Gas flow Stimulated Hydrodynamics for Preparation and Application of Platinized Titanium Hollow Fibre Electrodes

In this study, Pt was electrodeposited on the surface of Ti hollow fibres from PtCl62- solution at fixed potential and at variable gas flow rate. Partial Pt coverage of Ti was obtained at flow rates <= 5 mL.min(-1), while a more-even geometrical distribution and linearly increasing Electrochemical Surface Area (ECSA) of Pt was obtained for flow rates of >5 and <20 mL.min(-1). Above 20 mL.min(-1), the morphology did not significantly change, and only a limited increase in ECSA of Pt (Pt-ECSA) was observed. Second, the performance of the Pt functionalized Ti-HFEs was evaluated at fixed potential in i) liquid phase oxidation of Fe-II to Fe-III, and ii) the hydrogen (gas) evolution reaction (HER). Generally, for the oxidation of Fe(CN)(6)(4-), a linear increase in current from 3 to approximate to 9 mA was found as a function of increasing gas flow rate. For the HER, a gas evolving reaction, initially (in the range of 0-10 mL.min(-1)) a much larger enhancement in current (from approximate to-10 to -35 mA) was observed than consecutively at higher flow rates. The effect of gas flow rate on Pt deposition, and utilization of platinized Ti HFEs, is explained on the basis of increasing fractional participation of relatively small pores at high flow rates, and generally an increasing mass transfer coefficient (k(M)) associated with localized mixing of the electrolyte near the electrode/electrolyte interface. The k(M) is roughly in the same order of magnitude as obtained in experiments using rotating disc electrodes.