The Effect of Carbon Content on Methanol Oxidation and Photo-Oxidation at Pt-TiO2-C Electrodes

Abstract

The oxidation of methanol is studied at TiO2-supported Pt electrodes of varied high surface area carbon content (in the 30-5% w/w range) and C÷Ti atom ratio (in the 3.0-0.4 ratio). The Pt-TiO2 catalyst is prepared by a photo-deposition process and C nanoparticles (Vulcan XC72R) are added by simple ultrasonic mixing. The optimum C÷Ti atom ratio of the prepared catalyst for methanol electro-oxidation is found to be 1.5, resulting from the interplay of C properties (increased electronic conductivity and methanol adsorption), those of TiO2 (synergistic effect on Pt and photo-activity), as well as the catalyst film thickness. The intrinsic catalytic activity of the best Pt-TiO2/C catalyst is better than that of a commercial Pt/C catalyst and could be further improved by nearly 25% upon UV illumination, whose periodic application can also limit current deterioration.

Nanoscale Chevrel-Phase Mo6S8 Prepared by a Molecular Precursor Approach for Highly Efficient Electrocatalysis of the Hydrogen Evolution Reaction in Acidic Media

“…Pristine CP Mo 6 S 8 is known to be a semiconducting material with a deficiency of electrons near the Fermi level. , Hence in a first attempt to increase the conductivity of the catalyst we incorporated commercially available conductive carbon into the material at various ratios (0–40% w/w) by simply mixing the pristine material with the latter in the solid state (see the Experimental Section). This modification approach is adopted in the literature for improving the electronic conductivity of several semiconducting electrocatalysts, such as TiO 2 − and MoS 2 , and it has been also used recently for CP Mo 6 S 8 HER catalysts . From the results displayed in Figure a,b, it can be seen that adding 20% w/w of conductive carbon into the catalyst mixture shifts the onset potential to more positive values by ca.…”

Ultrafast Growth of a Cu(OH)2–CuO Nanoneedle Array on Cu Foil for Methanol Oxidation Electrocatalysis

“…Methanol oxidation electrocatalysis is one of the widely studied energy conversion reactions that has direct application in direct methanol fuel cells (DMFCs), proton exchange membrane fuel cells (PEMFCs), and in oxygen evolution reaction (OER) masking for energy-efficient hydrogen production from water electrolysis. − Methanol oxidation electrocatalysis has conventionally been carried out by Pt and its alloys with other metals such Ru and Co in either acid or in alkali as they show the lowest onset overpotential when compared to other materials. − However, the surfaces of Pt and its alloys suffer from catalytic poisoning upon prolonged use . There are contradicting claims regarding the poisoning of Pt surfaces in methanol electrocatalytic oxidation in which a majority of researchers have accepted that the Pt surface coordinates to carbon monoxide (CO) formed in situ upon the partial oxidation (four electron and four proton-coupled reaction) very strongly through π-backbonding between Pt-centered d-orbitals and C-centered sp-orbital of CO. − ,− However, there are a few studies which claim that the activity diminishing was actually due to the surface oxidation of Pt to Pt-O x and not by the coordination of CO on the surface of Pt. ,, These issues generally do not occur when methanol oxidation electrocatalysis is carried out with nonprecious metals and their compounds such as Ni, ,,− Co, ,− W, and Cu ,,− as they always oxidize methanol completely taking up a water molecule from the electrolyte solution (six electron and six proton-coupled reaction with a C–O bond formation).…”

Half-Sphere Shell Supported Pt Catalyst for Electrochemical Methanol Oxidation

“…analysis. The increased methanol oxidation activity is mainly attributed to the consequence of the existing surface bridging hydroxyls which are bonded spontaneously onto the HSS surface once it is exposed to any forms of water (42,43,61) . In addition, the improved activity is also benefited from the Nb-TiO2-HSS nanostructures and the water bonding property of Nb-TiO2, which have been previously explained by Pan et al (23) .…”