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

Abstract

An efficient and stable bifunctional oxygen catalyst is necessary to complete the application of the rechargeable zincair battery. Herein, an economical and convenient process was adopted to successfully coat high-entropy alloy Fe 12 Ni 23 Cr 10 Co 55−x Mn x nanoparticles on carbon nanotubes (CNTs). In 0.1 M KOH solution, with a bifunctional oxygen overpotential (ΔE) of only 0.7 V, the catalyst Fe 12 Ni 23 Cr 10 Co 30 Mn 25 /CNT exhibits excellent bifunctional oxygen catalytic performance, exceeding most catalysts reported so far. In addition, the air electrode assembled with this catalyst exhibits high specific capacity (760 mA h g −1 ) and energy density (865.5 W h kg −1 ) in a liquid zinc-air battery, with a long-term cycle stability over 256 h. The density functional theory calculation points out that changing the atomic ratio of Co/Mn can change the adsorption energy of the oxygen intermediate (*OOH), which allows the ORR catalytic process to be accelerated in the alkaline environment, thereby increasing the ORR catalytic activity. This article has important implications for the progress of commercially available bifunctional oxygen catalysts and their applications in zinc-air batteries.

Joule-Heating-Driven Synthesis of a Honeycomb-Like Porous Carbon Nanofiber/High Entropy Alloy Composite as an Ultralightweight Electromagnetic Wave Absorber

“…31 The results of Mn 2p resolution show that Mn exhibits two valence states in the material, including metallic (Mn 0 , 636.5 eV) and the oxidation states (Mn 2+ , 641.5 and 652.7 eV) of +2 valence. 44 The XPS results indicate that all metallic elements exist in the metallic and oxidation states. The former is from the intrinsic state of the HEA, while oxidation states may be due to partial oxidation caused by the high surface energy of the nanoparticles, resulting in different oxidation states for each element.…”

“…As for the Cu 2p spectra, the peaks at 932.8, 952.8, and 935.2 eV can be attributed to Cu 0 and Cu 2+ , respectively . The results of Mn 2p resolution show that Mn exhibits two valence states in the material, including metallic (Mn 0 , 636.5 eV) and the oxidation states (Mn 2+ , 641.5 and 652.7 eV) of +2 valence . The XPS results indicate that all metallic elements exist in the metallic and oxidation states.…”

“…The XPS results indicate that all metallic elements exist in the metallic and oxidation states. The former is from the intrinsic state of the HEA, while oxidation states may be due to partial oxidation caused by the high surface energy of the nanoparticles, resulting in different oxidation states for each element . The low magnification STEM elemental distribution maps (Figure S6) show that the oxygen element is predominantly distributed at the periphery of the HEA nanoparticle.…”

Synthesis of metallic high-entropy alloy nanoparticles

“…HEA nanoparticles of Fe 12 Ni 23 Cr 10 Co 55Àx Mn x with tunable Co/Mn ratios were also synthesized using NaBH 4 as a reducing agent and carbon nanotubes as support substrates. 16 The FeNiCrCoMn/C composites were annealed at 900 1C in a reducing atmosphere, forming a bifunctional oxygen catalyst for rechargeable zincair batteries. Singh and Srivastava applied lithium triethyl borohydride (LiEt 3 BH, or superhydride) to reduce metal chlorides (i.e., CrCl 2 , CoCl 2 , FeCl 2 , NiCl 2 , and CuCl 2 ) in benzyl ether at the boiling temperature to synthesize NiFeCrCuCo HEA nanoparticles.…”

“…Although the thermodynamic term ''high entropy'' is always highlighted in HEAs and related research, the success of synthesizing HEAs heavily relies on kinetics control over mixing atoms of different elements, crystallizing the homogeneously mixed atoms, and minimizing the diffusion of atoms in HEAs to avoid phase segregation. In the past five years, HEA research has predominantly focused on This journal is © The Royal Society of Chemistry 2024 synthesizing HEA nanoparticles and exploring their applications in energy-related fields, including catalysis, [6][7][8][9][10][11][12][13][14][15] electrochemical energy storage, 11,[16][17][18][19][20] and light harvesting and conversion. [21][22][23][24][25][26] The emergence of HEA nanomaterials and their promising properties have attracted extensive attention and resulted in some review articles primarily focused on catalysis.…”