“Green Electricity” to “Green Hydrogen”: PEM Water Electrolysis for Hydrogen Production

Hydrogen production via water electrolysis refers to the dissociation of water molecules into oxygen and hydrogen gases under the action of direct current, with oxygen and hydrogen being released respectively from the anode and cathode of the electrolyzer. Depending on the membrane material used in the electrolyzer, this process can be categorized into three technological approaches: alkaline water electrolysis (AWE), proton exchange membrane (PEM) electrolysis, and solid oxide electrolysis cell (SOEC) electrolysis.

Alkaline (AWE) Water Electrolysis for Hydrogen Production

The diaphragm in alkaline water electrolysis hydrogen production cells is primarily composed of asbestos and serves to separate the gases. Alkaline water electrolysis boasts the largest scale and highest level of commercialization. Although it features a simple structure, mature technology, and low cost, it suffers from low efficiency and poor performance. Moreover, its asbestos diaphragm has drawbacks such as environmental pollution.

Solid Oxide Electrolysis Cell (SOEC) for Hydrogen Production via Water Electrolysis

Solid oxide electrolysis for hydrogen production uses solid oxides as the electrolyte material and operates at temperatures ranging from 800 to 1,000°C. This approach significantly enhances the electrochemical performance of the hydrogen production process, leading to higher efficiency. However, its high-temperature operating conditions and slow start-up time remain drawbacks that limit its application scenarios.

Proton Exchange Membrane (PEM) Water Electrolysis for Hydrogen Production

Proton exchange membranes with excellent chemical stability, proton conductivity, and gas separation properties are used as solid electrolytes in PEM water electrolysis for hydrogen production. These membranes effectively block electron transfer, thereby enhancing the safety of the electrolyzer.

Principle of Hydrogen Production via PEM Water Electrolysis

The main components of a PEM electrolyzer include the proton exchange membrane, anode and cathode catalyst layers, anode and cathode gas diffusion layers, and anode and cathode end plates. Among these, the gas diffusion layers, catalyst layers, and proton exchange membrane together form the membrane electrode assembly, which serves as the primary site for mass transport and electrochemical reactions within the entire water electrolyzer. The properties and structure of the membrane electrode directly influence the performance and lifespan of the PEM water electrolyzer.

Membrane electrode assembly

Advantages of PEM Water Electrolysis for Hydrogen Production:

1. Using pure water electrolysis avoids potential environmental pollution and is environmentally friendly.

2. The proton exchange membrane has low resistance and gas permeability, resulting in high current density, high efficiency, and high gas purity.

3. Fast dynamic response speed, adapting to the volatility of renewable energy generation.

Prospects for PEM Water Electrolysis Hydrogen Production:

PEM electrolysis for hydrogen production has now entered the commercial application stage and is being planned and implemented in numerous demonstration projects aimed at producing hydrogen from renewable energy sources. The number of demonstration projects and the scale of individual projects have been steadily increasing year by year, and in the future, this technology will play a crucial role in deep decarbonization across multiple sectors, including transportation, chemical industry, steelmaking, and energy storage.