Well Controlled 3D Iridium Oxide/Platinum Nanocomposites with Greatly Enhanced Electrochemical Performances

It is crucial to improve charge storage capacity (CSC) and charge transport efficiency with low impedance for electrochemical capacitors. Here, a well‐controlled three‐dimensional (3D) nanocrystal platinum (Pt) is electrodeposited as the intermediate layer on microelectrode (200 µm in diameter) to provide extensive large surface area, followed by introducing iridium oxide (IrO x ) nanoparticles with excellent adhesion on the rough layer to fabricate high‐performance IrO x /Pt composite coatings. The uniform flower‐shaped coating presents a significantly low impedance ≈2.01 kΩ at 1 kHz (reduction of 94.52%). It has a cathodic CSC (CSC c ) up to ≈200.64 mC cm −2 , about 2, 17.51, and 56.18 times higher than that of nanocrystal Pt, IrO x , and flat Pt respectively. Robust chronic stability is observed with CSC c at ≈171.97 mC cm −2 after electrical stimulation for 12 d (>1 × 10 8 cycles). It also demonstrates record‐high charge injection capacity ≈6.37 mC cm −2 with excellent biocompatibility. Such coating is widely applicable for batch production on multichannel microelectrode arrays or substrates with different sizes. Moreover, it promotes excellent sensitivity to glucose detection up to ≈130 µA cm −2 m m −1 , with a linear range of 1–30 × 10 −3 m and a detection limit of 1.08 × 10 −6 m . The promising coating will pave a new way for various electrochemical applications.