Technical Electrocatalysis for PEM Electrolyzers: Addressing the Challenges of High Activity, Stability and Cost Effectiveness

Kurzfassung

Proton exchange membrane (PEM) water electrolysis (EL) is considered as one of the most promising technologies for hydrogen production from renewable energies, which has a potential to penetrate the market in near future and enable the Power-to-Gas (P2G) application on a wider scale. However, reducing capital cost of PEM electrolyzers without losing efficiency is one of its most pressing challenges. Detailed cost analysis has shown that under future scenarios with high share of renewables, limited operation of 2000-3000 h per annum electricity (OPEX) and investment cost (CAPEX) are of equal importance for P2G plants. A recent study funded by FCH-JU demonstrates that the CAPEX of PEMEL stacks – which however depends on the specific stack design – are dominated by the cost of bipolar plates. In addition also current collectors contribute also significantly to the cost of the stack whereas the catalysts are presently of minor importance. Nevertheless, there is a wide perception that the anode catalysts may be the real hindrance for this technology. One reason is the sluggish oxygen evolution reaction (OER) kinetics on most electrocatalysts and their insufficient durability due to the highly corrosive working environment. To date, Ir-based catalyst is still the only feasible option to promote OER in the anode of a PEM electrolyzer due to its high activity and considerable stability. Still, the most often used catalysts are stable but nor very active rutile IrO2. Not only the high cost of the precious metal, but also the scarcity of Ir in the earth crust are barriers on the road to commercialization of PEM electrolyzers. Therefore, highly active and stable OER catalysts in acid electrolyte with ultra-low Ir loading are required to address this issue. In the introduction the current state of the art and the work addressing cost reduction for bipolar plates and current collectors will be shortly addressed. After that the work specifically on electrocatalyst development will be presented.