气候变化领域集成服务门户(CCPortal): In situ observation of pH change during water splitting in neutral pH conditions: Impact of natural convection driven by buoyancy effects

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DOI	10.1039/d0ee01760d
	In situ observation of pH change during water splitting in neutral pH conditions: Impact of natural convection driven by buoyancy effects
	Obata K.; Van De Krol R.; Schwarze M.; Schomäcker R.; Abdi F.F.
发表日期	2020
ISSN	17545692
起始页码	5104
结束页码	5116
卷号	13 期号:12
英文摘要	Photoelectrochemical water splitting in near-neutral pH conditions offers a safe and sustainable way to produce solar fuels, but operation at near-neutral pH is challenging because of the added concentration overpotentials due to mass-transport limitations of protons and hydroxide ions. Understanding the extent of this limitation is essential in designing a highly efficient solar fuel conversion device. In the present study, the local pH between the anode and cathode in a water splitting cell is monitored in situ using fluorescence pH sensor foils. By this direct visualization, we confirm that supporting buffer ions effectively suppress local pH changes, and we show that electrochemical reactions induce natural electrolyte convection in a non-stirred cell. The observed electrolyte convection at low current densities (<2 mA cm-2) originates from buoyancy effects due to the change in the local electrolyte density by ion depletion and accumulation. A multiphysics simulation that includes the buoyancy effect reveals that natural convection driven by electrochemical reactions stabilizes the local pH, which is consistent with our experimental observations. In contrast, the model without the buoyancy effect predicts significant shifts of the local pH away from the pKa of the buffer, even at low current densities. This experimentally validated model reveals that natural convection induced by electrochemical reactions significantly affects the overall mass-transport, especially in close vicinity of the electrodes, and it should, therefore, be considered in the design and evaluation of solar fuel conversion devices. This journal is © The Royal Society of Chemistry.
英文关键词	Buoyancy; Electrodes; Electrolytes; Fuels; Ions; Natural convection; pH sensors; Design and evaluations; Direct visualization; Electrochemical reactions; Electrolyte convection; In-situ observations; Mass transport limitation; Multiphysics simulations; Photoelectrochemical water splitting; pH effects; buoyancy; convection; in situ measurement; observational method; pH; water treatment
语种	英语
来源期刊	Energy & Environmental Science
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/189450
作者单位	Institute for Solar Fuels, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Hahn-Meitner-Platz 1, Berlin, 14109, Germany; Technische Universität Berlin, Department of Chemistry, Straße des 17. Juni 124, Berlin, 10623, Germany; Technische Universität Berlin, Department of Process Engineering, Straße des 17. Juni 135, Berlin, 10623, Germany
推荐引用方式 GB/T 7714	Obata K.,Van De Krol R.,Schwarze M.,et al. In situ observation of pH change during water splitting in neutral pH conditions: Impact of natural convection driven by buoyancy effects[J],2020,13(12).
APA	Obata K.,Van De Krol R.,Schwarze M.,Schomäcker R.,&Abdi F.F..(2020).In situ observation of pH change during water splitting in neutral pH conditions: Impact of natural convection driven by buoyancy effects.Energy & Environmental Science,13(12).
MLA	Obata K.,et al."In situ observation of pH change during water splitting in neutral pH conditions: Impact of natural convection driven by buoyancy effects".Energy & Environmental Science 13.12(2020).