Advanced transition metal/nitrogen/carbon-based electrocatalysts for fuel cell applications

Abstract

The development of advanced transition metal/nitrogen/carbon-based (M/N/C) catalysts with high activity and extended durability for oxygen reduction reaction (ORR) is critical for platinum-group-metal (PGM) free fuel cells but still remains great challenging. In this review, we summarize the recent progress in two typical M/N/C catalysts (atomically dispersed metalnitrogen-carbon (M-N-C) catalysts and carbon-supported metal nanoparticles with N-doped carbon shells (M@NC)) with an emphasis on their potential applications in fuel cells. Starting with understanding the active sites in these two types of catalysts, the representative innovative strategies for enhancing their intrinsic activity and increasing the density of these sites are systematically introduced. The synergistic effects of M-N-C and M@NC are subsequently discussed for those M/N/C catalysts combining both of them. To translate the material-level catalyst performance into high-performance devices, we also include the recent progress in engineering the porous structure and durability of M/N/C catalysts towards efficient performance in fuel cell devices. From the viewpoint of industrial applications, the scale-up cost-effective synthesis of M/N/C catalysts has been lastly briefed. With this knowledge, the challenges and perspectives in designing advanced M/N/C catalysts for potential PGM-free fuel cells are proposed.

A review of carbon dots and their composite materials for electrochemical energy technologies

“…However, further improvements in the electrode materials used in these technologies are still needed, and new materials still need to be explored to reduce the cost and achieve even higher performance. In this regard, carbon‐based materials with different structures and morphologies have been explored and widely used in these electrochemical energy technologies due to their high abundance in nature, low cost, high conductivity, high chemical/thermal stabilities, high specific surface area, and so forth 1,2 …”

Atomically Dispersed Transition Metal-Nitrogen-Carbon Bifunctional Oxygen Electrocatalysts for Zinc-Air Batteries: Recent Advances and Future Perspectives

“…Based on pristine M-N-C catalyst, inserting secondary heteroatoms with a discrepancy in electron spin density and electronegativity can modulate the coordination environment and correspondingly alter electronic configurations of the M-N-C sites. Heteroatoms can also influence the catalytic activity of the M-N-C sites through the long-range delocalization and charge transfer effect, even if they cannot bind directly to the M-N-C sites [ 18 , 61 , 66 , 76 , 78 , 97 , 103 , 104 , 108 ]. Moreover, injecting heteroatoms into the electrocatalyst surface can significantly increase the density of active sites without severe structural collapse [ 12 ].…”

“…The metal center usually needs to cooperate with other atoms on the carrier to maintain stability. N-doped porous carbon as a carrier has a high specific surface area, abundant pores, and high N content, which is considered one of the most widely used substrates for stabilizing single metal atoms [74][75][76]. On the one hand, N is more electronegative and reactive than carbon, which makes the interactions between the metal and N atoms stronger [75].…”

Advanced Atomically Dispersed Metal–Nitrogen–Carbon Catalysts Toward Cathodic Oxygen Reduction in PEM Fuel Cells

“…ORR catalysts have been successfully prepared and investigated to replace commercial Pt/C catalysts. [ 29,59 ] Among them, atomic Fe‐embedded nitrogen‐doped carbon (Fe–N x /C) has received growing attention considering the high activity and stability. [ 38,60 ] Both experiments and DFT calculation disclosed that it is mainly the atomically dispersed Fe–N x species in nitrogen‐doped carbon that renders its high activity.…”