An Oxygen‐Vacancy‐Rich Semiconductor‐Supported Bifunctional Catalyst for Efficient and Stable Zinc–Air Batteries

Abstract

The practical application of rechargeable zinc-air batteries requires a low-cost, efficient, and stable air electrode catalyst toward both the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). The most promising nonprecious bifunctional catalysts are carbon-supported transition metal hybrid materials. [1] However, carbon-supported catalysts suffer from carbon electrochemical oxidation, which causes the loss or aggregation of supported catalysts and degrades the electrocatalysis durability and performance. [2] To alleviate this problem, some strategies have been reported including coating the carbon support with corrosionresistive TiO 2 , [3] using conductive TiN as an alternative support, [4] or developing perovskite oxides as active catalysts. [5] However, both TiO 2 and perovskite oxides have an intrinsic low-conductivity drawback, and nor TiN is an optimum support material to obtain highly dispersed and active catalysts due to the nondefective surface structure. Thus, the objective of this study is to develop a conductive and oxidation-resistant support to relieve catalyst degradation, and at the same time achieve a high bifunctional catalytic activity with enhanced durability performance.Here, we propose that OV-rich, low-bandgap oxide semiconductor can be a promising support to design active and durable ultrafine metal catalysts in electrocatalysis (Figure 1a). This argument is built on our multidisciplinary understanding of OVs in semiconductor physics and heterogeneous solid-gas catalysis: i) the OVs lower the bandgap in oxide semiconductors: the higher the OV concentration, the higher the conductivity of the oxides [6] ; ii) in solid-gas catalysis, the OVs on oxide supports would provide a strong metal-support interaction (SMSI) with the supported metal catalysts and results in high metal dispersion, small metal size, high relative catalytic activity, and high stability. [7] That is, the OVs are not only beneficial for the conductivity of the oxides, but also offer an SMSI that favors the formation and stabilization of highly active ultrafine metal nanoparticles. Note that, in electrocatalysis, the role of OVs in metal oxides as active components is well reported for contributing to its enhanced catalytic activities. [8] However, the The highly oxidative operating conditions of rechargeable zinc-air batteries causes significant carbon-support corrosion of bifunctional oxygen electrocatalysts. Here, a new strategy for the catalyst support design focusing on oxygen vacancy (OV)-rich, low-bandgap semiconductor is proposed. The OVs promote the electrical conductivity of the oxide support, and at the same time offer a strong metal-support interaction (SMSI), which enables the catalysts to have small metal size, high catalytic activity, and high stability. The strategy is demonstrated by successfully synthesizing ultrafine Co-metaldecorated 3D ordered macroporous titanium oxynitride (3DOM-Co@TiO x N y ). The 3DOM-Co@TiO x N y catalyst exhibits comparable activities for oxygen reduction...

Multidimensional Ordered Bifunctional Air Electrode Enables Flash Reactants Shuttling for High‐Energy Flexible Zn‐Air Batteries

“…The C dl was calculated from double-layer charging curves in a non-faradic potential range of 1.1-1.3 V (versus RHE) and using the following equation in which i c and ʋ are charging current (mA cm −2 ) and scan rate (mV s −1 ), respectively [6][7][8][9][10] : The electrocatalytic performances for ORR and OER reactions were measured in a three-electrode cell at standard temperature and pressure conditions.…”

“…The MPZ battery provides an open circuit voltage (OCV) of 1.47 V that is higher than PI battery (1.35 V) and PZ battery (1.37 V, Figure 5b), indicating lower catalytic activation loss. 2019, 9,1900911 evidencing the fast kinetics of oxygen reactions. Some turbulences are observed in the polarization curve during charging due to vigorous oxygen bubble coa lescence at high current densities.…”

“…2019, 9,1900911 The practical application of rechargeable FZABs requires excellent electrochemical stability, which is examined by chron oamperometric (CA) measurements. Energy Mater.…”

Defect Engineering on Electrode Materials for Rechargeable Batteries

“…Thus, owing to the oxygen vacancies and the unique structure design, the catalyst achieved excellent electrochemical performance in Zn–air batteries. In addition, Chen and co‐workers reported that the oxygen vacancy defects can not only improve the conductivity of the oxide supports but also provide a stronger metal–support interaction (SMSI), so that the catalyst has a smaller metal size, higher catalytic activity, and higher stability for Zn–air batteries . Chou et al prepared CaMnO 3 nanotubes with abundant oxygen vacancies through calcination and sulfurization treatment.…”

Hierarchically Porous Co/CoxMy (M = P, N) as an Efficient Mott–Schottky Electrocatalyst for Oxygen Evolution in Rechargeable Zn–Air Batteries

“…Oxygen evolution reaction (OER: 4OH − → O 2 + 2H 2 O + 4e − ) has received wide attention recently because of its vital role in renewable energy devices, such as rechargeable Zn–air batteries and Li–O 2 batteries . An effective electrocatalyst is a necessity during the OER because it involves a stepwise four‐electron transfer at a high overpotential .…”