An AFM Study of the Correlation of Lead Dioxide Electrocatalytic Activity with Observed Morphology

Abstract

PbO2 is widely employed as an electrocatalyst for anodic oxidation processes including the generation of oxygen and the degradation of various organic species in aqueous solution. However, despite extensive investigation, the precise mechanism of action remains obscure. In this paper we establish a previously unrecognized strong correlation between the morphology of the PbO2 deposits and their electrocatalytic activity. Cyclic voltammetric results are described for the electrodeposition of PbO2 on boron-doped diamond (BDD) electrodes from 2.5 mM solutions of lead(II) nitrate in nitric acid at pH values between approximately 0 and 7. A likely change in mechanism is observed around pH 4, consistent with the Pourbaix diagram of lead. The morphology of the PbO2 films is observed as a function of time and potential, using in situ AFM in each of the lead solutions. Information on the growth rates of the films is extracted, and the limitations of using AFM in such an application are discussed. It is shown that the deposit morphology depends strongly on the specific conditions used. The oxidation of a 100 mM glucose solution on electrodes modified by PbO2 deposition at a range of potentials and pH values is used as an indicator of the catalytic activity of the corresponding films, leading to the observation of the correlation between deposit morphology and catalytic activity mentioned above.

The influence of F− doping on the activity of PbO2 film electrodes in oxygen evolution reaction

“…At the PbO 2 /solution interface, PbO 2 has been shown to consist of a partially hydrated gel layer [16][17][18], generated by the following equilibrium process:…”

“…Since there is more Pb 6s character in the occupied states than in the empty states [8], here we define electron donors as Pb 3+ states. In the process of crystal formation, insoluble Pb 3+ species immobilized on the PbO 2 crystal surface have been observed [17]. The carrier concentration varies with preparation conditions in a way suggestive of defect-induced conductivity [20].…”

The influence of electrolyte media on the deposition/dissolution of lead dioxide on boron-doped diamond electrode – A surface morphologic study

“…Recently, studies of the deposition of PbO 2 onto BDD were performed under sonication [25] and microwave activation [26]. A direct correlation of lead dioxide electrocatalytic activity with morphology was also found [27].…”

Electroanalytical investigations on electrodeposited lead dioxide

“…More recently, Hyde et al [33] have studied the electrodeposition of PbO 2 on boron-doped diamond from lead nitrate in nitric acid solutions at various pH values. The deposit morphology depends strongly on the experimental conditions.…”