Tert-Butyl-alcohol-induced breakage of the rigid bubble layer that causes overpotential in the oxygen evolution reaction during alkaline water electrolysis

Abstract

Alkaline water electrolysis (AWE) requires low current densities (≤0.6–1.0 A cm–2) to proceed efficiently because a dense bubble layer covers the electrode surface at high current densities. Herein, we report on a simple method for promoting bubble detachment from an electrode surface and reducing the overpotential of the oxygen evolution reaction during AWE. This method involves the addition of tertiary alcohols that exhibit surfactant properties and are resistant to oxidation in the electrical field. Based on a dual-bubble layer model for reactant transfer, the increased ohmic resistance and diffusion resistance of the hydroxide ions induced by the bubbles attached to the electrode surface were alleviated by adding tert-butyl alcohol (TBA), while also retaining the charge transfer resistance. Consequently, the overpotential was reduced drastically at current densities of >2.0 A cm−2, and the tertiary alcohol effect was stable over several hours. The decomposition product of TBA was not detected after electrolysis at 3.0 A cm−2 for 10 h. We clarified that the addition of tertiary alcohols will improve the current density and productivity of the AWE system.