Stability and durability of water electrolysers
A review of developments in water electrolysis for hydrogen production and the potential to increase efficiency and hydrogen production rates over longer lifetimes
Dr Sakthivel. S TATA Consulting Engineers Limited
C urrently, hydrogen production is around 70 Mtpa (million metric ton per annum) worldwide. Global hydrogen demand is projected to increase to more than 800 Mtpa by 2050, driven by actions to mitigate climate change via energy transition and the decarbonisation of industrial processes. India’s total hydrogen demand is likely to grow from 6.7 Mtpa in 2021 to 11.7 Mtpa by 2030 and 28 Mtpa by 2050 (India Government, 2021). Many countries have plans to increase electrolyser capacity to meet the growing demand for low- carbon-intensity hydrogen. The global electrolyser capacity is expected to increase from 0.3 GW in 2020 to about 16.7 GW by 2026 (IEA, 2021). In comparison with the global picture, India’s electrolyser manufacturing ecosystem is at a nascent stage. However, the levelised cost of green hydrogen remains high ($6-7 per kg) relative to fossil- based grey hydrogen ($1-2 per kg). A number of challenges need to be overcome to raise the technology maturity level for water electrolysis. These include a high capital requirement, relatively high specific energy consumption, and other technical challenges impacting electrolyser stability and durability. This article reviews the current understanding of cell and stack construction, electrolyser technology selection, and the effect of current density, electrodes, electrolyte, anode-cathode separator, and dynamic/variable load on the durability and stability of electrolyser cell and stack.
DC power
Oxygen receiver
Hydrogen receiver
e –
OH –
H
O
OH –
End plate
End plate
H + H +
Electrolyte
Electrolyte
Diaphragm
Anode (+)
Cathode (–)
Figure 1 Basic operation of alkaline water electrolysis
between electrodes and electrolyte in a cell when an electrical current is applied. A basic water electrolysis unit or cell consists of an anode, a cathode, a power supply, and an electrolyte, as shown in Figure 1 . The cell is composed of two electrodes (anode and cathode) immersed in a liquid electrolyte or adjacent to a solid electrolyte membrane, two porous transport layers (which facilitate the transport of reactants and removal of products), and the bipolar plates that provide mechanical support and distribute the flow. Typically, hydrogen and oxygen are produced from the decomposition of water by two half- reactions: the cathodic hydrogen evolution reaction (HER) and the anodic oxygen evolution
Chemistry of water electrolysis The electrochemical process takes place
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