Origin of the Oxygen Reduction Activity on Boron-Doped Fe–N–C Catalysts for Zinc–Air Battery Applications

Abstract

Fe−N−C catalysts are considered promising alternatives to platinum-based oxygen reduction electrocatalysts in fuel cells and metal−air batteries. The oxygen reduction reaction (ORR) activity of the Fe−N−C catalysts was further improved by doping with electropositive boron, which outperformed the benchmark Pt/C catalysts. The boron-doped Fe−N−C catalyst was synthesized by two-step pyrolysis of a polyaniline (using FeCl 3 in boric acid) precursor, which exhibits superior ORR activity (E onset = 1.01 and E 1/2 = 0.88 V) with a turnover frequency of 3.86 Fe-sites −1 s −1 at 0.8 V. The mechanistic investigation of oxygen and H 2 O 2 reduction reaction on an Fe− N&B/C catalyst using kinetic analysis demonstrates that the ORR proceeds via a pseudo-4-electron pathway, wherein the boron sites catalyze the reduction of a H 2 O 2 intermediate. Furthermore, the poisoning experiments confirm the role of boron. Indeed, the stability of the Fe−N&B/C catalyst has improved due to the improved H 2 O 2 reduction kinetics on boron sites. Theoretical analysis supports the O 2 adsorption on boron sites with a relatively smaller activation barrier than the Fe sites. The Fe−N&B/C catalyst exhibits a superior power density (193 mW cm −2 ) and specific capacity (932 mA h g Zn −1) in a zinc−air liquid electrolyte battery. This analysis proves that the Fe−N&B/C materials could be the potential electrocatalytic materials for ORR while placing boron appropriately to induce the synergistic effect.

Potent Noble Metal–Nickel Oxide Interaction: A Strategy for Improved Oxygen Reduction Reaction via Engineering the Electronic Structure

“…Carbon neutrality has become a crucial subject due to the need for alternatives to fossil fuels to address global warming and environmental damage. , Fuel cells (FCs) and rechargeable metal-air batteries (MABs) are essential components of the renewable energy system due to their exceptional efficiency, high power density, dependability, and environmentally beneficial nature. , Both the FCs and MABs share the cathodic reaction of oxygen reduction reaction (ORR), which is a crucial reaction that determines the rate due to its slow kinetics . Hence, creating highly efficient ORR electrocatalysts is crucial for their broad use.…”