Intrinsic ORR Activity Enhancement of Pt Atomic Sites by Engineering the d‐Band Center via Local Coordination Tuning

Abstract

A considerable amount of platinum (Pt) is required to ensure an adequate rate for the oxygen reduction reaction (ORR) in fuel cells and metal‐air batteries. Thus, the implementation of atomic Pt catalysts holds promise for minimizing the Pt content. In this contribution, atomic Pt sites with nitrogen (N) and phosphorus (P) co‐coordination on a carbon matrix (PtNPC) are conceptually predicted and experimentally developed to alter the d‐band center of Pt, thereby promoting the intrinsic ORR activity. PtNPC with a record‐low Pt content (≈0.026 wt %) consequently shows a benchmark‐comparable activity for ORR with an onset of 1.0 VRHE and half‐wave potential of 0.85 VRHE. It also features a high stability in 15 000‐cycle tests and a superior turnover frequency of 6.80 s−1 at 0.9 VRHE. Damjanovic kinetics analysis reveals a tuned ORR kinetics of PtNPC from a mixed 2/4‐electron to a predominately 4‐electron route. It is discovered that coordinated P species significantly shifts d‐band center of Pt atoms, accounting for the exceptional performance of PtNPC.

A theoretical roadmap for the best oxygen reduction activity in two-dimensional transition metal tellurides

“…50,[65][66][67][68][69][70] As we already know that the partially filled pz orbital is responsible for the Te-O interactions upon O2 adsorption, we introduced a descriptor εpz defined as a centroid of the projected density of states of the pz orbital relative to the Fermi level analog to d-band center. [71][72][73][74][75] As presented in Figure 4c-d, εpz of the active Te atoms shows reasonable linear relationship to the adsorption energies of O2 and intermediate oxygen-containing adsorbates. The linear relationships between ΔGO2 and other possible descriptors, such as the p-band center εp, are also calculated as shown in Figure S18, all of which are inferior to that of εpz.…”

Highly-dispersed and high-metal-density electrocatalysts on carbon supports for the oxygen reduction reaction: from nanoparticles to atomic-level architectures

“…For example, in ORR catalytic process, monatomic Pt catalyst often cannot effectively catalyze the fracture of O-O bond, so it is difficult to effectively catalyze ORR in four-electron mechanism [44]. Due to the inability of isolated Pt single atom to break the O-O bond through lateral adsorption, the ORR tends to be two-electron product (H 2 O 2 ) rather than four-electron product (H 2 O) required by fuel cells [45]. High-metal density (high loading) Pt SACs shows excellent ORR performance (with much higher mass activity) than low-metal density commercial carbon-supported Pt catalysts (40 wt.% Pt) regarding their activity and stability for ORR under rotating ring disk electrode (RRDE) have been systematically evaluated (see Fig.…”

“…However, some of the current carbon-supported SACs cannot provide enough reaction sites in ORR catalytic reactions due to their low metal loading [44][45][46]. Generally, at least two adjacent metal atoms (i.e., two adjacent active centers) need to cooperate effectively to promote the efficient fourelectron mechanism.…”

Carbon Aerogels as Electrocatalysts for Sustainable Energy Applications: Recent Developments and Prospects

“…Obviously, a catalyst that promotes the four-electron transfer reaction is what we need. Currently, platinum (Pt)-based catalysts are still the best catalysts for ORR, usually synthesized by dispersing Pt nanoparticles onto carbon supports to solve the problem of the reduced exposed active surface due to aggregation and non-uniform dispersion of platinum nanoparticles [ 46 , 47 , 48 , 49 ]. Highly active Pt/C catalysts have been commercialized.…”