Candied Haws-Like Fe–N–C Catalysts with Broadened Carbon Interlayer Spacing for Efficient Zinc–Air Battery

Abstract

As efficient nonprecious metal catalysts for oxygen reduction reaction (ORR), Fe−N−C materials are one of the most promising alternatives to Pt-based catalysts for fuel cells and metal−air batteries. However, the intrinsically low density of key active sites like FeN 4 moieties hampers their commercial applications. Herein, we provide a smart strategy to construct a candied haws-like Fe−N−C catalyst (CH-FeNC) with broadened carbon interplanar spacing (>4 Å), starting with trehalose as a structure-built brick coupled with a zinc-zeolite imidazole framework (ZIF-8) and polyaniline (PANI) and then followed by copyrolysis carbonization of them. The obtained CH-FeNC exhibits half-wave potentials of 0.92 and 0.90 V (vs RHE) before and after 10,000 cycles in 0.1 M KOH, which are superior to the 0.90 and 0.85 V obtained by commercial Pt/C for ORR. The power density of a homemade zinc−air battery equipped with the catalyst is up to 131 mW cm −2 , greater than that of Pt/C (124 mW cm −2 ). The extended X-ray absorption fine structure (EXAFS) results and density functional theory (DFT) theoretical calculations reveal that there exists enriched zigzag or armchair edge-hosted FeN 4 active sites, located at the abundant interface between carbon components in this composite. Furthermore, the unique broadened carbon interlayer spacing plays a key role in deciding the ORR rate in alkaline but not in acidic environments because there exists a fifth ligand of active Fe in the form of FeN 4 centers coupled with SO 4 2− and ClO 4 − from acids.

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.…”