Mixed phase titanium carbide (Ti-C-Tx): A strategy to design a significant electrocatalyst for oxygen electroreduction and storage application

A simple and cost-efficient approach is formulated to design a noble metal-free electrocatalyst for oxygen electroreduction. We report the preparation of mixed phase carbide through mechanical alloying method followed by annealing and hydrofluoric acid (HF) treatment. The structural analysis and morphological study confirm the formation of mixed phase titanium carbide (Ti-C-Tx). Interestingly, electrochemical studies exhibit significant oxygen reduction reaction (ORR) kinetics by Ti-C-Tx with improved onset potential of +0.87 V versus RHE and current density of 4.2 mA/cm2 in alkaline condition. Further, the obtained catalyst exhibits a single step first order ORR kinetics similar to commercial Pt/C catalyst. Additionally, Ti-C-Tx shows superior mass activity (∼100 mA/mg) compared with that of mechanically mixed sample [Ti-Al-C(BM); 14.47 mA/mg] and annealed sample [Ti-Al-C(1200); 20.25 mA/mg]. Interestingly, single step nearly four electron transfer pathway has been observed with less than 5% of peroxide formation with much better stability even after 10,000 cycles (with just 7 mV negative shift in E1/2) by Ti-C-Tx than that of Pt/C catalyst (with 40 mV negative shift in E1/2). Additionally, as-prepared Ti-C-Tx electrocatalyst demonstrates remarkable supercapacitive properties with a specific capacitance (Cs) of 126.4 F/g at 0.5 A/g in alkaline condition. Interestingly, though Ti-C-Tx comprises a mixed oxide composition, the major component TiC and the surface Ti-Ox species (thanks to non-stoichiometry of TiC0.67) are responsible for the enhanced ORR activity and remarkable supercapacitive behavior. Hence, it could be a promising candidate for energy conversion and energy storage device applications.