Hydrogel-Derived Co₃ZnC/Co Nanoparticles with Heterojunctions Supported on N-Doped Porous Carbon and Carbon Nanotubes for the Highly Efficient Oxygen Reduction Reaction in Zn–Air Batteries

Abstract

It is crucial for metal–air batteries and fuel cells to design non-precious-metal catalysts instead of platinum-based materials to boost the sluggish oxygen reduction reaction (ORR). Herein, Co3ZnC/Co nanoparticles with heterojunctions supported on N-doped porous carbon and carbon nanotubes (CNTs) are fabricated by pyrolyzing the hydrogel prepared from melamine and citric acid chelated with Co2+/Zn2+ ions. This hybrid shows strong ORR catalytic activity as its half-wave potential reaches 0.88 V (vs reversible hydrogen electrode (RHE)) in 0.1 M KOH and Zn–air batteries with the catalyst have higher discharge plateaus and capacity than those employing Pt/C. The hybrid mixed with RuO2 can also be used as an efficient bifunctional catalyst for rechargeable Zn–air batteries. The excellent performance is primarily derived from the Co3ZnC/Co heterojunctions, the electron transfer of which boosts the ORR catalysis. Moreover, the suitable ratio of Co/Zn in precursors results in the epitaxial growth of hollow CNTs and abundant mesopores, hence promoting the adsorption of oxygen and the transport of ORR-related species.

Co/CoO heterojunction rich in oxygen vacancies introduced by O2 plasma embedded in mesoporous walls of carbon nanoboxes covered with carbon nanotubes for rechargeable zinc–air battery

“…The bigger the I D /I G value, the more defects it indicates, which is beneficial for catalyst performance improvement. 28 The I D /I G for the P-Co/CoO V @NHCNB@NCNT is 1.15, which is higher than that of the Co@NHCNB@NCNT (0.93), indicating that the O 2 plasma treatment contributes to the creation of defects. Apparently, Raman spectra of the P-Co/CoO V @NHCNB@NCNT show the E g (474 cm −1 ), F 2g (515 cm −1 ), and A 1g (675 cm −1 ) vibrational modes of Co NPs.…”

“…The survey spectrum of P-Co/ CoO V @NHCNB@NCNT clearly manifests the coexistence of C, N, O, and Co elements (Figure S4A), which is in accordance with the EDX elemental mappings results (Figure 1H). The high-resolution X-ray photoelectron spectroscopy (XPS) spectrum of C 1s can be deconvoluted into four peaks (Figure 2B), corresponding to C═C/C-C (284.8 eV), C-O&C═N (285.6 eV), C═O&C-N (286.8 eV), and O-C═O (289.0 eV), 28 and the presence of C-N/C═N verifies that the nitrogen atom has been successfully incorporated into the carbon skeleton. The C═C/C-C occupies the highest proportion among all the components, revealing that the P-Co/CoO V @NHCNB@NCNT is mainly a graphite structure and thus it has high conductivity.…”

“…26,27 The effect of heterojunctions on improving the performance of bifunctional catalysts has been demonstrated in theory and experiments. 28,29 Specifically, strong electron coupling interaction occurs between different components of the heterojunctions multiphase structure, which will optimize the electronic structure, lower the reaction energy barrier, improve the binding capacity of the catalysts to interact with reaction intermediates, and promote the chemisorption of highly reactive species onto the catalyst surface, thus resulting in a significant increase in bifunctional catalytic activity. [30][31][32] In addition, introducing a large quantity of oxygen vacancies can further increase the number of active sites and the density of states (DOS) near the Fermi level, reduce the charge transfer resistance, and accelerate electron transfer, thus enhancing the reaction kinetic process.…”

Toward the Long-Term Stability of Cobalt Benzoate Confined Highly Dispersed PtCo Alloy Supported on a Nitrogen-Doped Carbon Nanosheet/Fe3C Nanoparticle Hybrid as a Multifunctional Catalyst for Zinc-Air Batteries

“…9 The Co 3 ZnC/Co nanoparticle heterojunctions created by Wang et al possessed high ORR electrocatalytic activity. 10 Li et al developed an asymmetric-NiFe cathode for high-activity ZABs. 11 However, the catalytic activity of transition metal-based electrocatalysts to OER and ORR is low and single, and it is difficult to drive OER and ORR simultaneously.…”

“…The development of sustainable energy is necessary to the rapidly growing global energy demand. , As new energy devices, direct alcohol fuel cells and zinc-air batteries (ZABs) are considered to be a pollution-free, renewable energy storage and conversion equipment owing to their high theoretical energy density as well as intrinsic safety. , The development of high-performance multifunctional catalysts for direct methanol oxidation reaction (MOR), oxygen reduction reaction (ORR), and oxygen evolution reaction (OER) remains a grand challenge in realizing fuel-cell vehicle applications and fixed power plants. − For example, Zhu et al constructed the porous carbon layers wrapped CoFe alloy with remarkably enhanced electrocatalytic efficiency for ORR and OER, which delivered distinguished durability in the 20,000 charging–discharging cycles . The Co 3 ZnC/Co nanoparticle heterojunctions created by Wang et al possessed high ORR electrocatalytic activity . Li et al developed an asymmetric-NiFe cathode for high-activity ZABs .…”