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Since then the high activity of amorphous iridium oxide compared to crystalline IrO 2 is in the focus of research. This unique activity of HIROF was assigned to a high level of bulk defects and high surface concentration of active sites.
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18– 24 It was found out by Gottesfeld and Srinivasan 20 that the rate for oxygen evolution reaction on a hydrous iridium oxide film (HIROF) – often also called anodic iridium oxide film (AIROF) – is significantly increased compared to a bare iridium metal. 17 Iridium, among some other metals, is able to form an amorphous hydrous oxide under continuous potential cycling. An alternative way is the structural modification of iridium oxides, e.g. Nanoparticulated materials efficiently dispersed on a support, 5– 8 highly porous layers, 9– 11 core shell 12, 13 and mixed oxide systems 14– 16 have been suggested to reduce the loading of expensive elements. Since no inexpensive and suitable replacement for Ir has been found so far, current research efforts are directed toward a more efficient utilization of Ir based catalysts. 1– 3 Due to the high price and scarcity of Ir, however, widespread application of PEMWE using Ir-based catalyst is questionable. Crystalline IrO 2 is also considered as the anode catalyst, since it shows better stability and rather tolerable activity. 1 The obvious consequence of catalyst dissolution is the loss in active material and thus surface area, with potential secondary effects following. Additionally, high potentials and acidic environment on the anode side of a PEMWE lead to dissolution of the mentioned metals even though they are considered as noble. Due to slow kinetics of this reaction even on the state-of-the-art Ir and Ru based catalysts, the OER makes up a significant part of efficiency losses in an electrolyzer and therefore has the largest potential for improvement of the whole system. In both processes the oxygen evolution reaction (OER) will be the counter reaction on the anode side. producing hydrogen via proton exchange membrane water electrolysis (PEMWE) or converting carbon dioxide to valuable products in an electrochemical reduction process. Examples of promising technologies that could flank the renewables are e.g. Due to the alternating nature of power outcome from renewable energy sources, seasonal and/or local energy surplus has to be efficiently converted and stored to remain available at other times of high demand. In the future energy concept renewable wind and solar energy are considered to play an important role. These are discussed considering variations of oxide structure, morphology and electronic conductivity. Numerous peculiarities in the trend are however observed. The range of applied annealing temperatures is 100☌–600☌, with a general trend of decreasing activity and increasing stability the higher the temperature. (a) flat metallic iridium surfaces prepared by electron beam physical vapor deposition (EBPVD) and (b) electrochemically prepared porous hydrous iridium oxide films (HIROF) are studied. The OER activity and the dissolution of two different iridium electrodes, viz. In this work we investigate if the electrocatalytic performance of iridium can be fine-tuned by thermal treatment of catalysts at different temperatures. Limited abundance of iridium, however, poses limitations on widespread applications of these devices, in particular in the large scale conversion and storage of renewable energy. However, because the Earth’s core is rich in iridium, other scientists argue that iridium came from volcanic origin.Iridium is the main element in modern catalysts for the oxygen evolution reaction (OER) in proton exchange membrane water electrolyzers (PEMWE), which is predominantly due to its relatively good activity and tolerable stability in harsh PEMWE conditions. Many scientists believe that iridium originated from an asteroid or comet that was the cause of the extinction of the dinosaurs. This time period that marks the temporal border between the Cretaceous and Tertiary eras in geological time was identified by a thin layer of clay that contained an abnormally high level of iridium. The KT extinction event was a period over 65 billion years ago that marked the extinction of many forms of life such as, most popularly, the dinosaurs. Iridium salts vary widely in color, which is why iridium was named after the Latin word for rainbow: iris. Iridium is used as a hardening agent for platinum and for making tools that are exposed to high temperatures, like crucibles.