Boosted charge transfer in oxygen vacancy-rich K+ birnessite MnO2 for water oxidation and zinc-ion batteries

Manganese Dioxide (MnO2) as an efficient cathode material for zinc-ions battery (ZIBs) and water oxidation has always been a research emphasis because of its rich crystal phases, tunnel and layered structure, which is conducive to the deintercalation / intercalation of zinc ions. However, the key bottleneck of MnO2 electrode materials are their poor rate capability and electrochemical stability. Herein, we successfully obtained oxygen vacancy-rich K-birnessite MnO2 (KxMnO2) by plasma etching strategy. K+ intercalation in MnO2 can adjust the interlayer distances, which improves the structural stability of material, and constructs a tunable Zn2+ channel. Meanwhile, the oxygen vacancy is not only contribute to the fast adsorption and diffusion of electrolytic ions, but also to the rapid transfer of charges. In addition, the nano-structure could provide abundant reaction sites and short diffusion pathways. Remarkably, the KxMnO2 is used cathode material of ZIBs after plasma optimization treatment presents reversible specific capacity of 272 mAh g(-1) at 1 mA cm(-2), and then it could reach an admirable capacity of 310 mAh g(-1) after 100 cycles. As the oxygen evolution reaction (OER) electrocatalysts, the overpotential to reach 10 mA cm(-2) of KxMnO2 is 1.47 V of versus RHE. The Tafel slope is 36 mV dec(-1), which is lower than that of the KxMnO2 without plasma treatment (244 mV dec(-1)). This study provides a new opportunity to design low-cost and high-performance electrode materials for rechargeable zinc-ion batteries and OER catalyst by using plasma processing technology. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

In this study, oxygen vacancy-rich K-birnessite MnO2 (KxMnO2) was successfully obtained through plasma processing, demonstrating improved structural stability and ion transport properties. This material can serve as a cathode material for zinc-ion batteries and an electrocatalyst for oxygen evolution reaction, offering a new opportunity for designing low-cost and high-performance electrode materials.