Automated Production of Catalyst Coated Membranes for PEM Water Electrolysis Using a Direct Ultra-Sonic Spray Coating Approach

Abstract

The production of green hydrogen through polymer electrolyte water electrolysis (PEMWE) has attracted attention in recent years for its potential to enable the widespread use of green hydrogen [1, 2]. This technology particularly impacts important sectors of today’s society such as the agricultural and mobility sectors. Among the different components of an electrolysis cell, the membrane electrode assembly (MEA) is regarded as the most important component for its operation, since it is where the water-splitting reaction takes place. For this reason, the choice of materials and production approach play a highly important role to optimize its lifetime, performance, and cost [3]. Within this context, the MEA production via ultra-sonic spray coating has been lately gaining relevance due to its potential to yield high-activity electrode layers with a low catalyst loading.Conventionally, electrodes for PEMWE have been fabricated using other catalyst deposition techniques such as the doctor blade, airbrush spray coating or rod coating on a separate substrate, which is then transferred onto the membrane via hot pressing. However, the shortcomings of these approaches which include an additional hot press step were recently reported, particularly due to the complexity associated with electrodes with low catalyst loadings due to their sensitivity towards mechanical stress [1, 4]. On the other hand, effective approaches involving a direct ink deposition onto the membrane using ultra-sonic spray coating have been long reported for fuel cell applications [5, 6].In this work, we take the approach of direct ink deposition via ultra-sonic spray coating to produce iridium based MEAs for PEMWE. Furthermore, the dependency of the MEA electrochemical activity on the process and material choice are studied in an iterative manner. Of particular interest for this study is the material transfer rate from the catalyst ink to the membrane, the reproducibility of the developed spray coating process and the variation of materials used for the MEA fabrication. The spray process was performed with an ultra-sonic spray nozzle attached to an automized 3-axis rig and coupled with a syringe pump. The fabricated MEAs were characterized using a single cell setup with an active area of 4 cm2. The results of the first generation of the fabricated MEAs show that the material ratios in ink composition play an important role in the ink flowability through the piping which carries the ink to the ultra-sonic nozzle. Furthermore, this behavior has a direct and strong influence on the final composition of the catalyst layer, which consequently directly affects the cell performance.