Evaluation of zeolites-incorporated silver as bifunctional electrocatalysts for direct borohydride fuel cells
Three zeolites (A, X and Y) with Ag incorporated in their cages are tested as bifunctional electrocatalysts for a direct borohydride fuel cell (DBFC). Ag zeolites are characterised by XRD, FTIR, nitrogen sorption and SEM, as well as by electrochemical methods. AgY zeolite shows good activity for the anodic reaction, i.e., borohydride oxidation reaction (BOR) in alkaline media, presenting low onset potential and high current densities. BOR kinetic and faradaic parameters at AgY are calculated, with the number of exchanged electrons being 4.3. The BOR at AgY was found to be a first order reaction in respect to BH4- concentration with activation energy of 13 kJ mol 1. Regarding ORR, AgX shows the best performance with the highest current densities and good stability over time. A two-electron pathway is observed for ORR at AgX and specific capacitance was calculated to be 5.61 F g-1. The DBFC performance is investigated based on half-cell measurements of AgY anode and Pt/C cathode.