Process Monitoring of PEM H2 Electrolysis Feed Water Using TOC-1000e

Significance of the Topic

The production of green hydrogen via PEM electrolysis is pivotal for decarbonizing industries and transportation. High‐purity feed water is essential to maintain stack performance, avoid membrane fouling, catalyst degradation, and ensure the economic viability of large‐scale hydrogen plants.

Objectives and Study Overview

This application note evaluates the Shimadzu TOC‐1000e online analyzer to monitor total organic carbon (TOC) and conductivity in the ultrapure water loop feeding a PEM electrolyzer. The goals are to demonstrate rapid detection of ionic and organic contaminants, support preventive maintenance, and validate system performance under continuous operation.

Methodology and Instrumentation

Water quality specifications for PEM stacks typically require TOC below 50 ppb, conductivity under 0.1 µS/cm, and resistivity above 10 MΩ·cm. Pre‐treatment (sand filtration, ultrafiltration, softening, reverse osmosis, electrodeionization) reduces bulk contaminants. A polishing stage using ion‐exchange resin delivers final ultrapure water.

Instrument:

• Shimadzu TOC‐1000e online TOC/conductivity analyzer
• Excimer UV lamp (172 nm) for mercury‐free oxidation
• Active-Path™ flow cell eliminating air pockets and minimizing carryover
• Vial sampler enabling on‐site annual calibration
• Modbus TCP connectivity and built‐in web server for remote diagnostics

Measurement cycle time is approximately 2.5 minutes, with differential conductivity detection for TOC and direct conductivity readings.

Key Results and Discussion

Continuous monitoring of ASTM Type 1 ultrapure water over two days demonstrated:

• Stable baseline TOC below 1 ppb
• Conductivity fluctuations within specification (0.04–0.08 µS/cm)
• Rapid detection of simulated contamination events before stack entry

Early warning capabilities allow operators to intervene in the water treatment chain, preventing irreversible stack damage. Comparison of pre‐treatment energy (7–9 kWh/m³ for seawater purification) with electrolyzer energy (≈5000 kWh/m³) highlights the relative efficiency and cost‐effectiveness of feed water quality control.

Benefits and Practical Applications

The TOC‐1000e enables:

• Real‐time assurance of ultrapure water quality
• Reduced downtime and maintenance costs for PEM stacks
• Flexible deployment across plant locations due to compact size (<3 kg)
• Enhanced data integration through digital communication protocols

This supports reliable green hydrogen production and optimizes overall plant performance.

Future Trends and Possible Applications

Future developments may include:

• Integration with AI‐driven predictive maintenance platforms
• Expanded sensor suites (e.g., dissolved oxygen, pH) for holistic water quality monitoring
• Application to other ultrapure water‐dependent industries such as semiconductor manufacturing and pharmaceutical QC
• Wireless data transmission and edge computing for remote installations

Conclusion

The Shimadzu TOC‐1000e offers a highly sensitive, fast, and portable solution for online monitoring of ultrapure water in PEM electrolysis. Its advanced UV oxidation technology and robust connectivity help safeguard electrolyzer performance, ensuring efficiency and longevity in green hydrogen production.

Reference

Shimadzu Corporation. Online TOC Analyzer TOC-1000e Application Note (05-SCA-130-612B-EN). First Edition September 2023, Revision B January 2025.