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- ItemCovalent Organic Frameworks for Efficient Energy Electrocatalysis: Rational Design and Progress(Weinheim : Wiley-VCH, 2021) Zhang, Hua; Zhu, Minshen; Schmidt, Oliver G.; Chen, Shuillang; Zhang, KaiAn efficient catalyst with a precisely designed and predictable structure is highly desired to optimize its performance and understand the mechanism beyond the catalytic activity. Covalent organic frameworks (COFs), as an emerging class of framework materials linked by strong covalent bonds, simultaneously allow precise structure design with predictable synthesis and show advantages of large surface areas, tunable pore sizes, and unique molecular architectures. Although the research on COF‐based electrocatalysts is at an early age, significant progress has been made. Herein, the recent significant progress in the design and synthesis of COFs as highly efficient electrocatalysts for the oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER) is summarized. Design principles for COFs as efficient electrocatalysts are discussed by considering essential factors for catalyzing the OER, ORR, and HER processes at the molecular level. Herein, a summary on the in‐depth understanding of the catalytic mechanism and kinetics limitations of COFs provides a general instruction for further exploring their vast potential for designing highly efficient electrocatalysts.
- ItemAntifreezing Hydrogel with High Zinc Reversibility for Flexible and Durable Aqueous Batteries by Cooperative Hydrated Cations(Weinheim : Wiley-VCH, 2020) Zhu, Minshen; Wang, Xiaojie; Tang, Hongmei; Wang, Jiawei; Hao, Qi; Liu, Lixiang; Li, Yang; Zhang, Kai; Schmidt, Oliver G.Hydrogels are widely used in flexible aqueous batteries due to their liquid-like ion transportation abilities and solid-like mechanical properties. Their potential applications in flexible and wearable electronics introduce a fundamental challenge: how to lower the freezing point of hydrogels to preserve these merits without sacrificing hydrogels' basic advantages in low cost and high safety. Moreover, zinc as an ideal anode in aqueous batteries suffers from low reversibility because of the formation of insulative byproducts, which is mainly caused by hydrogen evolution via extensive hydration of zinc ions. This, in principle, requires the suppression of hydration, which induces an undesirable increase in the freezing point of hydrogels. Here, it is demonstrated that cooperatively hydrated cations, zinc and lithium ions in hydrogels, are very effective in addressing the above challenges. This simple but unique hydrogel not only enables a 98% capacity retention upon cooling down to −20 °C from room temperature but also allows a near 100% capacity retention with >99.5% Coulombic efficiency over 500 cycles at −20 °C. In addition, the strengthened mechanical properties of the hydrogel under subzero temperatures result in excellent durability under various harsh deformations after the freezing process. © 2019 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim