Enhancement of the Performance of Pd Nanoclusters Confined within Ultrathin Silica Layers for Formic Acid Oxidation
The optimizing design of highly active and stable anode electrocatalysts is essential for high performance direct formic acid fuel cells (DFAFCs). Herein, a facile and cost-effective strategy was proposed to fabricate a robust ultrasmall Pd nanocluster confined within ultrathin protecting silica layers anchored on nitrogen doped reduced GO (NrGO) through generating amine functionlized graphene oxide with 3-aminopropyl triethoxysilane (APTES), followed tuning the thickness of protecting silica layers by precise control the amount of tetraethylorthosilicate (TEOS). The amine functionlized graphene oxide generated by APTES favors the formation of ultrasmall Pd nanoclusters due to the coordination of amine to PdCl24- while the confinement effect of ultrathin protecting silica layers stabilizes ultrasmall Pd nanoclusters and impedes agglomeration and sintering of ultrasmall Pd nanoclusters during a electrocatalysis. As a result, the ultrasmall Pd nanoclusters (~1.4 nm) confined in silica layers on NrGO (Pd/NrGO@SiO2) demonstrate very high forward peak current density for formic acid oxidation (FAO) of 2.37 A/mg, outperforming than that on the Pd/C catalyst (0.30 A/mg) and the Pd/rGO catalyst obtained by conventional method (0.42 A/mg). More importantly, our confined Pd catalysts indicate the highest stability of only 5% inconspicuous degradation of the initial mass activity after 1000 circles, compared with Pd/C (almost 100% loss), Pd/rGO (61.5% loss) and Pd/NrGO (73.2% loss). These strategies in this work provide new prospect in the design of excellent noble catalysts to overcome challenges for the practical application of DFAFCs.