利用膨胀网作为双极板流道结构优化碱性水电解槽

doi:10.61558/2993-074X.3469

摘要/Abstract

摘要：

碱性水电解制氢是现今最为成熟的水电解制氢技术。电解槽由多个电解小室组成，单个电解小室由隔膜、电极、双极板和端板等组成。现有工业的双极板流道结构为凹凸结构，通过模具冲压成型制备，制备成本高且困难。凹凸结构电解小室存在电解液流动不均匀和电流密度低的问题，进而增加了碱性水电解制氢的能耗和成本。因而，本文首先根据现有工业的凹凸双极板流道结构搭建电化学和流动模型，分析电解小室电流密度、电解液流动和气泡分布情况。模型可靠性已通过与文献实验数据对照验证。其中，电化学电流密度决定了气体产率，气体在电解液中流动反过来影响电化学反应活性比表面积和欧姆电阻。结果表明，凹凸结构电解小室凹球底部流动速度几近为零，凸球表面电解液流速较大，流道结构中存在旋涡，电解液分布不均。接着，建模优化碱性水电解槽的流道结构，比较了凹凸结构、网状、菱形和膨胀网结构电解小室电化学和流动性能。结果表明，膨胀网结构电解小室电流密度最大，为3330 A/m²，电解液流速最大，为0.507 m/s。相同电流密度下，过电位最小，能耗最低。本文对碱性水电解槽流道结构的全面理解和优化提供一定的指导意义，为大规模电解槽设计提供理论基础。

关键词: 碱性水电解槽, 膨胀网流道结构, 数值模拟

Abstract:

Alkaline water electrolysis (AWE) is the most mature technology for hydrogen production by water electrolysis. Alkaline water electrolyzer consists of multiple electrolysis cells, and a single cell consists of a diaphragm, electrodes, bipolar plates and end plates, etc. The existing industrial bipolar plate channel is concave-convex structure, which is manufactured by complicated and high-cost mold punching. This structure still results in uneven electrolyte flow and low current density in the electrolytic cell, further increasing in energy consumption and cost of AWE. Thereby, in this article, the electrochemical and flow model is firstly constructed, based on the existing industrial concave and convex flow channel structure of bipolar plate, to study the current density, electrolyte flow and bubble distribution in the electrolysis cell. The reliability of the model was verified by comparison with experimental data in literature. Among which, the electrochemical current density affects the bubble yield, on the other hand, the generated bubbles cover the electrode surface, affecting the active specific surface area and ohmic resistance, which in turn affects the electrochemical reaction. The result indicates that the flow velocity near the bottom of the concave ball approaches zero, while the flow velocity on the convex ball surface is significantly higher. Additionally, vortices are observed within the flow channel structure, leading to an uneven distribution of electrolyte. Next, modelling is used to optimize the bipolar plate structure of AWE by simulating the electrochemistry and fluid flow performances of four kinds of structures, namely, concave and convex, rhombus, wedge and expanded mesh, in the bipolar plate of alkaline water electrolyzer. The results show that the expanded mesh channel structure has the largest current density of 3330 A/m² and electrolyte flow velocity of 0.507 m/s in the electrolytic cell. Under the same current density, the electrolytic cell with the expanded mesh runner structure has the smallest potential and energy consumption. This work provides a useful guide for the comprehensive understanding and optimization of channel structures, and a theoretical basis for the design of large-scale electrolyzer.

Key words: Alkaline water electrolyzer, expanded mesh channel structure, Numerical simulation

熊海燕, 朱振啸, 高鑫, 范晨铭, 栾辉宝, 李冰. 利用膨胀网作为双极板流道结构优化碱性水电解槽[J]. 电化学（中英文）, 2024, 30(9): 2312281.

Hai-Yan Xiong, Zhen-Xiao Zhu, Xin Gao, Chen-Ming Fan, Hui-Bao Luan, Bing Li. Optimization of Channel Structure of Alkaline Water Electrolyzer by Using An Expanded Mesh as A Bipolar Plate[J]. Journal of Electrochemistry, 2024, 30(9): 2312281.

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链接本文: https://electrochem.xmu.edu.cn/CN/10.61558/2993-074X.3469

https://electrochem.xmu.edu.cn/CN/Y2024/V30/I9/2312281

图/表 17

Physical Field Parameter	Unit	Value
Electrolyte concentration	mol/L	6.72
Electrolyte conductivity	S/m	138
H₂ side exchange current density	A/m²	23.4
O₂ side exchange current density	A/m²	9.3
Exchange current density ( $α a$ , $α c$ )	/	0.5
Electrolytic cell voltage	V	2
Diaphragm conductivity	S/m	20.44
Electrolyte inlet flow velocity	m/s	0.22
Electrolyzer pressure	MPa	2
Operating temperature	°C	90

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	Geometric parameter	Value (mm)
	electrode radius Electrode height Diaphragm height Inlet length Inlet width Runner height Electrode height Diaphragm height Inlet length Inlet width Runner height	65
	electrode height	2
	diaphragm radius Electrode height Diaphragm height Inlet length Inlet width Runner height Electrode height Diaphragm height Inlet length Inlet width Runner height	65
	diaphragm height	0.7
	inlet length	6
	inlet width	6
	channel radius Electrode height Diaphragm height Inlet length Inlet width Runner height Electrode height Diaphragm height Inlet length Inlet width Runner height	65
	channel height	2
Single unit
concave-convex structure	Concave/ convex sphere radius	4.5
	concave and convex spheres distance	12
rhombus	height	2
	channel height	3
wedge	length	2.5
	width	1.25
	height	2.5
	channel height	3
expanded mesh	thickness	0.5
	height	2.33
	transverse distance	6
	longitudinal distance	4.23

Mesh type	Mesh 1	Mesh 2	Mesh 3	Mesh 4
Number of domain cell	14100	29466	102702	926090
Average cell mass	0.47	0.65	0.68	0.65
O2 current density	2449.5	2457.5	2459.8	2460.3
O2 Relative rate of change	0.44%	0.11%	0.02%	Baseline
Average flow velocity	0.00882	0.00900	0.00904	0.00922
Relative change rate	4.39%	2.39%	2.05%	Baseline