Thermally prepared Ti/RhOx electrodes: II H2 evolution in acid solution

Abstract

Ti/RhOx electrodes were prepared at 400-600°C by thermal decomposition of Rh chloride. Oxide layers were studied by SEM, cyclic voltammetry and steady-state E-j curves In 0.5 mol dm-3 H2SO4 solution. Voltammetric charge exhibits a maximum at 430°C with fresh electrodes which shifts to 470°C after use for H2 evolution. H2 discharge first produces a decrease in voltammetric charge, then an activation with final settlement to a constant behaviour for "aged" electrodes. H2 evolution on stable RhOx surfaces takes place with 40 mV Tafel slope and a reaction order of 2.5. The fractional reaction order indicates that the surface response to pH is that typical of oxides even for "aged" electrodes. A reaction mechanism is proposed

Effect of composition on the surface and electrocatalytic properties of Ti/IrO x +RhO x electrodes: H2 evolution from acidic solution

“…At the same time, a small reversible hump shows up around 0.4 V (SCE) as the content of RhO x becomes higher than 50 mol%. Such a small peak was observed also in previous works [13]. Figure 2b shows the effect of the calcination temperature on the CV curves of IrO x (70%) + RhO x (30%).…”

“…On the other hand, the 'true' electrocatalytic properties of pure RhO x are comparable to those of IrO x . In Figure 10b the 'true' electrocatalytic activity appears to increase with calcination temperature, an effect that has already been observed previously with RhO x -based electrodes [12,13].…”

“…This is also in agreement with previous work. Pure RhO x is reduced to metal under H 2 evolution and the CV curve evolves towards that of pure metal [13]. Thus, the incipient cathodic current is presumably related to the reduction of the surface oxide.…”

“…Recently, RhO x has been investigated in this laboratory [11][12][13][14]. RhO x exhibits better performances than RuO x and IrO x both in acids and in alkalis [3,4].…”

Thermally prepared Ti/RhOx electrodes IV: O2 evolution in acid solution

“…In a series of previous papers [9][10][11] we have studied the electrochemical properties of Ti/RhO x electrodes prepared by thermal decomposition of suitable precursors. In particular, RhO x has turned out to be more active than RuO 2 as well as IrO 2 for H 2 evolution in acid solution [10].…”