Abstract
RuO2 is commercially employed as an anodic catalyst in the chlor-alkali process. It is also one of the most active electrocatalysts for the oxidation of water, relevant to electrochemical water splitting. However, the use of RuO2 is limited by its low anodic stability under acidic conditions, especially at high overpotentials. In the present work, the electrochemical stability of model RuO2(110)/Ru(0001) anodes was investigated in order to gain a deeper understanding of the relation between structure and performance in Cl2 and O2 evolution reactions (CER and OER, respectively). Online electrochemical mass spectrometry was used to determine the onset potential of CER and OER in HCl and H2SO4 electrolytes, respectively. The onset potential of OER was higher in HCl than in H2SO4 due to competition with the kinetically more favorable CER. A detailed stability evaluation revealed pitting corrosion of the electrode surface with exposure of Ru(0001) metal substrate concomitant with the formation of a hydrous RuO2 in some areas regardless of the applied electrochemical treatment. However, despite local pitting, the RuO2(110) layer preserves its thickness in most areas. Degradation of the electrode was found to be less severe in 0.5 M HCl due to a decrease in the faradaic efficiency of RuO2 oxidation caused by competition with the kinetically more favorable CER.
Highlights
RuO2 is a common electrocatalyst which is primarily used for large-scale electrochemical production of Cl2 as a part of mixed oxide anodes (Dimensionally Stable Anodes, DSA®) [1e4]
The onset potential of OER is shifted to higher anodic potentials in HCl electrolyte due to the competing CER, while at the same time the critical potential remains independent of the primary electrochemical reaction, indicating that OER and RuO2 dissolution are not coupled
When electrodes were subjected to the critical potential, a significant dissolution of Ru was observed by elemental analysis of the electrolyte after testing
Summary
RuO2 is a common electrocatalyst which is primarily used for large-scale electrochemical production of Cl2 as a part of mixed oxide anodes (Dimensionally Stable Anodes, DSA®) [1e4]. To increase the stability of RuO2, it is commonly used in a mixture with other oxides such as TiO2, ZrO2, and Ta2O5 [3,14,15] This strategy, which results in improved corrosion resistance, was first applied in the fabrication of the so-called dimensionally stable anodes (DSA®), which show enhanced activity and structural stability during operation under corrosive electrochemical conditions [16]. It has been observed that the lower stability of electrochemically prepared amorphous (hydrous) RuO2 and the higher stability of thermally prepared crystalline RuO2 show an inverse relationship with OER activity [27] This is consistent with the observed correlation of the OER activity and the dissolution rate for a set of transition metals and their oxides [28]. We compare the stability of well-defined RuO2(110)/Ru(0001) single crystal model anodes under pure OER and competitive CER/OER conditions. Our multitechnique approach allowed us to follow the structural and compositional changes of the model electrode upon electrochemical treatment in different conditions, enabling a deeper understanding of the nature of the underlying physicochemical processes involved in anodic corrosion
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
