Three dimensional titanium molybdenum nitride nanowire assemblies as highly efficient and durable platinum support for methanol oxidation reaction

Boosting catalytic activity toward methanol oxidation reaction for platinum via heterostructure engineering

Direct methanol fuel cell (DMFC) is hampered by the sluggish methanol oxidation reaction. In this work, we have invited rhodium phosphides (Rh2P) to platinum (Pt) as robust MOR electrocatalyst ascribing the excellent water dissociation capability of Rh2P to generate Pt(OH)ads species to mitigate the CO poisoning. MOR mass activity of Rh2P-Pt/C is enhanced by 2- and 3.5-time with relative to commercial Pt/C and PtRu/C, respectively; additionally, the CO anti-poisoning ability is also boosted by 2.4 folds than Pt/C. The in-situ electrochemical impedance spectroscopy test reveals that the water dissociation is accelerated by Rh2P; moreover, the mutual electronic interplay between Pt and Rh2P contributes to a superior resistance towards electrochemical dissolution and coalescence. The theoretical investigation also indicates that d band center of Pt in Rh2P-Pt is downshifted resulting in a lower CO binding strength.

Structural and Electrochemical Properties of Nesting and Core/Shell Pt/TiO2 Spherical Particles Synthesized by Ultrasonic Spray Pyrolysis

Pt/TiO2 composites were synthesized by single-step ultrasonic spray pyrolysis (USP) at different temperatures. In an in-situ method, Pt and TiO2 particles were generated from tetra-n-butyl orthotitanate and chloroplatinic acid, and hydrothermally-prepared TiO2 colloidal dispersion served as Pt support in an ex-situ USP approach. USP-synthesized Pt/TiO2 composites were generated in the form of a solid mixture, morphologically organized in nesting huge hollow and small solid spheres, or TiO2 core/Pt shell regular spheroids by in-situ or ex-situ method, respectively. This paper exclusively reports on characteristic mechanisms of the formation of novel two-component solid composites, which are intrinsic from the USP approach and controlled precursor composition. The generation of the two morphological components within the in-situ approach, the hollow spheres and all-solid spheres, was indicated to be caused by characteristic sol-gel/solid phase transition of TiO2. Both the walls of the hollow spheres and the cores of all-solid ones consist of TiO2 matrix populated by 10 nm-sized Pt. On the other hand, spherical, uniformly-sized, Pt particles of a few nanometers in size created a shell uniformly deposited onto TiO2 spheres of ca. 150 nm size. Activities of the prepared samples in an oxygen reduction reaction and combined oxygen reduction and hydrogen evolution reactions were electrochemically tested. The ex-situ synthesized Pt/TiO2 was more active for oxygen reduction and combined oxygen reduction and hydrogen reactions in comparison to the in-situ Pt/TiO2 samples, due to better availability of Pt within a core/shell structure for the reactions.