Water electrolysis on carbon electrodes enhanced by surfactant

In this paper, we present the water electrolysis on the carbon cloth electrode (CC) enhanced by a cationic surfactant, namely, hexadecyltrimethylammonium bromide (HTMAB). The influence of HTMAB on the two processes in water electrolysis, i.e., hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) was investigated. The results showed that an opposite effect of HTMAB on the HER and OER occurs with carbon-based electrodes, i.e., inhibiting the HER indicated as a small negative-potential shift, but enhancing OER as a large negative-potential shift. The improvement on the OER due to the introduction of HTMAB into H2SO4 is large enough to offset the declination of the HER in the water electrolysis. The enhancement of HTMAB on the OER is mainly due to accelerating H2O2 production from water oxidation at a relatively negative potential. The intermediate H2O2 in water electrolysis was detected and confirmed by an enzymatic method. The enhancement of HTMAB on the OER, however, was not observed on systems of Pt/H2SO4, CC/KOH and Ni/KOH. It shows that the mechanism of the water electrolysis on the different electrodes in the different electrolyte decides whether the HTMAB plays an enhanced role in the water electrolysis or not. All plausible reasons causing current increase in water electrolysis in H2SO4 apart from the catalytic effect of the HTMAB on enhancement of H2O2 production have been clearly eliminated. We conceive that there may be a possibility to obtain H2O2 rather than O2 besides H2 from the water electrolysis just using the carbon-based electrode with introduction of the cationic surfactant HTMAB as the electrolysis voltage is controlled within a certain range.