Promoting formic acid oxidation performance of Pd nanoparticles via Pt and Ru atom mediated surface engineering

The alteration of surface functional properties via incorporation of foreign atoms is supposed to be a key strategy for the enhanced catalytic performance of noble-metal based nanocatalysts (NCs). In the present study, carbon-supported palladium (Pd)-based NCs including Pd, PdPt and PdRuPt have been prepared via a polyol reduction method under the same reduction conditions as for formic acid oxidation reaction (FAOR) applications. By cross-referencing the results of the microscopic, spectroscopic and electrochemical analysis we demonstrated that adding a small amount of platinum (Pt) into Pd NCs (i.e. PdPt NCs) significantly promotes the FAOR performance as compared to that of Pd NCs via weakening the CO^ads bond strength at a lower voltage (0.875 V vs. NHE) than Pd (0.891 V vs. NHE). Of special relevance, the PdPt NC shows a mass activity (MA) of 1.0 A mg^-1 and 1.9 A mg^-1, respectively, in the anodic and cathodic scan. These values are ∼1.7-fold (0.6 A mg^-1) and ∼4.8-fold (0.4 A mg^-1) higher than those of Pd NC. Moreover, PdPt NC retains a higher MA (54 mA mg^-1) than that of Pd NC (9 mA mg^-1) after chronoamperometric (CA) stability tests over 2000 s. Meanwhile, further addition of ruthenium (Ru) (i.e. PdRuPt NCs) outstandingly enhances the CO tolerance during the CA test via removal of adsorbed CO^ads and thus shows the highest MA (62 mA mg^-1) after CA testing, which is higher than that of PdPt (54 mA mg^-1) and Pd (9 mA mg^-1) NCs. The intriguing results obtained in this study have great significance to provide further strategic opportunities for tuning the surface electronic properties of Pd-based NCs to design Pd-based NCs with improved electrochemical performance.