Herein, the effect of the alkali cation (Li + ,Na + ,K + , and Cs + )inalkaline electrolytes with and without Fe impurities is investigated for enhancing the activity of nickel oxyhydroxide (NiOOH) for the oxygen evolution reaction (OER). Cyclic voltammograms showthat Fe impurities have asignificant catalytic effect on OER activity;h owever,b oth under purified and unpurified conditions,the trend in OER activity is Cs + > Na + > K + > Li + ,suggesting an intrinsic cation effect of the OER activity on Fe-free Ni oxyhydroxide.I nsitu surface enhanced Raman spectroscopy( SERS), shows this cation dependence is related to the formation of superoxo OER intermediate (NiOO À ). The electrochemically active surface area, evaluated by electrochemical impedance spectroscopy (EIS), is not influenced significantly by the cation. We postulate that the cations interact with the NiÀOO À species leading to the formation of NiOO À ÀM + species that is stabilized better by bigger cations (Cs + ). This species would then act as the precursor to O 2 evolution, explaining the higher activity.Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.

The electrochemical chlorine evolution reaction (CER) and oxygen evolution reaction (OER) represent core processes in the production of chlorine, relevant to bulk chemical manufacturing, and water splitting, the most promising technology for renewable energy storage. Unfortunately, because of an apparent coupling between their key binding intermediates, the two reactions can easily occur simultaneously, which is never an attractive outcome. In this work, using a series of iridium-based double perovskites and rotating ringdisk voltammetry to deconvolute parallel OER and CER currents, we explored the interdependence of CER and OER in dilute acidic chloride solutions of up to 120 mM, where both reactions may occur in parallel with similar current densities. We also employed online inductively coupled plasma-mass spectrometry (ICP-MS) measurements to probe the material stability and its dependence on chloride concentration. For all studied materials, we found a strong linear correlation between CER and OER activity as well as a comparable selectivity, strengthening the suggestion that OER and CER follow a scaling relationship. It was also found that chloride selectively enhances the dissolution of the noble metal component. A reaction order analysis was performed to gain insight into the CER mechanism, the effect of surface area changes due to adventitious leaching, and the observed suppressing effect of chloride on OER.

The electrocatalytic oxidation of small organic molecules is of general importance for energy-related issues such as the fuel cells and electrochemical re-formation. The common emergence of current/potential oscillations in these reactions has implications on mechanistic aspects as well as on the overall conversion, and thus on the performance of practical devices. We investigate in this paper some general features of the electro-oxidation of formaldehyde, formic acid, methanol, and ethanol on platinum and in acidic media, with emphasis on the comparison of the activity under conventional and oscillatory regimes. The comparison is carried out by different means and generalized by the use of identical experimental conditions in all cases. In all four systems studied, the occurrence of potential oscillations is associated with excursions of the electrode potentials to lower values, which noticeably decreases the overpotential of the anodic reaction, when compared to that in the absence of oscillations. Quantitatively speaking, a 2-fold enhancement in the power density was observed in an idealized fuel cell operated with formaldehyde. This aspect, together with spontaneous self-cleaning processes, presents important advantages to the use of autonomous oscillations to reach both higher and long-term activities. Finally, some mechanistic aspects of the studied reactions are also discussed