Strategies for improving stability of Pt-based catalysts for oxygen reduction reaction

Proton exchange membrane fuel cells (PEMFCs), which can directly convert chemical energy into electrical energy with high efficiency and zero carbon emission, have attracted extensive attention. Unfortunately, the sluggish kinetics of oxygen reduction reaction (ORR) on the cathode leads to considerable overpotential and thus severely lowering its operational energy conversion efficiency. Although Pt-based catalysts have been developed as the most efficient catalyst towards ORR, however, their stability is far from the application requirements, which hinders the large-scale application of PEMFCs to a certain extent. Thus, improving the stability of Pt-based catalysts is urgently desirable to advance the widespread commercialization of fuel cells. This review focuses on the stability of Pt-based ORR catalysts in PEMFCs, from the perspectives of catalyst degradation mechanism and stability improvement strategies. It is aimed at providing research directions for the development of stable Pt-based catalysts. Firstly, degradation of metal nanoparticles (dissolution, migration, agglomeration, Ostwald ripening, etc.) and corrosion of carbon supports are introduced. To conquer the two attenuation mechanisms, stability improvement strategies such as constructing intermetallic compounds, enhancing metal-support interaction and the modification of carbon support, are summarized in detail. In addition, some typical stability characterization techniques are outlined. Finally, we discuss the challenges and possible research directions in the future. We hope this review can help readers gain insights into the stability issues of Pt-based ORR nanocatalysts and encourage research that will enable the commercialization of PEMFCs.