Fabrication of bifunctional membrane electrode assemblies for unitised regenerative polymer electrolyte fuel cells

Abstract

Bifunctional membrane electrode assemblies have been fabricated using a screen printing technique, which demonstrate a repeatable and stable operation to cell current and voltages. This approach lends itself to a rapid, low-cost and repeatable fabrication process for bifunctional catalytic electrodes in polymer electrolyte membrane fuel cells and electrolysers.Introduction: The conversion and storage of energy with a high efficiency, especially a high specific energy, will be an important factor in future energy storage technologies. The relatively simple possibility to store hydrogen and oxygen with high specific energy combined with high energy conversion efficiency in fuel cells and electrolyser presents an opportunity for the use of polymer electrolyte membrane (PEM) unitised regenerative fuel cell systems (URFCs) as energy storage devices [1,2]. A URFC is an electrochemical cell working both as a fuel cell and as a water electrolyser (see Fig. 1).

Oxygen electrocatalysts for water electrolyzers and reversible fuel cells: status and perspective

“…However, due to slower kinetics and higher overpotential for OER at the oxygen electrode than cathodic processes concerning hydrogen evolution reaction at the hydrogen electrode, more effort has been devoted to the development and understanding of an efficient electrocatalyst for OER. [29][30][31][32][33][34] It has been reported that the platinum-based electrocatalyst is the most promising material for ORR over the entire range of pH, 21,[35][36][37][38][39][40] while it is ascribed as a poor OER electrocatalyst because the OER on the platinum surface needs a high overpotential (>300 mV). 41,42 Alternatively, metal oxides (e.g., ruthenium oxide and iridium oxide) have been extensively studied because they are highly active and stable in acidic media and have a wide anodic potential range.…”

“…[43][44][45] For the bifunctional oxygen electrode in RFCs, the electrocatalysts with a combination of platinum for ORR and metal oxide for OER have been proposed. 33,34,46 However, it has been pointed out that metal oxides are not thermodynamically stable under reducing conditions and conversely platinum is vulnerable to the oxidation by the oxidative species at high anodic potentials. 45,47 It is thus necessary to shed light on the subject of novel materials at the oxygen electrode which could improve electrocatalytic activity and tolerate rigorously oxidizing and reducing conditions during long-term operations in WEs and RFCs.…”

“…Bifunctional electrocatalysts for RFC applications have been developed using a combination of metallic platinum and OER electrocatalyst such as ruthenium (oxide) and iridium (oxide). 33,34 Dhar 108 first suggested a reversible fuel cell by fabricating a bifunctional oxygen electrode which consists of carbon backing, carbon-supported platinum, and iridium. Swette et al 30 prepared various bifunctional electrocatalysts and examined materials with single-layer and double-layer electrode architecture supported on a platinum-plated titanium mesh.…”

“…Recent studies on binary and ternary electrocatalysts in RFCs 34,46,110 have demonstrated that a pure ruthenium oxide at the oxygen electrode does not enhance the performance in RFCs. The reason may be related to different operating conditions between WE and RFC i.e., pure ruthenium oxide readily suffers from repeated operating mode conversions in RFCs, resulting in rapid losses of oxygen electrode property even with few potential swings, which is consistent with the results of Song et al 68 So, as mentioned before, the modifications of a pure ruthenium (oxide) electrocatalyst by alloying with transition metals or forming a core-shell structure that probably prevents underlying ruthenium (oxide) from oxidation and subsequent dissolution are worth noting in the future research.…”