Eight-electron oxidation of borohydride at potentials negative to reversible hydrogen electrode

This is the first report of a novel anode catalyst, Pt/Ti2O, and its use for the complete 8-electron oxidation of borohydride without hydrogen evolution in a potential region negative to reversible hydrogen electrode (RHE). A major obstacle to the development of direct borohydride fuel cells (DBFC) has been the hydrogen evolution at the negative electrode, which causes low coulombic efficiency and safety problems. Attempts to prevent hydrogen evolution during the oxidation of borohydride on a fuel cell anode have always resulted in a shift of the anode potential to values more positive than the RHE potential, thus losing the advantages of DBFC in comparison to conventional hydrogen fuel cells. Pt supported on conductive titanium oxides (Ti2O) has been found to catalyze the 8-electron oxidation of borohydride without hydrogen evolution in a potential range more negative than RHE, which is desired in order to have a DBFC that is practically applicable. Mechanism of the direct 8-electron oxidation process is discussed on the basis of a synergistic effect at the surface of Pt/Ti2O catalyst.