Direct borohydride fuel cells: A selected review of their reaction mechanisms, electrocatalysts, and influence of operating parameters on their performance

Direct borohydride fuel cells (DBFC) oxidize an easily-stored energy-dense (sodium borohydride: NaBH4), that in theory reacts ca. 400 mV below H2 and produces 8 electrons per BH4- anion. However, the oxidation reaction (BOR) does not fully meet these promises practice: electrocatalyst nature, structure state-of-surface, operating conditions (pH, concentration, temperature, fluxes) noticeably influence BOR kinetics mechanism. Nickel platinum-based catalysts both have assets for BOR. DBFCs can only yield decent performance if their separator combines high ion-conductivity efficient separation of reactants; cation-exchange membranes, anion-exchange bipolar membranes porous separators all own advantages drawbacks. Besides anode, choice must consider DBFC cathode reaction, where oxygen (usually from air) or hydrogen peroxide are reduced, provided adapted used. All aspects drive stability/durability.