Platinum group metal free (PGM-free) electrocatalysts represent an attractive low-cost alternative to PGM-based catalysts for several reactions of fundamental importance for electrochemical energy conversion and storage. Of various proposed PGM-free catalysts, the atomically dispersed transition metal-nitrogen-carbon (M-N-C, M = Fe, Co, Ni, or Cu, etc.) materials have been found to be especially promising for oxygen reduction reaction (ORR), as potential replacement for Pt-based cathode catalysts in low-temperature polymer electrolyte fuel cells (PEFCs), and more recently as catalysts for electrochemical reduction of carbon dioxide (CO₂RR). In this presentation, we will summarize recent progress in the development of M-N-C catalysts for these two important reactions.

The research effort in the development of M-N-C ORR electrocatalysts at Los Alamos dates back to early 2000s and has since yielded catalysts with substantially enhanced ORR activity and, lately, also with much improved durability [1-3]. Using advanced Fe‑N-C catalysts, we have achieved an activity of 38 mA/cm² at 0.90 V (iR-free) in an H₂-air PEFC, approaching the DOE 2025 current density target of 44 mA/cm². We have also demonstrated Fe-N-C catalysts with excellent durability, with no more than 30% loss of their initial activity at 0.70 V in a 600-hour PEFC test. Our Fe-N-C catalysts have also shown promise for anion exchange membrane fuel cells (AEMFCs), achieving 48 mA/cm² at 0.90 V (iR-free) and peak power density of 0.83 W/cm².

The development of sustainable carbon-neutral energy technologies to mitigate greenhouse gas emissions has become imperative and urgent. Of special interest and importance in this context is the use of electricity from intermittent renewable energy sources for electrochemical conversion of CO₂ to easily storable and transportable value-added products. Recently, M-N-C materials have emerged as promising CO₂RR catalysts thanks to their structure and high selectivity for certain reduction products, e.g., CO and HCOOH [4,5], though so far at lower current densities achieved with well-established Cu nanoparticle catalysts [6,7]. In this presentation, we will summarize our study of the activity, selectivity, and stability of M-N-C catalysts for CO₂RR in both an H-cell and at a rotating disk electrode (RDE). The CO₂RR activities have been improved by increasing metal loading, optimizing local M-N coordination environment, and enhancing metal-carbon substrate interactions. We will also demonstrate the impact of mass transport on performance of M-N-C catalysts in the H-cell and review methods of combatting the formation of hydrogen bubbles on stationary CO₂RR cathodes. Finally, we will discuss the use of M‑N-C catalysts in a tandem configuration to generate high energy-density CO₂RR products such as C₂H₄ and C₂H₃OH.