Abstract
The fundamental understanding of the electrode/electrolyte interface is of pivotal importance for the efficient electrochemical conversion and storage of electrical energy. However, the reasons for the low rate of electrocatalytic oxygen evolution and issues of long-term material stability, which are central constraints for attaining desirable efficiency for sustainable technologies like water electrolysis or electrochemical CO2 reduction, are still not completely resolved. While a lot of attention has been directed towards the search for new materials with unique (electro)catalytic properties, experimental results accumulated during the last four decades and prediction from models suggest that RuO2 possesses superior activity for oxygen evolution under acidic conditions. Considering that RuO2 is a material of choice, we show that tailoring the surface morphology on the meso- and macroscale has great potential for the improvement of the efficiency of this gas evolving reaction. Advanced analytical tools have been utilized for the combined investigation of both activity and stability. Namely, the potential dependent frequencies of gas-bubble evolution, an indicator for the activity of the electrode, were acquired by scanning electrochemical microscopy (SECM), while the dissolution of RuO2 was monitored using a micro electrochemical scanning flow cell combined with an inductively coupled plasma mass spectrometer (SFC-ICP-MS). The obtained fundamental insights will aid improving the design and thus performance of electrode materials for water oxidation.
Highlights
The production of chemicals for energy storage has received a lot of attention as an integral part of a renewable energy concept.[1,2,3,4,5,6] Thechemical energy conversion conceptually relies on postulates ofcatalysis, which are typically based on the impact of the nature of the electrode material on the rate of the reaction.[7]
In this study we investigate the impact of the surface morphology on the oxygen evolution reaction (OER) activity and the catalyst stability of RuO2 samples
The volume change of the gel-body during the drying and thermal treatment steps is restricted by the substrate, which results in an internal stress that depends on the density change of the coating during drying and the mismatch in the coefficients of thermal expansion between thin coating and thick substrate
Summary
The production of chemicals for energy storage (hydrogen, methanol, methane.) has received a lot of attention as an integral part of a renewable energy concept.[1,2,3,4,5,6] The (electro)chemical energy conversion conceptually relies on postulates of (electro)catalysis, which are typically based on the impact of the nature of the electrode material on the rate of the reaction.[7]. The high overpotential for the OER originates in the necessity to exchange four electrons during the (electro)catalytic process and the formation of at least three adsorbed intermediates.[10] The preferences of different materials for the adsorption/desorption of these oxygen containing intermediates are believed to be the determining factors for the reaction rate. Several catalytic descriptors (for example, binding energies of key intermediates, O*, OH*, and OOH*) have been used to theoretically predict and explain the extensively studied activity trends, which are usually represented in the form of so-called “volcano” plots.[11,12,13,14] The general perception is that RuO2 is positioned at or close to the top of the “volcano”, since it does not bind the reaction intermediates too strongly nor too weakly, so that according to the Sabatier principle the kinetics for generation of molecular oxygen during the water oxidation is at a maximum.[12]
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