Enhanced Methanol Electro-Oxidation Activity of Pt/rGO Electrocatalyst Promoted by NbC/Mo2C Phases

Direct methanol fuel cells are attractive power conversion devices for portable and stationary applications. Many electrocatalysts have been explored for fuel cell applications but there is scope to design newer and more efficient electrocatalytic materials. For this purpose we have synthesized Mo2C and bimetallic NbC-Mo2C carbide phases by carbothermic reduction process. The carbide catalysts are characterized by various analytical techniques. The carbide samples are higly porous and their surface areas are of the order of 630 m(2) g(-1). Usually Pt is the state-of-the-art anode catalyst in direct methanol fuel cells. Here, Nb-Mo2C and 10 wt% Pt nanoparticles are deposited on reduced graphene oxide support to obtain Pt/Nb-Mo2C-rGO. This material shows highest mass activity of 836.4 mA mg(Pt)(-1) when compared to 10 wt% Pt/Mo2C-rGO and bare 20 wt% Pt/rGO catalysts. Notably, electrochemical tests show that the 10 wt% Pt/Nb-Mo2C-rGO catalyst exhibits lower onset potential, large electrochemical surface area, higher activity, and stability for methanol electro-oxidation in acidic solution compared to the Pt/Mo2C-rGO and Pt/rGO catalysts. The activty enhancement is atributed to the defective nature of the interface between Pt, Nb-Mo2C and rGO. It is found that Nb-Mo2C not only alleviates CO poisoning of Pt nanoparticles, but also generates oxygen containing species at lower potentials. This process helps scavenging the intermediate species such as COads on Pt surfaces and regenerates the active Pt sites for routine alcohol oxidation reaction. The chronopotentiometry and chronoamperometry studies also show that Pt/Nb-Mo2C-rGO exhibits lower alcohol oxidation overpotential and longer polarization time/stability compared to Pt/Mo2C-rGO and bare Pt/rGO catalysts.