Electrochemical Behavior of Sodium Tungsten Bronze Electrodes in Acidic Media

Abstract

The electrochemical behavior of sodium tungsten bronze electrodes false(NaxWO3,normalwith x normalbetween 0.58 normaland 0.89false) has been examined in helium‐saturated 1N H2SO4 . Several techniques have been employed, e.g., steady‐state polarization, potentiodynamic scanning, galvanostatic charging, and open‐circuit decay of electrode potential. New data involving potential‐pH, rotating‐ disk, and thermogravimetric measurements on the sodium tungsten bronze electrode are also reported.The results indicate that the surface layer of a strongly anodized bronze electrode is depleted of sodium and its composition may approach WO3. On a strongly (cathodically) reduced NaxWO3 , formation of sodium‐hydrogen tungsten bronze false(NaxHzWO3false) is indicated. The reduction of a preoxidized (and hence sodium‐depleted) sodium tungsten bronze electrode produces hydrogen tungsten bronze HzWO3 .

Free Energy of Formation of Sodium Tungsten Bronzes, Na x WO 3

“…The sodium tungsten bronzes, Na~WO3, are highly nonstoichiometric compounds which are metallic conductors (1) and have therefore been used as electrodes for both fuel cells (2) and conductivity cells (3); yet until recently nothing quantitative was known about their thermodynamic properties. This paper reports some electrochemical studies of the sodium activity in these materials for 0.3 < x < 0.8 at ambient temperatures.…”

Hydrogen tungsten bronze as a decoking agent for long-life, natural gas-fueled solid oxide fuel cells

“…Tungsten bronzes M x WO 3 (M ¼ alkali metal and 0 < x < 1) have the perovskite structure in which the alkali-metal ion M + occupies the A-sites of the WO 3 perovskite framework formed by the corner-shared WO 6 octahedra. [40][41][42][43] As the content of M (the value of x) decreases, the lattice symmetry is lowered, for example, from cubic to tetragonal to orthorhombic. 40,[44][45][46] However, when M ¼ H as in the hydrogen tungsten bronze H x WO 3Àd , the tiny H + ions are positioned not at the A-sites of the ABO 3 perovskite structure but at the available sites among the 48 positions next to each oxide ion in the unit cell, forming hydroxyl groups with the oxide ions because the O-H-O bond distance is too long for hydrogen bonding if the H + ions are positioned at the A sites.…”

Inhibition Effects in the Electrochemical Reduction of Hydrogen Peroxide on Sodium Tungsten Bronzes

“…platinum were investigated. The cell and instruments employed, as well as the details of the electrode mounting, and gas purification were similar to those used in our recent work (4,5). Solutions were made from sulfuric acid (ULTREX, J. T. Baker Chemical), unstabilized hydrogen peroxide (Fisher Scientific Co., Certified), and conductivity water.…”