Preparation of “Co-N_x Carbon Net” Protected CoFe Alloy on Carbon Nanotubes as an Efficient Bifunctional Electrocatalyst in Zn-Air Batteries

Abstract

Herein, Co/Fe bimetallic hydroxide nanosheets (Co3Fe2 BMHs) were densely deposited on polypyrrole nanotubes (PPy NTs), followed by the successive coating of polydopamine (PDA) and zeolitic imidazolate frameworks (ZIF)-67 to form a composite catalyst precursor. Then, Co3Fe2 BMHs, PPy NTs, and ZIF-67/PDA in this precursor were calcined into Co2Fe alloy nanoparticles, nitrogen-doped carbon NTs (NCNTs), and a Co-N x activated carbon net, respectively, which constituted a novel composite catalyst. In this composite catalyst, the high-density Co2Fe alloy nanoparticles are highly dispersed on the NCNT and coated by the Co-N x activated carbon net. The Co-N x activated carbon net protects the alloy particles from agglomerating during calcination and from being corroded by the electrolyte. Moreover, the experimental results demonstrated that the calcination temperature and chemical components of the catalyst precursors greatly affect the morphology, structure, composition, and ultimately electrocatalytic activity of the calcined products. The obtained optimum catalyst material exhibited significant electrocatalytic effects on both the oxygen reduction reaction and oxygen evolution reaction with a small ΔE of 0.715 V. The Zn-air battery utilizing this material as the air electrode catalyst showed a power density of 235.5 mW cm–2, an energy density of 1073.5 Wh kg–1, and a round-trip efficiency of 62.3% after 1000 cycles, superior to the benchmark battery based on the mixed commercial catalyst of Pt/C and RuO2. An all-solid-state battery was also assembled to confirm the practical application prospect of the prepared composite material as the air electrode catalyst. More importantly, both experimental data and density functional theory calculations verified that the superior bifunctional catalytic activity was mainly attributed to the synergy between the Co-N x activated carbon net and Co2Fe alloy.

“Setaria viridis”-like cobalt complex derived Co/N-doped carbon nanotubes as efficient ORR/OER electrocatalysts for long-life rechargeable Zn–air batteries

“…, Pt/C). 11–15 The electrocatalytic activity of M–N–C is closely related to carbon scaffolds, such as the morphology ( i.e. , sphere, sheet, tube, fiber, etc .)…”

“…materials have attracted wide attention in electrocatalysis due to their comparable activity and superior durability to noble metal catalysts (i.e., Pt/C). [11][12][13][14][15] The electrocatalytic activity of M-N-C is closely related to carbon scaffolds, such as the morphology (i.e., sphere, sheet, tube, fiber, etc.) and structure (heteroatom-doping, graphitization, defects, etc.).…”

Polypyrrole Template-Assisted Synthesis of Tubular Fe-NC Nanostructure-Based Electrocatalysts for Efficient Oxygen Reduction Reaction in Rechargeable Zinc–Air Battery

“…Notably, zeolite imidazole frameworks (ZIFs) involving imidazole ligands and metal centers (Zn, Co, etc.) have been intentionally utilized as precursors/templates to construct the carbon-supported metal nanoparticles (NPs) or single atoms due to their merits such as high porosity, robust framework, and plentiful N-rich ligands. − Scientists have devoted considerable efforts to the syntheses and performances of ZIFs and their derivatives. − Based on the above considerations, it is expected that the calcination treatment of Fe-doped Zn-ZIF is able to not only achieve a high density of Fe-based active sites but also generate abundant hierarchical pores and structural defects induced by zinc evaporation in the process of pyrolysis, which facilitate significant enhancement of the ORR activity . Unfortunately, direct pyrolysis for ZIFs usually undergoes an inevitable self-aggregation, and severe morphological contraction and structural collapse, which is not conductive to boosting the catalytic performance .…”