Mimicking Industrial Alkaline Water Electrolysis on a Laboratory Scale Using a Cost-Effective Beaker Cell Approach

Abstract

One of the most mature and promising processes for green hydrogen production is alkaline water electrolysis. Further efficiency improvements could be achieved by facilitating the sluggish oxygen evolution reaction (OER) with suitable anode materials. However, a major obstacle in research is that catalysts that are highly active on a laboratory scale do not automatically maintain their performance under industrially relevant conditions. The BMBF-funded project PrometH2eus sets out to find an advanced way of material development and performance evaluation. We strive to develop analytical techniques that mimic industrial conditions more realistically, but in a simple and reliable way, such that they are still applicable under conventional laboratory circumstances.In this work, a simplified and cost-effective beaker cell design was developed to research alkaline water electrolysis under industrially relevant conditions (30 wt.% KOH at 80°C). Initially, an investigation was conducted to determine which reference electrodes maintain their potential under these harsh conditions. Surprisingly, in addition to the state-of-the-art Hg/HgO electrode, a mini-RHE electrode revealed a very stable performance. Subsequently, the electrode integration of the working electrode into the system was systematically examined. As conventional electrode holders and contacting methods could not meet the special requirements of our setup, a new electrode holder was developed, that provides highly reproducible and stable measurements while being easy in handling. The developed set-up was shown to be suitable for operation under industrial conditions for more than 300 hours, at current densities of 1000 mA cm−2 using industrial benchmark electrodes, provided by project partner De Nora. No degradation was detected during the entire test period. Lastly, an electrochemical measurement protocol is recommended, designed to standardize electrode characterization, and thus provide comparable results between different laboratories in the developed setup. This protocol involves effective aging of the electrodes through accelerated stress tests and repeated activity measurements to determine the performance of the electrode as a function of the operating time. Figure 1: (a) CAD representation of the beaker cell setup including a heated stirring plate with an external PTFE-covered temperature sensor and an exhaust pipe for the evolving oxygen and hydrogen gas. Cross-section view of the beaker cell including a PTFE-beaker and -lid, the Hg/HgO reference electrode (RE), nickel mesh electrodes in the dimensions 1 x 1 cm² as the working electrode (WE), and 2 x 2.5 cm² as the counter electrode (CE). WE and CE are inserted using a self-designed nickel electrode holder. (b) Chronopotentiometry at 1000 mA cm-2 at 80°C in 30 wt.% KOH for 300 h using an industrial benchmark electrode (De Nora). Figure 1