In operando electrochemical impedance spectroscopy monitoring of nickel catalysts for hydrogen production, Part I: Methodology and performance characterization

More than 75 % of today's H-2 production is based on reforming processes using heterogeneous catalysts. In addition, catalysts are needed for hydrogen generation from renewable resources such as biomass or biogas. However, no direct online monitoring of commercial Ni based catalysts is established. Catalysts are only monitored indirectly by measuring gas compositions, temperature profiles or using coke sensors, although direct online monitoring could detect degradation mechanisms at early stages. We demonstrate the methodology for electrochemical impedance spectroscopy based online monitoring of commercial Ni catalysts. Furthermore, we studied the impact of three different contacting methods of Ni catalysts with ohmic resistances between 10 omega and 105 omega after the heat up procedure on the measurement results. Monitoring of the heat up phase revealed, that choosing the right contacting method is essential to observe processes such as NiO reduction, whereas monitoring of degradation due to carbon loading was observed with every tested contacting method. The demonstrated online monitoring of catalysts could be used to find and maintain more efficient and stable reforming conditions. In addition, the gained knowledge could even be used to prolong the lifetime of catalysts by in situ adapting of operating conditions.

Automated summary

More than 75% of today's H-2 production is based on reforming processes using heterogeneous catalysts. However, there is no established direct online monitoring method for commercial Ni-based catalysts. This study demonstrates the use of electrochemical impedance spectroscopy for online monitoring of Ni catalysts and examines the impact of different contacting methods on measurement results.