Design of M-N/C Catalysts for Electrocatalytic Energy Conversion Reactions

Abstract

Development of highly active, durable, and low-cost electrocatalysts has been of pivotal importance for high-performance energy conversion devices. Transition metal (M) and nitrogen (N) co-doped carbon (M-N/C) catalysts have emerged as a promising class of nonprecious metal catalysts. The syntheses of M-N/C catalysts commonly involve a high-temperature pyrolysis step, which however unavoidably generate a heterogeneity of metallic sites: active M-N/C sites and less active M@C sites. We have recently developed the "silica-coating-mediated" synthesis of M-N/C catalysts that can modulate a relative density of these two types of sites. In an extreme case, we could generate a catalyst that comprise M-N/C sites exclusively. The developed catalysts could serve as model systems for identifying the active sites for energy conversion reactions, such as oxygen reduction reaction and hydrogen evolution reaction, and some of the catalysts showed excellent catalytic activity for these reactions.