Non-Noble Metal Cored Pt-Skin Catalyst and Its Highly Enhanced Stability in Oxygen Reduction Reaction By Controlling the Nitriding Level For the Core

摘要

In this study, we introduce non-precious metals as core material for core-shell type electrocatalysts. The Pt-skin catalyst using cobalt, transition metal, as a core was nitrided to improve the stability of the electrocatalyst. Nitriding levels were systematically controlled by the adjusting of ammonia gas pressure (1, 40, 80 bar) during the heat treatment process. We obtained catalysts in which the Pt-skin structure was clearly maintained even under various preparation conditions and the average particle size of the active metal was uniformly distributed in the range of 3 to 4 nm. CoN@Pt/C catalysts have high mass activity over 0.44 mA/mg_(PGM) @ 0.9 V (vs. RHE). The most important point is not only the initial activity but also the much-improved durability. In addition, unlike the other electrocatalysts, in the accelerated stress test protocol, the change in the electrochemical surface area (ECSA) is extremely small and the ORR (oxygen reduction reaction) activity is maintained. Through the control of the nitridation level of the transition metal core, the possibility of producing a low cost, high-performance core-shell electrocatalyst was confirmed.