A binder‐free Ir0.4Ru0.6‐oxide/functionalized multi‐walled carbon nanotube electrode for possible applications in supercapacitors

An initial study on a simple and inexpensive method to form an Ir_0.4Ru_0.6‐oxide (MMO) coating onto high‐area plasma functionalized multi‐walled carbon nanotubes (f‐MWCNTs) at the bench‐scale for possible supercapacitor (SC) applications is presented. f‐MWCNT electrodes are prepared in a two‐step process combining the growth of MWCNTs directly onto a 316 stainless steel mesh by thermal‐chemical vapour deposition (t‐CVD), followed by the addition of oxygen‐containing functionalities to their surface by plasma functionalization. The plasma functionalization step is done to: (i) improve electrode wettability and (ii) improve capacitive properties through the addition of pseudocapacitive oxygen functionalities. A simple dip‐dry method is then employed to coat the f‐MWCNTs with the desired MMO coating (Ir_0.4Ru_0.6‐oxide) prepared initially in a liquid precursor mixture. f‐MWCNT electrodes are suspended and dipped into the precursor then heated in air to evaporate the solvent while building the oxide layer. The resulting MMO/f‐MWCNT electrode exhibits excellent stability in 4 mol/L KOH electrolyte, yielding larger specific capacitance values than those obtained on bare f‐MWCNT electrodes; at a charging/discharging current density of 0.5 mA cm^?2, the MMO/f‐MWCNT and f‐MWCNT electrodes achieve specific capacitances of 664 ± 7 and 190 ± 30 F g^?1 in a 3‐electrode cell, respectively. The MMO/f‐MWCNT electrodes show good rate capability performance up to 10 mA · cm^?2 and excellent stability.