Anchoring Bimetal Single Atoms and Alloys on N-Doping-Carbon Nanofiber Networks for an Efficient Oxygen Reduction Reaction and Zinc–Air Batteries

Abstract

Electrocatalysts for the oxygen reduction reaction (ORR) play a central role in fuel cells and zinc–air batteries. Bimetal single atoms and nanoparticle hybrids are emerging ORR electrocatalysts, superior to the most exploited unary metal single-atom catalysts (SACs). Here, we report bimetal SAC-based nanofiber networks of Co3Fe7@Co/Fe-SAC for efficient ORR electrocatalysis and zinc–air batteries. A facile and easy-to-scale-up process is developed, and the versatility is validated in three hybrids. Strong electronic interaction is revealed between bimetal single atoms and alloy nanoparticles, leading to improved catalytic performances for ORR. Specifically, the Co3Fe7@Co/Fe-SAC hybrids exhibit a half-wave potential of 0.841 V in a basic electrolyte, comparable to the Pt/C electrocatalyst. Assembled in a zinc–air battery, a Co3Fe7@Co/Fe-SAC hybrid-based cell demonstrates a power density 1.8 times higher than the benchmark Pt/C-IrO2-based one, and it is stable for 150 cycles galvanostatic charge/discharge. The superior device performance is attributed to the appealing intrinsic activity, the carbon shielding effect for anti-leaching, and the hierarchical porous networks for large accessibility of active sites and favorable mass transport. Theoretical calculations suggest that alloy nanoparticles significantly improved the intrinsic catalytic activity of Fe single-atom sites at the expense of slightly lowering the activity of Co single-atom sites. This work presents a versatile process for the mass production of efficient composite electrocatalysts and highlights the power of bimetal single-atom-based hybrids and hierarchically porous structures for ORR device performances.

Understanding the mechanism and synergistic interaction of cobalt-based electrocatalysts containing nitrogen-doped carbon for 4 e− ORR

“…An accelerated durability test was performed to determine the stability of the catalyst and it was found that its current decayed by only 13 mV aer 10 000 cycles. 123 Yan Luo et al synthesized atomically distributed Fe and Co sites in nitrogen-doped carbon nanosheets (A-FeCo@NCNs) through a silica-modied strategy using ZIF-8 and ZIF-67. The synthesized SiO 2 @Fe-ZIF-8/67 was pyrolyzed at 800 °C for 2 h to obtain A-FeCo@NCNs.…”

“…An accelerated durability test was performed to determine the stability of the catalyst and it was found that its current decayed by only 13 mV after 10 000 cycles. 123…”

FeNiCrCoMn High-Entropy Alloy Nanoparticles Loaded on Carbon Nanotubes as Bifunctional Oxygen Catalysts for Rechargeable Zinc-Air Batteries

“…Rechargeable zinc-air batteries (ZABs) are highly preferred for their high specific energy density, security, and low contamination. − However, their commercial application is constrained by the inefficiency of oxygen conversion processes at the air electrode. − Currently, Pt-based catalysts are widely applied to oxygen reduction reaction (ORR). − The atomic layer deposition (ALD) method was used to put the Pt nanoparticle load on CNTs by Gan et al, which obtained a Pt/CNT catalyst with excellent ORR catalytic activity. Meanwhile, Ru or Ir-based catalysts are applied to oxygen evolution reaction (OER). ,− A highly universal wet-chemical approach was used to prepare RuO 2 nanowires (NWs) by Yang et al, which showed a lower OER overpotential under acidic and alkaline conditions.…”

Coupling Single-Ni-Atom with Ni–Co Alloy Nanoparticle for Synergistically Enhanced Oxygen Reduction Reaction

“…It is widely accepted that MN x sites are the main active sites for ORR, and the presence of metal nanoparticles (M-NPs) should be avoided for exposing maximally these active sites . Although some reports suggest that M-NPs encapsulated into few graphene layers can synergistically enhance the ORR. − Introducing adjacent metal centers, either in the form of MN x or M-NP, can modulate the electronic structure of M–N–C sites and expedite the ORR kinetics. − However, most of the reported studies are on the combination of SACs and M-NPs with the same metal types, and there are very rare reports which signify the synergistic coupling between SACs and M-NPs of different metal centers. This might be because of difficulty in achieving such active composite sites.…”