The water electrolysis test bench is a specialized experimental equipment used for researching, verifying, and optimizing the process of water electrolysis (including alkaline water electrolysis, proton exchange membrane water electrolysis, and other technologies). Its core working principle is based on the electrochemical nature of electrolyzed water, and it integrates multiple functional modules to achieve precise control, parameter monitoring, and performance evaluation of the electrolysis process. The following provides a detailed introduction from three aspects: core principles, key system components, and workflow:
1、 Core principle: Electrochemical reaction of electrolyzed water
The essence of water electrolysis is to drive water molecules (H ₂ O) to undergo reduction and oxidation reactions at the cathode and anode of the electrolytic cell under the drive of an external DC power source, decomposing them into hydrogen gas (H ₂) and oxygen gas (O ₂). The reaction equation is as follows:
Cathodic reaction (reduction reaction): Water molecules obtain electrons, generating hydrogen gas and hydroxide ions (alkaline conditions) or hydrogen ions (acidic/proton exchange membrane conditions).
Alkaline conditions: 2H ₂ O+2e ⁻ → H ₂ ↑+2OH ⁻
Proton exchange membrane (PEM) conditions: 2H ⁺+2e ⁻ → H ₂ ↑ (H ⁺ is produced by the decomposition of anode water and migrates to the cathode through the PEM)
Anodic reaction (oxidation reaction): Water molecules lose electrons and generate oxygen and hydrogen ions (or react with OH ⁻ to produce water).
Alkaline conditions: 4OH ⁻ -4e ⁻ → O ₂ ↑+2H ₂ O
PEM condition: 2H ₂ O-4e ⁻ → O ₂ ↑+4H ⁺
The above reaction requires overcoming the decomposition energy barrier of water molecules, so the test bench needs to provide sufficient electrolysis voltage through a DC stabilized voltage and current power supply (theoretical decomposition voltage is 1.23V, actual working voltage is usually 1.5-2.5V due to polarization, resistance and other losses). At the same time, the activation energy of the reaction is reduced by electrode materials (such as platinum and nickel on the cathode, iridium ruthenium oxide on the anode, etc.) to improve electrolysis efficiency.
2、 Key system composition and functions
The water electrolysis test bench is not a single device, but consists of an electrolysis cell module, an energy supply module, a fluid control module, a parameter monitoring module, and an auxiliary system. Each module works together to achieve controllability and measurability of the electrolysis process.
1. Electrolytic cell module (core reaction vessel)
The electrolytic cell is the core of the reaction, and its structure is designed according to testing requirements (such as alkaline, PEM, solid oxide water electrolysis, etc.), mainly including:
Negative/anode: using experimental target materials (such as new catalyst coated electrodes) to provide reaction sites;
Diaphragm/Electrolyte: Separate anode and cathode gases (prevent H ₂ and O ₂ from exploding), while conducting ions (such as the asbestos diaphragm in alkaline electrolysis cells conducting OH ⁻, and the proton exchange membrane in PEM electrolysis cells conducting H ⁺);
Flow channel: Design independent flow channels for water intake, hydrogen production, and oxygen production to ensure uniform fluid distribution.
2. Energy supply module (power source for driving reactions)
Usually used as a high-precision DC power supply, it can achieve two output modes of "constant voltage" and "constant current":
Constant voltage mode: Fixed electrolysis voltage, monitoring current changes (reflecting reaction rate and electrode activity);
Constant current mode: Fixed electrolysis current, monitoring voltage changes (reflecting system resistance and polarization degree).
Some high-end test benches also support electrochemical testing modes such as "linear sweep voltammetry" and "timed current/potential" for analyzing electrode kinetic characteristics.
3. Fluid control module (ensuring stable supply of reaction)
Responsible for providing stable deionized water (electrolyte solution) for the electrolytic cell and controlling fluid parameters:
Inlet system: Deionized water (with a purity of at least 18M Ω· cm to avoid impurities affecting electrode performance) is delivered through a precision peristaltic pump or plunger pump, and the flow rate can be precisely adjusted (usually 0.1-10mL/min);
Exhaust and Separation System: After the gas-liquid mixture generated by electrolysis is separated by a gas-liquid separator, the gas (H ₂, O ₂) is discharged through independent pipelines, and the liquid is refluxed or recycled;
Temperature control: The electrolytic cell is wrapped in a heating jacket and a constant temperature circulating water bath to control the reaction temperature within a set range (such as 25-80 ℃), and the effect of temperature on electrolysis efficiency is studied.
4. Parameter monitoring module (core for evaluating performance)
Real time collection of key parameters during the electrolysis process, used to calculate performance indicators such as electrolysis efficiency and energy consumption. The main monitoring parameters include:
Electrochemical parameters: Monitor electrolysis voltage, current, and impedance (EIS testing) through built-in sensors of the power supply or external electrochemical workstations;
Gas parameters: Measure the yield of H ₂ and O ₂ through gas flow meters (such as mass flow meters), and analyze the gas purity through gas chromatography (to detect the presence of trace amounts of O ₂ or H ₂);
Fluid and environmental parameters: Monitor the temperature and system pressure of the electrolytic cell through temperature sensors and pressure sensors, and monitor the purity of the incoming water through conductivity meters.
3、 Typical workflow
Taking the PEM water electrolysis test bench as an example, its standard workflow is as follows:
Preparation stage: Inject deionized water into the water tank, check the sealing and electrode connection status of the electrolytic cell, set the target temperature and inlet flow rate;
Startup and Stability: Turn on the constant temperature system and wait for the electrolytic cell temperature to reach the standard before starting the inlet pump to deliver water to the electrolytic cell; Turn on the DC power supply and preheat the system with low current/voltage for 5-10 minutes to eliminate bubbles in the flow channel;
Electrolysis and monitoring: Switch to the target working mode (such as constant current), and record real-time parameters such as voltage, gas yield, temperature, etc; If electrode performance needs to be studied, the electrochemical workstation can be started for linear scanning or impedance testing;
Data processing: Calculate core indicators based on monitoring data, such as "electrolysis efficiency" (the ratio of actual hydrogen production to theoretical hydrogen production), "specific energy consumption" (the amount of electricity consumed per unit volume of H ₂ produced, in kWh/Nm ³);
Shutdown phase: First, reduce the power output to zero and turn off the power; Stop the inlet pump, empty the residual water in the electrolytic cell, and blow the flow channel with nitrogen or dry air to prevent the electrodes from getting damp or the diaphragm from aging.