal a unique mechanism of such quasi-paired configuration for promoting four-electron ORR.

Nurturing the marriages of single atoms with atomic clusters and nanoparticles for better heterogeneous electrocatalysis

“…Very recently, we have found the effective elongation of the O–O bond in an *OOH adsorbate over two quasi‐paired Pt single atoms supported on a Mo 2 C substrate, as seen in ORR, which proves to be several‐fold more effective than by either the single Pt atom or the Pt‐Pt dimer. [ 28 ]…”

“…Like the atomic dimers, such quasi‐paired Pt single atoms are also able to facilitate 4e − ORR through inter‐site synergistic interactions. [ 64 ]…”

“…Like the atomic dimers, such quasipaired Pt single atoms are also able to facilitate 4e − ORR through inter-site synergistic interactions. [64] The coordination and local environment of atomic dimer/trimers on the support are important considerations. Interestingly, it has been verified by DFT calculations and in situ XANES spectroscopy that the OH over dual sites could be spontaneously formed and served as the modifying ligands to enable dimers more active.…”

Emerging Ultrahigh‐Density Single‐Atom Catalysts for Versatile Heterogeneous Catalysis Applications: Redefinition, Recent Progress, and Challenges

“…However, due to the lack of multiple atom-connected ensemble sites, low-density SACs are not competent in some multistep complex catalytic reactions. [38,39] For example, in the oxygen reduction process, low-density SACs often cannot effectively catalyze the fracture of O─O bond, so it is difficult to effectively catalyze four-electron oxygen reduction. [38] Besides, two adjacent heterogeneous metal atoms can simultaneously activate and adsorb different species in the catalytic hydrogenation of 4-nitrostyrene that the routine structure with O atom bridging and partial metal bond.…”

“…[ 38,39 ] For example, in the oxygen reduction process, low‐density SACs often cannot effectively catalyze the fracture of OO bond, so it is difficult to effectively catalyze four‐electron oxygen reduction. [ 38 ] Besides, two adjacent heterogeneous metal atoms can simultaneously activate and adsorb different species in the catalytic hydrogenation of 4‐nitrostyrene that the routine SACs are incompetent. [ 39 ] At this time, the proposal of AFCs with ensemble‐like 3D sites may be a turning point and new stage for the atomic catalysis systems.…”