Fabrication of Iridium Based Electrocatalysts and Durable Supporting Materials for Proton Exchange Membrane Electrolysis

Abstract

Shining, shimmering and splendid may be a world with little atmospheric pollution. Using water as fuel can reduce concerns about environmental pollution. Water consists of one oxygen and two hydrogen atoms, which can be converted into individual gas molecules through an electrolysis process. This electrochemical conversion involves the hydrogen evolution reaction at the cathode and its counter reaction, the oxygen evolution reaction at the anode. These two reactions occur simultaneously and stoichiometrically; in the interim, the latter reaction is relatively slow and determines the overall rate of water splitting. Iridium-based materials can catalyze the oxygen evolution reaction without compromising both activity and stability. Conventionally, the electrocatalyst for the oxygen evolution reaction is placed onto or embedded into a carbonaceous substrate or support. However, carbonaceous materials are susceptible to corrosion during the oxygen evolution reaction, which leads to the loss of the electrocatalyst. In this regard, this dissertation covers strategies to circumvent the conventional corrosion problem caused by the use of carbonaceous materials as anodes for the oxygen evolution reaction. In the first strategy, the carbonaceous substrate is shielded by an iridium layer deposited thereon through an arc plasma deposition technique. The presence of the electrocatalytic shielding layer diverts the target of the electrochemical reactions from the substrate to the catalyst. In the second strategy, the carbonaceous catalyst support is strengthened through a heat-treatment process. Thereby, the physicochemical properties of the support material are altered and it becomes corrosion-resistant. In the last strategy, traditional carbonaceous substrates are substituted with titanium metals. The anodic electrodeposition of iridium oxide on the titanium substrate surface is enabled. At the end of this dissertation, the advantages and disadvantages of using each strategy are recapitulated and compared. The bottom line is that all the aforementioned strategies (shielding, strengthening, and substituting) should complement harmoniously each other to amplify the synergy, through which the production of hydrogen, an environmentally-benign fuel source, can be further facilitated.