General Carbon-Supporting Strategy to Boost the Oxygen Reduction Activity of Zeolitic-Imidazolate-Framework-Derived Fe/N/Carbon Catalysts in Proton Exchange Membrane Fuel Cells

Bamboo-like nitrogen-doped carbon nanotubes directly grown from commercial carbon black for encapsulating FeCo nanoparticles as efficient oxygen reduction electrocatalysts

Efficient methods for preparing carbon nanotube (CNT)-confined metal catalysts are of great significance for electrocatalysis. Hence, in this study, Fe and Co promoters were added to the precursors of commercial carbon black and melamine to form N-doped CNTs confined bimetallic catalysts (FeCo@N-CNTs) via in situ pyrolysis. The FeCo@N-CNT catalysts exhibited a bamboo-like morphology with FeCo alloy nanoparticles encapsulated in the CNTs and high activity toward the oxygen reduction reaction, with a half-wave potential of 0.864 mV, higher than that of commercial Pt/C (0.827 mV) in alkaline solutions. The catalytic performance is attributable to the synergistic effects between the FeCo alloy and N-doped CNT structure. Moreover, the confinement of the FeCo nanoparticles inside the CNTs imparted the prepared catalysts with resistance to methanol poisoning and long-term stability. This versatile method of synthesizing CNTs directly from carbon black provides a new strategy for preparing high-performance non-precious-metal-based N-doped CNT catalysts for practical fuel cell applications.

Noble-Metal-Free FeMn-N-C Catalyst for Efficient Oxygen Reduction Reaction in Both Alkaline and Acidic Media

The oxygen reduction reaction (ORR) is important cathodic reaction running in several electrochemical energy conversion devices. It is still difficult to develop non-precious nanocatalysts for ORR that have high activity and increased durability for practical application. Herein, bimetallic FeMn(mIm)-N-C composite incorporated with Fe and Mn via an encapsulation-ligand exchange technique is prepared and established as an efficient ORR catalyst. The results reveal that FeMn(mIm)-N-C shows outstanding ORR performance with E_1/2 of 0.861 V and 0.778 V in alkaline and acid solutions, along with robust durability. Additionally, the assembled Zn-Air batteries (ZAB) and proton exchange membrane fuel cells (PEMFCs) both have exceptional power densities and show promise for long-term stability compared to 20% Pt/C. The present work provides a useful strategy for designing and synthesizing a reliable low-cost and high-efficient electrocatalysts for energy conversion and storage.