Synthesis of metallic nanoparticles for heterogeneous catalysis: Application to the Direct Borohydride Fuel Cell

International audience ; Until now, the fabrication of electrocatalysts to guarantee long life of fuel cells and low consump tion of noble me tals rema ins a ma jor ch allenge. The electrocatalysts based on me tals or me tal oxides wh ich are used today are limited by the complexity of the synthesis process and require several steps be fore depositing the catalysts on the substrate. We describe here a ch em ical synthesis process that consists of a single step of synthesizing and directly depositing catalysts such as gold (Au), palladium (Pd) and platinum (Pt) in the thickness of a carbon-fibe rs-based porous transport layer (PTL). The synthesis process essentially consists of dissolving in the same PGME A (Propylene glycol me thyl ether acetate) solvent a me tal precu rsor (HAu Cl 4 or Pd NO 2 or PtCl 4) and a homopolyme r PM MA (Polyme thylme tacrylate), then the me tal solution is deposited on the surface of the PTL after cleaning. The catalysts nanoparticles are created in real time on the surface of the fibe rs and in the volum e of the PTL un der specific annealing conditions. To validate the me thodology, some of the catalyst coated PTL ma terials have be en used as anode for the borohydride oxidation reaction (BOR) in a direct borohydride fuel cell (DBFC). It is shown that there is an optimu m loading of platinum (b elow 0.16 mg Pt / cm 2) wh ich constitutes the be st compromise be tween power density and faradic efficiency for the borohydride oxidation reaction (BOR). It is demonstrated that thanks to this low loading, hydrogen evolved du ring the anodic reaction is completely valorized. These electrodes have the advantages that the fabrication process is simple and fast, wh ile the performa nc e is improved with a very low platinum loading.