Alkaline membrane fuel cells

Anion exchange membrane fuel cells (AEMFCs) or Alkaline membrane fuel cells (AMFCs) are alternative to Proton exchange membrane fuel cells (PEMFCs). Over the last decade, AMFCs have drawn a lot of interest due to the viable use of inexpensive platinum group metal-free catalysts for the oxygen reduction reaction (ORR), and much more facile ORR in alkaline media even with Pt catalysts. However, reported performance of most AMFCs was low, and the cause of the poor performance was unclear. Many studies point out the sluggish HOR reaction, low hydroxide conductivity and chemical stability of alkaline ionomer and membrane, and electrochemical instability of Pt catalysts at higher potential for lower AMFC performance and durability. Our group at LANL has carried out extensive work to solve these puzzling problems inherently present in AMFCs and are obstacle for commercialization of AMFCs. We found phenyl group adsorption as major limiting performance limiting factor and developed strategies to overcome focusing on alternative catalyst and ionomer system.

Redox flow batteries

The redox flow battery (RFB) is an important electrochemical energy storage device, which was realized in the 1970s. The RFB has an Ion exchange membrane (IEM) separating the positive and the negative electrolytes. During the charge/discharge cycles, the redox couples undergo electrochemical reduction and oxidation reactions. Simultaneously, the IEM allows the transport of charge carriers to maintain electroneutrality. Among the various RFBs, vanadium redox flow batteries (VRFBs) have attracted much attention due to the presence of the same metal cation in the catholyte and the anolyte solutions. Therefore, the crossover of the vanadium ions through the membrane is a reversible regeneration process, which provides a long life to the electrolyte solution. Despite the several advantages of the VRFBs such as long life, simple redox reactions, and independence from energy and power ratios, the application of this technology continues to be limited. A related disadvantage is the reliability issue that arises from the crossover of the active species through the IEM, which requires the periodic regeneration of the electrolytes in VRFBs. CEMs possess high permeability to vanadium ions, since the membranes are intrinsically permeable to cations along with the charge carrier protons. Hence, VRFBs assembled with CEMs show lower coulombic efficiency.