Practical Classification of Catalysts for Oxygen Reduction Reactions: Optimization Strategies and Mechanistic Analysis

Abstract

Oxygen reduction reaction (ORR) is the core reaction of fuel cell/metal-air battery at the cathode, and it is of great significance to develop high-performance ORR catalyst. Generally speaking, ORR catalysts are classified according to the class of materials they use, which often makes it difficult for different types of catalysts to have a clear connection with some unified optimization mechanism and creates difficulties in designing improvement strategies. Here, this review proposes three major strategies that can affect the activity of ORR catalysts: designing morphology, defect control, and heteroatom doping. The core content of this review is to analyze the principles of various optimization strategies that affect the performance of catalysts individually or synergistically at the micro level. In addition, the problems and challenges still faced in the design of ORR catalysts are sorted out, and possible solutions are proposed. This review makes the research direction of ORR catalysts clearer, and provides theoretical support and new ideas for the design of high-efficiency electrocatalysts.

General Design Concept of High‐Performance Single‐Atom‐Site Catalysts for H2O2 Electrosynthesis

“…[ 288–291 ] Electrosynthesis of H 2 O 2 includes 2e − ORR and 2e − WOR pathways and the selectivity of both pathways depends on the catalyst‐to‐intermediate interactions. [ 292–295 ] As described in Chapter two, the key to obtaining high activity and selectivity for 2e − ORR is retaining the O‐O bond and adsorbed *OOH with suitable strength. Therefore, the end‐on adsorption configuration and ΔG *OOH of 4.22 eV near the peak of the volcano plot are the key issues in 2e − ORR studies.…”

Spray Pyrolysis Regulated FeCo Alloy Anchoring on Nitrogen–Doped Carbon Hollow Spheres Boost the Performance of Zinc–Air Batteries

“…Metal-air batteries, especially rechargeable Zn-air batteries (RZABs), are considered to be the most promising energy storage and conversion devices owing to their high energy density (1084 Wh kg −1 ), low price, DOI: 10.1002/smll.202310318 environmental friendliness and good safety. [1,2] However, oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) on the air electrode possess slow reaction kinetics. Their high overpotential leads to lower energy density and the conversion efficiency of the RZAB.…”

Modification of NiSe2 Nanoparticles by ZIF-8-Derived NC for Boosting H2O2 Production from Electrochemical Oxygen Reduction in Acidic Media

“…As is generally known, ORR is an electrocatalytic reaction proceeding with a four-electron (4e − ) pathway or two-electron (2e − ) pathway when applying different electrocatalysts. The 4e − ORR reaction has been intensively studied and applied in battery conversion systems such as fuel cells or metal-air batteries [9][10][11], while the development of efficient electrocatalysts for the selective 2e − ORR pathway toward H 2 O 2 remains challenging at present [1,9].…”