Cobalt Phosphide Coupled with Heteroatom‐Doped Nanocarbon Hybrid Electroctalysts for Efficient, Long‐Life Rechargeable Zinc–Air Batteries

Abstract

Metal phosphides and heteroatom-doped carbons have been regarded as promising candidates as bifunctional catalysts for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). However, both have suffered from stability issues during repeated ORR and OER operations in zinc-air batteries (ZABs). Herein, this study reports a versatile cobalt-based hybrid catalyst with a 1D structure by integrating the metal-organic framework-derived conversion approach and an in situ crosslinking method. Among them, the 1D hybrid catalyst composed of ultrasmall cobalt phosphide nanoparticles supported by nitrogen-, sulfur-, phosphorus-doped carbon matrix shows remarkable bifunctional activity close to that of the benchmark precious-metal catalysts along with an excellent durability in the full potential range covering both the OER and ORR. The overall overpotential of the rechargeable ZABs can be greatly reduced with this bifunctional hybrid catalyst as an air-electrode, and the cycling stability outperforms the commercial Pt/C catalyst. It is revealed that the cobalt phosphide nanoparticles are in situ converted to cobalt oxide under the accelerated conditions during OER (and/or ORR) of the ZABs and reduces the anodic current applied to the carbon. This contributes to the stability of the carbon material and in maintaining the high initial catalytic properties of the hybrid catalyst.

Hierarchically Porous Multimetal‐Based Carbon Nanorod Hybrid as an Efficient Oxygen Catalyst for Rechargeable Zinc–Air Batteries

“…As expected, the whole spectrum shifted to higher binding energy after phosphidation process. Especially, the binding energies of metallic Co and oxidized Co species in FeNiCo@NC‐P shift to 778.4 and 781.0 eV, indicating the formation of Co‐P and Co‐PO x , respectively . Although the binding energy shift demonstrates the formation of CoP, the peak from FeNiCo@NC‐P at 778.4 eV only shifted 0.2 eV which establishes the existence of the mixture of metallic Co and CoP 22a,26.…”

“…Especially, the binding energies of metallic Co and oxidized Co species in FeNiCo@NC-P shift to 778.4 and 781.0 eV, indicating the formation of Co-P and Co-POx, respectively. [25] Adv. Funct.…”

Efficient Oxygen Reduction Catalysts of Porous Carbon Nanostructures Decorated with Transition Metal Species

“…However, the amount of the dopants will be decreased at extremely high temperature. To maintain a balance, a moderated pyrolysis temperature is required, which has been verified among the range of 700–1000 °C 13–15. Another vital parameter of the pyrolysis process is the carbonization atmosphere.…”

Gadolinium‐Induced Valence Structure Engineering for Enhanced Oxygen Electrocatalysis

“…Exploring non‐noble metal catalysts with desired activity and stability to replace costly Pt‐based ones for the oxygen reduction reaction (ORR) has been a significant challenge,4,5 for the large‐scale commercialization of energy‐related devices, such as rechargeable metal–air batteries6–9 and fuel cells 10,11. Transition metals and their derivatives, including alloys,12,13 oxides,14–16 chalcogenides,17–20 phosphides,21–23 carbides,24–26 and nitrides27–29 have attracted researcher's widely attention because of their intrinsic electrochemical properties and low price. Although the fact that these alternatives were proven effectively, their electrocatalytic performances for the ORR need to be further improved in comparison to that of Pt‐based catalysts, and are not satisfactory to meet the practical requirements.…”