•CoB/Ni-foam catalysts were prepared using electroless-plating method.•The catalysts showed excellent stability during the hydrolysis of NaBH4.•The catalysts were easily recovered by a magnet.•The controlled release of hydrogen were fulfilled conveniently.In this work, a series of shaped CoB/Ni-foam catalysts were directly synthesized by using a convenient and simple electroless plating method. Despite the low loading amount of CoB, the catalysts showed high catalytic performance in the hydrolysis of NaBH4 solution, and the maximum hydrogen generation rate reached 1930 mL min−1 (g CoB)−1 in 1 wt % NaBH4 + 5 wt % NaOH solution at 293 K. The catalysts demonstrated distinct stability, and the hydrogen generation rate was almost unchanged after 6 cycles. Furthermore, the catalysts could be easily recovered from the reaction system by a magnet. These characteristics make CoB/Ni-foam a high performance and cost effective catalyst for practical applications of hydrogen generation.Download high-res image (304KB)Download full-size image

As a promising energy source, direct borohydride fuel cells (DBFCs) have attracted a lot of attention. Since the electrooxidation of BH4− always accompanies the hydrolysis reaction, the energy density of DBFCs is closely related to the composition and structure of the anode. The formation of hydrogen formed by the hydrolysis of BH4− and the high exothermic nature of the reaction, as well as the strong basicity of the fuel, bring strict demands for the stability of the anode. Consequently, the designation and fabrication of an ideal anode are effective routes to enhance the performance of DBFCs. By comprehensive consideration of convenience, the electric/thermal conductivity of the electrode, the diffusion of the reactants/products and the effective cost, the electroless plating method was adopted and a CoB anode was directly formed on a Ni-foam substrate. The anode showed high electrocatalytic activities from electrooxidation of NaBH4 with a low CoB loading amount. Especially, the anode showed distinct stability compared to the CoB plate prepared by the pressed method and the catalytic activity could retain 65% after an accelerated life time test of 500 cyclic voltammetry cycles, which was due to the strong interactions between the CoB particles and Ni-foam substrate. Among all the investigated anodes, the CoB/Ni-foam electroless anode deposited for 7 times showed the best performance. It was applied in a membraneless DBFC which showed a maximum power density of 230 mW cm−2 in 1 mol L−1 NaBH4 + 3 mol L−1 NaOH at 313 K. These characteristics allowed the electroless plating CoB/Ni-foam catalyst to exhibit enormous potential as an anode for practical applications in DBFCs.

•W–CoB/Ag–TiO2 catalysts were prepared by electroless-plating method.•The catalysts showed high catalytic activity and stability on NaBH4 hydrolysis.•The catalysts were insensitive to air.•The reason for the high performance of W–CoB/Ag–TiO2 catalyst was explored.A one-step electroless plating method was applied to synthesize a series of TiO2 (activated by Ag) supported W modified CoB catalysts for H2 generation from hydrolysis of NaBH4. The modification amount of W was optimized and the highest H2 generation rate reached 7.27 L min−1 (g Co)−1 in 1 wt% NaBH4 solution (with 5 wt% NaOH as stabilizer) at 293 K, nearly 16% improvement over the undoped 3CoB/Ag–TiO2 catalyst. The catalytic activity was comparable with some noble metal catalysts. The catalyst could retain ∼50% of initial activity after 5 runs and was stable in ambient air. Further characterizations revealed that the high dispersion of W–CoB, the distinct mesoporous structure inherited from TiO2 support and the electron interactions among Co0, B0 and W0 might account for the high performance. The tungsten oxide existed on the surface of catalysts could act as Lewis acid to facilitate the adsorption of BH4−BH4− ions, which would further enhance the catalytic performance.

As a promising energy source, direct borohydride fuel cells (DBFCs) have attracted a lot of attention. Since the electrooxidation of BH4− always accompanies the hydrolysis reaction, the energy density of DBFCs is closely related to the composition and structure of the anode. The formation of hydrogen formed by the hydrolysis of BH4− and the high exothermic nature of the reaction, as well as the strong basicity of the fuel, bring strict demands for the stability of the anode. Consequently, the designation and fabrication of an ideal anode are effective routes to enhance the performance of DBFCs. By comprehensive consideration of convenience, the electric/thermal conductivity of the electrode, the diffusion of the reactants/products and the effective cost, the electroless plating method was adopted and a CoB anode was directly formed on a Ni-foam substrate. The anode showed high electrocatalytic activities from electrooxidation of NaBH4 with a low CoB loading amount. Especially, the anode showed distinct stability compared to the CoB plate prepared by the pressed method and the catalytic activity could retain 65% after an accelerated life time test of 500 cyclic voltammetry cycles, which was due to the strong interactions between the CoB particles and Ni-foam substrate. Among all the investigated anodes, the CoB/Ni-foam electroless anode deposited for 7 times showed the best performance. It was applied in a membraneless DBFC which showed a maximum power density of 230 mW cm−2 in 1 mol L−1 NaBH4 + 3 mol L−1 NaOH at 313 K. These characteristics allowed the electroless plating CoB/Ni-foam catalyst to exhibit enormous potential as an anode for practical applications in DBFCs.