Defect Engineering for Fuel‐Cell Electrocatalysts

Abstract

The commercialization of fuel cells, such as proton exchange membrane fuel cells and direct methanol/formic acid fuel cells, is hampered by their poor stability, high cost, fuel crossover, and the sluggish kinetics of platinum (Pt) and Pt‐based electrocatalysts for both the cathodic oxygen reduction reaction (ORR) and the anodic hydrogen oxidation reaction (HOR) or small molecule oxidation reaction (SMOR). Thus far, the exploitation of active and stable electrocatalysts has been the most promising strategy to improve the performance of fuel cells. Accordingly, increasing attention is being devoted to modulating the surface/interface electronic structure of electrocatalysts and optimizing the adsorption energy of intermediate species by defect engineering to enhance their catalytic performance. Defect engineering is introduced in terms of defect definition, classification, characterization, construction, and understanding. Subsequently, the latest advances in defective electrocatalysts for ORR and HOR/SMOR in fuel cells are scientifically and systematically summarized. Furthermore, the structure–activity relationships between defect engineering and electrocatalytic ability are further illustrated by coupling experimental results and theoretical calculations. With a deeper understanding of these complex relationships, the integration of defective electrocatalysts into single fuel‐cell systems is also discussed. Finally, the potential challenges and prospects of defective electrocatalysts are further proposed, covering controllable preparation, in situ characterization, and commercial applications.

Defects Enhance the Electrocatalytic Hydrogen Evolution Properties of MoS2‐based Materials

“…Point defects refer to the deviation of the crystal surface from the normal crystallographic arrangement in the node or adjacent area. [19,20] In electrocatalysis, especially in MoS 2 catalysts, zero-dimensional defects play a vital role. According to the origin of defects, point defects can be divided into doped defects and intrinsic defects.…”

“…Thus, they can be used to control electrocatalytic performance by altering the species, contents, and locations of defects. [19] Wang's group provided basic guidance for the design of defect-containing electrocatalysts through an in-depth understanding of structure-reactivity relationships. [20] Lu's group designed controllable nitrogen-doped carbon-dotloaded MoP nanoparticles for promoting the HER in alkaline media.…”

Defect Engineering of Carbon‐based Electrocatalysts for Rechargeable Zinc‐air Batteries

“…Intrinsic defects are intrinsic components of crystals, and non-inherent defects are mainly caused by the heteroatoms or metal atoms doping and their combination sites. [14,39] Reproduced with permission. [14,29] Copyright 2020, Wiley-VCH; Copyright 2015, ACS.…”

Defect Chemistry on Electrode Materials for Electrochemical Energy Storage and Conversion

“…The defect in catalyst supports can improve the electrical conductivity and enhance the interaction between metal nanoparticles and the supports. In addition, Wang's group also summarized the work of electrocatalysts for fuel cells in recent years from the point of view of their defective structure and catalytic mechanism [37] …”