Reduction of Iridium Loading to the Minimum Level Required for Water Oxidation Electrocatalysis without Sacrificing the Electrochemical Stability

Abstract

Iridium(Ir)-based electrocatalyst exhibits an optimal trade-off between catalytic activity and stability and thus is considered one of the most promising candidates in acidic water oxidation electrocatalysis. Due to its cost and scarcity, however, the sparing use of it has become the top priority in this field. In this contribution, we demonstrate the immense potential of coaxial arc plasma deposition (APD) as catalyst coating technology for water oxidation. Taking advantage of controllable pulsed plasma generation with high kinetic energy, APD enables the rigid coating of uniform and ultrathin Ir films on the substrate surface. The strong anchoring propensity of the films is observed, and thereby, unless the Ir loading is too little to overcome the catalyst loss and dissolution caused during repetitive electrochemical redox cycling for full electrocatalyst activation, the electrocatalytic performance of the films remains unaffected even after thousands of cyclic water oxidation testing. In this regard, we scrutinize the threshold Ir loading required to elude the entire loss of catalyst and report the threshold value as a result of an analytic investigation into the correlation between the number of APD shots and the resulting mass of the iridium loading.