Tunable electrochemical hydrogen evolution reaction employing surface acoustic waves

Abstract

Electrolysis of water is an attractive hydrogen generation method. As the most efficient catalyst for this reaction is platinum (Pt), what makes this approach expensive, many studies focus on enhancing the hydrogen producing efficiency of other inexpensive catalysts. In this study, an Au electrode and Au supported Pt/TiO₂ electrode without UV illumination were chosen as the catalyst for electrochemical hydrogen evolution reaction (HER) in acidic solution, and a Rayleigh-type surface acoustic wave (SAW) was used to promote the HER. Our results demonstrate that under the influence of SAW, both electrodes exhibit better HER activity with a higher current in the polarization curves from cyclic voltammetry. Analyzing the Tafel slope and the exchange current density with and without the effect of SAW suggests the enhancement of the HER activity especially at low overpotentials up to 100 mV. The effect strength increases with increasing power of the radio frequency (RF) signal. Various control experiments indicate that this is mainly induced by a microstreaming effect caused by the mechanical vibration of the SAW, while an off-resonance RF signal with a comparable electric field only reaches about 16.5 % of the increase of the current density at medium overpotentials. Thus, SAW-induced acoustic streaming is shown as tunable method to boost hydrogen production especially in the low and medium range of overpotential with promising potential for broader application in electrocatalysis and photocatalysis.