The influence of electrochemical pre-treatment of B-doped diamond films on the electrodeposition of Pt

Abstract

Este trabalho trata da influência do pré-tratamento eletroquímico de eletrodos de diamante dopado com boro (DDB) em meio ácido, na eletrodeposição de platina. Pt não pôde ser eletrodepositada em eletrodos de DDB recém-preparados. Entretanto, pré-tratamentos baseados em varreduras de potenciais ou em polarizações anódicas a potencial constante em curtos intervalos de tempo ativaram o eletrodo para a deposição de Pt. O tratamento anódico desempenha diferentes papéis, de acordo com o tempo de tratamento: em tempos curtos, a deposição de Pt é aumentada, ao passo que tempos de polarização mais longos inibem o processo de eletrodeposição de Pt, originando, entretanto, depósitos com maior área superficial. Tais resultados são discutidos em termos de mudanças na hidrofilicidade da superfície do DDB, bem como na apassivação da superfície, provavelmente representada pela oxidação da mesma.The influence of the substrate electrochemical pre-treatment in 0.5 mol L -1 H 2 SO 4 on the Pt electrodeposition on boron-doped diamond, BDD, film electrodes was investigated. Platinum cannot be electrodeposited on a freshly prepared BDD electrode; however, potentiodynamic cycling or anodic potential steps at short times does activate the electrode. Anodic pre-treatment plays a dual role in the behavior of Pt deposition on BDD surfaces: Pt deposition is increased at short-term anodic pre-treatments, whereas at longer pre-treatment times Pt deposition was inhibited. These facts are explained in terms of wettability changes and passivation of the surface. Conversely, the oxide layer formed in these treatments increases the dispersion level of the catalyst.Keywords: boron-doped diamond electrodes, Pt electrodeposition, electro oxidation IntroductionAs Solar Energy technology is not yet fully developed to be commercially employed, fuel cells constitute one of the best alternative for energy conversion devices as a substituent to the pollutant fossil fuel powered engines. 1 Several electrode materials have been proposed for fuel cells. In these devices, the electrode is basically constituted of Pt clusters anchored on finely divided carbon black substrate. For this reason, the dispersion of electrocatalysts on carbonous materials has been intensely investigated. Among several parameters, the nature and pre-treatment of the substrate arise as interesting ways to control important characteristics like the size, stability and activity of the electrocatalyst particles. Several authors have studied the influence of the nature of the substrate on the electrocatalytic activity of platinum dispersions and it was observed for example, that the work function of the substrate can strongly influence the activity of the electrocatalyst.2 It was shown that the electrocatalytic activity of Ag dispersions for O 2 cathodic reduction increased as the carbonous substrate oxidation level increased.3 Thus, oxidative pretreatment of the carbonous substrate can influence the dispersion and activity of the catalyst. Conversely, different authors have noted that dis...

Platinum Electrodeposition on Conductive Diamond Powder and Its Application to Methanol Oxidation in Acidic Media

“…41 Other groups have also used electrodeposition. 42,45,46 In the present work, the deposition of platinum was performed by continuously cycling the potential of the coated electrodes ͑scan rate 20 mV s −1 ͒ within the potential range 0.5 to −0.2 V in a nitrogen-saturated 0.5 M H 2 SO 4 solution. Cyclic voltammograms were recorded, and the deposition process was continued until a stable voltammetric response was obtained ͑typically, after ca.…”

“…[37][38][39] A number of recent studies have shown promising electrochemical results for Pt and Pt-based alloy particles on nonporous BDD films, particularly for methanol oxidation. [40][41][42][43][44][45][46][47][48][49][50][51][52][53] Little work has been reported thus far for conductive diamond powders, which are not readily available; however, BDD powders with particle sizes in the 1-50 m range have been prepared by depositing a boron-doped layer on nondoped diamond powder 54 and by milling freestanding BDD films. 55 In the future, it is expected that commercially available nondoped diamond nanoparticles will be able to be doped with boron.…”

Reusable Platinum Nanoparticle Modified Boron Doped Diamond Microelectrodes for Oxidative Determination of Arsenite

“…With differences in grain sizes, grain boundaries, and levels of doped boron, the number of multistep cycles was examined for these two BDD electrodes in order to attain the maximum response for As(III). However, activation by potentiostatic anodic polarization in 0.1 M H 2 SO 4 at 2.0 V versus Ag/AgCl for 10 min was mandatory. This anodic treatment reduces the BDD background current by eliminating adsorbed hydrogen and the sp 2 graphitic phase.…”

Relative deactivation of boron-doped diamond (BDD) and glassy carbon (GC) electrodes in different electrolyte media containing substituted phenols – Voltammetric and surface morphologic studies

“…Moreover, repeated electrochemical cleaning of the BDD surface decreases the electrode activation. This attributes to the electrostatic inhibition exerted by the oxygen present on the surface and these groups can form an oxide layer which can produce an electrostatic inherence effect [34].…”