Recently, the research team of Deng Tao of the School of Materials Science and Engineering of Shanghai Jiaotong University has made significant progress in the in-situ liquid-phase corrosion of fuel cell nanoelectrocatalysts. The team used transmission electron microscope to study the dynamic process of fuel cell corrosion in real time. The inactivation mechanism of the catalyst in the application of electrocatalytic reaction was revealed, which has important guiding significance for the design of high stability catalyst.
With the rapid development of fuel cells in recent years, there is an urgent need to find a highly active and highly stable fuel cell catalyst. However, high activity catalysts are mostly formed by the use of active metals and platinum alloys to form metal binary or polybasic solid solutions or cores. The shell structure, with the progress of electrocatalytic reaction, there will appear a large number of persistent corrosion of the active metal components, thus destroying the optimal alloy composition, greatly reducing the reactivity of the metal catalyst, and seriously affecting the stability of the catalyst. The evolution process and mechanism of fuel cell corrosion are necessary.
Fig.1 Three kinds of in-situ corrosion of Pd@Pt nanocube particles in TEM liquid phase environment
(a) No defects (b) Angular defects (c) Face defects
Fig. 2 Comparison of corrosion rates of three Pd@Pt nanocube particles
The team used in-situ transmission electron microscopy to observe the corrosion process of Pd@Pt cubic electrocatalysts in three different structures (without defects, corner defects, and surface defects) in liquid phase in real time. Galvanic and halogen corrosion studies were found. Both corrosion modes result in the corrosion dissolution of the Pd nucleus within the particles and the formation of a Pt cubic shell. Further studies have shown that galvanic corrosion preferentially occurs at the corners of the lower surface energy at the lower surface of the coordination angle. Slow erosion in the direction of the center; halogen corrosion is a rapid corrosion along the defect direction caused by Br- ions in the surrounding liquid phase environment, and there is a competition and restriction relationship between it and galvanic corrosion. Defective inhibition control is the key to improving the stability of such atomic layer core-shell electrocatalysts due to corrosion. This study has important guiding significance for the design of high stability fuel cell catalysts and opens up the use of in situ characterization techniques to study catalyst stability. Sexual new means.