Transition-metal borides MB0.5(M = Co,Mo,V) were synthesized by high-speed mechanical ball-milling of the corresponding elemental metals and boron,and investigated as aqueous anode materials.The as-synthesized borides can achieve an excellent discharge capacity,about twice that of their parent transition metals.The metal boride electrodes also exhibit polarizations about 100-300 mV lower than those of their parent metals.The galvanostatic discharge curve of CoB0.5 shows a single discharge voltage plateau as a result of simultaneous electro-oxidation of elemental cobalt and/or amorphous cobalt boride.Both MoB0.5 and VB0.5 show two well-defined voltage plateaus,corresponding to the electro-oxidation of the corresponding metal and boride.These results show that the coexisting transition metal and boride in the metal borides co-activate each other in the ball-milling process,thereby significantly enhancing their electrochemical performances.
Rare earth metal oxides（REMO） as cathode electrocatalysts in direct borohydride fuel cell（DBFC） were investigated.The REMO electrocatalysts tested showed favorable activity to the oxygen electro-reduction reaction and strong tolerance to the attack of BH 4-in alkaline electrolytes.The simple membraneless DBFCs using REMO as cathode electrocatalyst and using hydrogen storage alloy as anodic electrocatalyst exhibited an open circuit of about 1 V and peak power of above 60 mW/cm 2.The DBFC using Sm 2 O 3 as cathode electrocatalyst showed a relatively better performance.The maximal power density of 76.2 mW/cm 2 was obtained at the cell voltage of 0.52 V.
