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

Abstract

Cost reduction is a key barrier for the commercialization of fuel cells, and the adaption of Core-shell type electrocatalysts is expected to play a major role. Core-shell electrocatalysts have shown remarkable results in terms of activity as well as durability. Electrocatalysts using Pd as a core material has been representative model. It is also announced that durability as well as activity is improved through the use of alloyed or doped Pd cores. In recent years, however, there is a request for a Pt-skin type electrocatalyst which does not use expensive Noble metals. Low-cost transition metals are considered candidates for core materials, but durability is still a challenging issue. In this study, we introduced Co as a core material and tried to improve the durability through nitriding treatment. The durability of the electrocatalyst was clearly influenced by controlling the nitriding level of Co. CoN@Pt/C was prepared by sonochemical reaction followed by nitriding treatment. Nitriding levels were controlled through pressure control (1, 40, 80 bar) during the ammonia heat treatment process. We confirmed that the active metal has a particle size of (3 - 4) nm and a Pt-skin structure, and confirmed the improved ORR activity over commercial Pt/C catalysts. Most importantly, we have achieved excellent durability when the nitriding level of Co is controlled high. In the accelerated stress test (AST), the electrocatalyst nitrided at the elevated pressure showed little change in ECSA and ORR. It’s confirmed that through the control of the nitriding level for low-cost transition metals, a highly durable Core-shell electrocatalyst can be successfully fabricated. Figure 1