The electrochemical oxidation of organics using tungsten oxide based electrodes

Abstract

High surface area tungsten oxide (WO x ) based electrodes containing centers of Pt, Sn or Ru were synthesized. The WO x electrodes were found to display good capacitive behavior and relatively high specific capacitance values of up to 180 F gThe oxidation behavior of particularly HCOOH and (COOH) 2 , using the WO x electrodes containing Pt and Sn centers (Pt/WO x and Sn/ WO x , respectively), was studied in detail in aqueous solutions at high potentials, i.e. at which O 2 is evolved. Both HCOOH and (COOH) 2 appear to be oxidized following 1st order kinetics. The (COOH) 2 oxidation reaction is faster than the HCOOH reaction using otherwise the same experimental conditions. The reaction mechanism of both the HCOOH and (COOH) 2 oxidation was found to most likely involve the adsorptive interaction of the two organics with the anode surface. The WO x based anodes appear to be promising catalysts for the anodic oxidation of both (COOH) 2 and HCOOH. #

Anodic oxidation of oxalic acid using WOx based anodes

“…It is seen ( Fig. 1 [6]. Therefore, all WO x electrodes studied in this work were conditioned in 2 M H 2 SO 4 at 10 (2 Ac m (2 for 7 days before they were used as anodes for the (COOH) 2 oxidation studies.…”

“…Tungsten oxides (WO x ) containing Pt 'micro'-centers (and referred to as Pt/WO x in this work) were formed electrochemically at (/0.645 V versus a saturated calomel electrode (SCE) using a method described elsewhere [6,7]. The oxide films were deposited from a 0.1 M tungsten solution (see below) also containing 8 mM H 2 PtCl 6 (Alfa Aesar, 99.9% metals basis).…”

“…Immediately prior to the formation of the IrO 2 layer, the Ti substrates were mechanically polished using sandpaper, ultrasonically cleaned in EtOH, etched in boiling (80 8C) 10 M HCl for 10 min, and then well rinsed with H 2 O. It is known that tungsten oxide films can be deposited onto a variety of conductive substrates [6,7]. In this work, the oxide films were deposited onto the IrO 2 coated Ti substrates, as it is well known that the lifetime of oxide anodes can be enhanced in this manner [8].…”

“…The PtO is reduced to metallic Pt in the cathodic scan. Cycling up to 1.09 V in 0.5 M H 2 SO 4 results in the formation of one monolayer of PtO [6,9]. Therefore, the PtO to Pt reduction peak can be used to obtain an estimate of the electro-active Pt area within the WO x film using a conversion of 420 mC per cm 2 Pt [9].…”

“…In previous work [6] the potential use of tungsten oxide (WO x ) based anode catalysts, as a novel anode material for the anodic oxidation of organics, has been discussed. It has been shown that these WO x based anode catalysts that also contain 'micro'-centers of a foreign metal such as Pt or Sn show promising catalytic properties for the anodic oxidation of HCOOH and (COOH) 2 .…”