A Method for Oscillation-Free Dynamic IR Compensation During Potentiostatic Electrolyses.

Potentiostatic electrolysis is a widely used technique for evaluating the long-term performance of electrocatalysts in key electrochemical processes such as hydrogen and oxygen evolution, CO2 and nitrate reduction. However, accurate comparison of catalyst activity is often impaired by uncompensated solution resistance (IR drop), which causes a portion of the applied potential to be lost outside the electrode interface. This is especially problematic when the resistance varies dynamically during high-current experiments. In this study, a straightforward method is presented for achieving 100% dynamic IR compensation using commercially available Metrohm Autolab PGSTAT potentiostats. This approach is based on a continuous monitoring of the high-frequency resistance and direct current during electrolysis, and an adaptive digital setpoint adjustment to maintain a constant effective electrode potential. The applicability of the method is demonstrated through a case study on nitrate-to-ammonia reduction at high current densities, achieving stable operation without oscillations, even in cases where thermal effects and the related resistance decrease make the system prone to control instabilities. The method is described in detail, and free software and example code are provided to enable adoption by the broader electrocatalysis community.