Metal oxide supported iridium electrocatalysts for the oxygen evolution reaction

Abstract

Currently the production of hydrogen is done through oil derivatives which pollute a lot and have reserves that are beginning to be scarce for the next few years. For these reasons, there is the need to produce green hydrogen. Obtaining this hydrogen is currently becoming a necessity to be able to store renewable energy and use it when needed, contributing against the climate change by reducing carbon dioxide. To produce hydrogen from the electrolysis of water, the anode is the bottleneck. Therefore, new catalysts must be obtained that are able to better catalyze this reaction while reducing energy and economic costs. The main objective of this work is to obtain new catalysts for the oxygen evolution reaction, with the aim to minimize the amount of precious metals. The electrocatalysts, iridium nanoparticles and mixture of iridium with ruthenium, were supported on TiO2 anatase nanopowders to increase their active area and to obtain a better electrochemical performance in acidic conditions using 0.1 M HClO4. The method used to reduce the iridium nanoparticles on the substrate was the polyol assisted reduction technique in a microwave at 140 ºC for 20 min. The electrocatalysts were characterized and compared with the commercial Ir-Black catalyst. Ir-anatase samples have been studied in the range of 5 to 40 wt.% Ir, requiring at least 10 wt.% of the metal. It was also possible to obtain two samples with a mixture of iridium and ruthenium with 20 and 40 wt.% of active catalyst phase. Two functional catalyst have been also obtained, one with 10 wt.% iridium on anatase nanoparticles and the other with a theoretical 40 wt.% of a mixture of iridium and ruthenium with different electrochemical properties. The microwave technique is good for the deposition of iridium nanoparticles but it is not too suitable to deposit ruthenium, since it does not sufficiently adhere to anatase, proving that the use of the support is a key part for the good performance of the catalyst