Progress of carbon-based electrocatalysts for flexible zinc-air batteries in the past 5 years: recent strategies for design, synthesis and performance optimization

Abstract

The increasing popularity of wearable electronic devices has led to the rapid development of flexible energy conversion systems. Flexible rechargeable zinc-air batteries (ZABs) with high theoretical energy densities demonstrate significant potential as next-generation flexible energy devices that can be applied in wearable electronic products. The design of highly efficient and air-stable cathodes that can electrochemically catalyze both the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are highly desirable but challenging. Flexible carbon-based catalysts for ORR/OER catalysis can be broadly categorized into two types: (i) self-supporting catalysts based on the in situ modification of flexible substrates; (ii) non-self-supporting catalysts based on surface coatings of flexible substrates. Methods used to optimize the catalytic performance include doping with atoms and regulation of the electronic structure and coordination environment. This review summarizes the most recently proposed strategies for the synthesis of designer carbon-based electrocatalysts and the optimization of their electrocatalytic performances in air electrodes. And we significantly focus on the analysis of the inherent active sites and their electrocatalytic mechanisms when applied as flexible ZABs catalysts. The findings of this review can assist in the design of more valuable carbon-based air electrodes and their corresponding flexible ZABs for application in wearable electronic devices.

Double-Activator Modulation of Ultrahigh Surface Areas on Doped Carbon Catalysts Boosts the Primary Zn–Air Battery Performance

“…Recently, carbon-based metal-free electrocatalysts have gradually become cost-effective and promising alternatives to Pt-based electrocatalysts based on some advantages such as excellent electronic conductivity, corrosion resistance, high specific surface, and dimensional diversity. − As a result, the application of waste biomass materials, e.g., rice husk, pig blood, corn silk, and fish scales, to produce carbon materials is appreciated in virtue of waste utilization and cost savings. However, the internal electronic structure of pure carbon materials is relatively stable, which can result in inferior ORR catalytic activity.…”

Challenges for large scale applications of rechargeable Zn–air batteries

“…117 The main advantages of this form over transition metal sites are relatively simple fabrication, high yield, relatively stable performance, and the material itself has some catalytic activity. However, its own performance is not strong enough to support the use of high power, so many current studies combine it with transition metal sites for application, 122 which will be elaborated in a later section. In addition, doping other non-metallic elements such as N and S can significantly improve the electrochemical performance of carbon nanostructures.…”

Oxidation State Dependent Conjugation Controls Electrocatalytic Activity in a Two-Dimensional Di-Copper Metal–Organic Framework

“…Electrochemical devices can be operated using renewable energy sources and thus have become the main alternative to devices that rely on fossil fuel combustion . The need to use sustainable catalysts for the electrocatalytic key reactions, such as the reduction of oxygen and hydrogen, has led to enormous progress in the development of molecular and heterogeneous catalysts. − Specifically several carbon , and nonprecious transition-metal − containing molecular complexes have been developed that are capable of effectively catalyzing ORR and other reduction reactions. A general problem for these molecular complexes remains the heterogenization step.…”