Enhancing Oxygen Reduction Activity of Pt‐based Electrocatalysts: From Theoretical Mechanisms to Practical Methods

Abstract

Pt‐based electrocatalysts are considered as one of the most promising choices to facilitate the oxygen reduction reaction (ORR), and the key factor enabling their success is to reduce the required amount of platinum. Herein, we focus on illuminating both the theoretical mechanisms which enable enhanced and sustained ORR activity and the practical methods to achieve them in catalysts. The various multi‐step pathways of ORR are firstly reviewed and the rate‐determining steps based on the reaction intermediates and their binding energies are analyzed. We then explain the critical aspects of Pt‐based electrocatalysts to tune oxygen reduction properties from the viewpoints of active sites exposure and altering the surface electronic structure, and further summarize representative research progress towards practically achieving these activity enhancements with a focus on platinum size reduction, shape control and core Pt elimination methods. We finally outline the remaining challenges and provide our perspectives with regard to further enhancing their activities.

Tuning of Trifunctional NiCu Bimetallic Nanoparticles Confined in a Porous Carbon Network with Surface Composition and Local Structural Distortions for the Electrocatalytic Oxygen Reduction, Oxygen and Hydrogen Evolution Reactions

“…The lowest unit cell volume value of Ni 0.25 Cu 0.75 /C reflects that the lattice contraction, and therefore, the high strain energy strongly helps to improve the ORR catalytic rates as well as to reduce the binding energy of oxygen-based adsorbates, such as O* and OH*, thus increasing the electron transfer rates at the catalytically active surface sites. 58,59 Our DFT calculations showed a good agreement with the experimental results. In detail, a significant reduction of the Gibbs free energies for the O*, OH*, and OOH* intermediate catalytic species was observed (Figure 7F).…”

Effect of Crystal Growth on the Thermodynamic Stability and Oxygen Reduction Reaction Activity of Cu–Pt Nanoparticles

“…This enhancement has also been attributed to a Pt-rich shell and a stable intermetallic ordered core . Among these structurally ordered phases, extensive research has been done on the L1 0 /L1 1 and the cubic ordered L1 2 /L1 3 phases (L1 0 , L1 1 , etc., are Strukturbericht designations) because of the availability of multiple degrees of freedom and the pure Pt shell thickness, which enable activity tunability for ORR. − For example, L1 0 ordered CoPt and FePt, and ordered-L1 2 CoPt 3 and CrPt 3 have demonstrated an improved ORR activity relative to their face centered cubic (fcc)/A 1 disordered phase counterparts. Typically, these ordered phases are synthesized by annealing ,− of the disordered phase to high temperatures (650 or 800 °C − ) during which the disorder–order phase transformation is also dependent on the NPs’ composition.…”

Non-aqueous solution synthesis of Pt-based nanostructures for fuel cell catalysts

“…First, excessive usage of scarce Pt makes it challenging to reduce cost [5][6][7][8]. Second, the slow kinetics of cathodic oxygen reduction reaction (ORR) restrict the improvement of overall catalytic efficiency [9][10][11].…”

“…The porous nanostructures can suppress aggregation to enhance the durability [23]. Many reviews in the past few years mostly focused on the structure-property relationships and the strategies to enhance the catalytic performance [9,10,13,18,[23][24][25][26][27]. However, the synthesis of Pt-based nanostructures has not been systematically summarized yet.…”