Wang Rui, Sheng Hongyuan, Wang Fengmei, Li Wenjie, Roberts David S, Jin Song
Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, Wisconsin 53706, United States.
CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, National Center for Nanoscience and Technology, Beijing 100190, P. R. China.
ACS Cent Sci. 2021 Dec 22;7(12):2083-2091. doi: 10.1021/acscentsci.1c01157. Epub 2021 Dec 4.
Challenges posed by the sacrificial auxiliary reactions and expensive ion-exchange membranes in conventional electrosynthesis necessitate developing new electrochemical processes to enable efficient and sustainable distributed electrochemical manufacturing. Modular electrochemical synthesis (ModES) using a redox reservoir (RR) offers a promising membrane-free approach to improve energy efficiency and reduce waste through the pairing of multiple independent oxidative and reductive half-reactions; however, undesired ion-imbalance and induced pH changes in the existing ModES process limit sustained production. Here we present Ni(OH) as a heterogeneous RR that can selectively store and transport the hydroxide ions involved in the target half-reactions by reversible conversion with NiOOH to enable an ion-balanced ModES of two common disinfectants, hydrogen peroxide (HO) and sodium hypochlorite (NaClO). This hydroxide-balanced ModES realizes stable operation without appreciable pH swing to accumulate practically useful concentrations of HO and NaClO up to 251 and 481 ppm, respectively. These results illustrate additional design principles for electrosynthesis without sacrificial auxiliary reactions and the need for ion-selective RRs for modular electrochemical manufacturing.
传统电合成中牺牲性辅助反应和昂贵离子交换膜带来的挑战，使得开发新的电化学工艺以实现高效且可持续的分布式电化学制造成为必要。使用氧化还原储库（RR）的模块化电化学合成（ModES）提供了一种有前景的无膜方法，通过将多个独立的氧化和还原半反应配对来提高能源效率并减少废物；然而，现有ModES工艺中不希望出现的离子失衡和诱导的pH变化限制了持续生产。在此，我们展示了Ni(OH)作为一种非均相RR，它可以通过与NiOOH的可逆转化选择性地存储和传输目标半反应中涉及的氢氧根离子，从而实现两种常见消毒剂过氧化氢（HO）和次氯酸钠（NaClO）的离子平衡ModES。这种氢氧根平衡的ModES实现了稳定运行，pH几乎没有明显波动，分别积累了高达251 ppm和481 ppm的实际有用浓度的HO和NaClO。这些结果说明了无牺牲性辅助反应的电合成的额外设计原则，以及模块化电化学制造中对离子选择性RR的需求。
