Electrocatalysis of Anodic Oxygen‐Transfer Reactions: Chloride‐Doped Lead Dioxide Electrodes

Abstract

The electrocatalytic activities were compared for pure and chloride‐doped normalbeta‐PbO2 films on gold and platinum substrates. Rate constants were increased significantly for oxidations of Mn2+, toluene, benzyl alcohol, dimethylsulfoxide and benzaldehyde in acidic media by the incorporation of Cl− into the oxide films. These reactions are concluded to occur by the electrocatalytic transfer of oxygen from H2O to the reaction products. Results of x‐ray diffraction studies indicate the Cl−‐doped PbO2 continues to have the slightly distorted rutile structure of pure normalbeta‐PbO2 . The observed electrocatalytic phenomena is concluded to be the beneficial consequence of surface defects generated when Cl− serves for charge compensation within the surface matrix and, thereby, increases surface sites capable of adsorbing hydroxyl radicals which are transferred in the electrocatalytic O‐transfer reactions.

Anodic oxygen-transfer electrocatalysis at iron-doped lead dioxide electrodes

“…4 and are summarized in Table I. It is readily confirmed that the 0-transfer activity of the [3] and speculated that the higher activity might be the result of a small quantity of Fe(II1) in the oxide as a result of dissolution of the substrate during deposition. The voltammetric response of CN-is shown in Fig.…”

Anodic oxygen-transfer electrocatalysis at iron-doped lead dioxide electrodes

“…A small mirror was placed under the electrolysis cell for observing the variation of color at the electrode. All other instrumentation has been described [3]. All potential values are given vs. the standard calomel electrode (SCE) reference.…”

“…Notable values are: 21 % at P-PbO, in 2 M HPF, (750 mA ern-,, 0 "C) [3], 35% at glassy 63 carbon (GC) in 7.3 M HBF, (600 mA cm-27 0 "C) [9], and 45% at GC in 62 wt % HBF, Pt (200 mA cm-2, -5 "C) [lo]. Here we compare the 03-evolution at Fe(II1)-doped and…”

“…The 0-transfer activity of electrodes consisting of electro-deposited p-Pb02 on noble substrates has been determined to be increased substantially when group (VA) metals [2,3] and some anions [4] are incorporated into the oxide film. The structure of the doped oxides has been determined to be virtually unchanged from that of the pure pPbO, (slightly distorted rutile), which is electrodeposited from acidic solutions of Pb (I1) in the absence of the doping ions.…”

“…-Anodic oxidation of dimethyl sulfoxide to dimethyl sulfone, i.e., (CH,),SO + H20 + -(CH,),SO, + 2H+ + 2e', has been used for intercomparison of electrode activities [3,6,13,18]. There are several reasons for this choice, including: i) (CH,),SO is unreactive at conventional anode materials (e.g., Au, Pt, GC); ii) the reaction mechanism is assumed to be relatively simple because only one oxygen is transferred; and iii) the reactant and product are uncharged and, therefore$ is presumed that double-layer effects can be ignored in the interpretation of catalytic phenomena.…”