Iridium Oxide Dendrite as a Highly Efficient Dual Electro-Catalyst for Water Splitting and Sensing of H₂O₂

Abstract

The synthesis and electrocatalytic performance of iridium-oxide (IrO 2 ) are reported. IrO 2 was electrochemically deposited on the gold dendrite template prepared by the chronoamperometry. The influence of the synthetic condition on the morphology, phase composition, and accessible surface area of the IrO 2 dendrites was investigated. The optimized IrO 2 dendrites showed an excellent electrocatalytic activity toward oxygen evolution with a low overpotential of 240 mV at 5 mAcm −2 and to the sensing of hydrogen peroxide with a high sensitivity of 692. The advantageous features of iridium oxide (IrO 2 ) include a high stability with exceptional resolution and corrosion resistances, reversible redox properties, and a sound biocompatibility for use in implantable devices. Due to these characteristic features, IrO 2 has been investigated for electrocatalytic applications such as water splitting, [1][2][3] pH sensing, 4,5 and amperometric biosensing; 6,7 however, its high cost and limited abundance require the most-efficient utilization of IrO 2 possible. 8,9 To enhance the electrocatalytic activity of IrO 2 at a low cost, IrO 2 catalyst is designed into a nanostructure. The structurally controlled IrO 2 catalyst can provide a large and accessible active surface area, and it facilitates electro-and mass transport. For these reasons, several researchers have developed the IrO 2 nanostructures in different ways. Electrodeposited IrO 2 nanoparticles for pH sensing were reported by Kim et al. 4 The preparation of IrO 2 nanofibers using electrospinning technique, and their application in ascorbic acid sensor electrode with binder was reported by Kim et al. 6 Sun et al. prepared IrO 2 nanorods using a CdSe/CdS/TiO 2 -nanorod template at 480• C. 10 With the use of a colloidal-SiO 2 template and heat-treatment, macroporous IrO 2 was prepared by Hu et al. 11 The reported IrO 2 structures were prepared via complex processes at high annealing temperatures or with the use of a template that required a multi-step preparation.As is well known, a dendrite structure, consisting of a main stem and numerous side branches, receives significant attention as a catalyst and other technological fields. The large surface area, short diffusion length, and sound mechanical integrity of the dendrite can provide both an extraordinarily high activated surface and a robust stability that are due to the micro-and nano-sized assemblies.12-15 To directly synthesize a metal dendrite on a conductive substrate, electrodeposition can be easily employed without any post-treatment at room temperature.Here, we introduce a simple method to achieve IrO 2 dendrite; the gold dendrite was prepared on titanium (Ti) foil using a facile electrodeposition (ED), and IrO 2 was then electrochemically deposited on the gold dendrite. There are only a few studies on the IrO 2 dendrite in the literature. The dendritic structure of IrO 2 was well controlled by the electrodeposition cycle number. An optimized IrO 2 electrode was applied to the electrocatalytic application f...

Key Strategies to Advance the Photoelectrochemical Water Splitting Performance of α‐Fe2O3 Photoanode

“…[41,50,[133][134][135][136][137] To improve the water oxidation kinetics of α-Fe 2 O 3 photoanodes, a variety of OECs have been loaded on their surface. The popular OECs for α-Fe 2 O 3 photoanode include cobalt phosphate (CoPi), [51,53,79,87,115,[138][139][140] IrO 2 , [83,[141][142][143] cobalt ions, [95,112] NiOOH, [78,144] nickel borate (NiBi), [77] and others. [145,146] The high abundance, low cost, low water oxidation overpotential, and self-healing property of CoPi make it an effective and extensively studied OEC.…”

“…[83,[141][142][143] The nanostructured IrO 2 needed a low overpotential (0.25 V) for water oxidation to achieve a photocurrent of 0.5 mAcm À 2 in comparison to CoPi (0.40 V). [143,160,161] Apart from these notable electrochemical properties, IrO 2 also possesses exceptional high stability, corrosion resistance, and most importantly reversible redox reaction characteristic. Thus, Tilley et al [83] reported the use of IrO 2 NPs to improve the performance of nanostructured cauliflower morphology α-Fe 2 O 3 photoanode.…”

Heterostructured Au–Ir Catalysts for Enhanced Oxygen Evolution Reaction

“…11,14 In this regard, advances in improving the OER activity of Ir have been achieved by alloying Ir with other metals, [17][18][19][20][21][22][23][24][25][26][27] as well as tailoring the geometric morphology of Ir catalysts. [28][29][30][31][32][33][34] The underlying mechanism is to: (i) optimize the intrinsic electronic structure of Ir sites to reach the summit of the activity volcano plot, which is characteristic of catalysts restricted by the scaling relation; and (ii) increase the number of exposed Ir sites in the catalysts.…”

“…To date, there have been a few reports on using AuIr bimetallic catalysts for enhanced OER. 20,21,[31][32][33][34] However, the activity improvement is generally attributed to the increased intrinsic activity of Ir sites because of the electron transfer either from Au to Ir 20 or from Ir to Au. 21,33 It remains unclear whether Au and Ir can be integrated as a phase-separated catalyst to perform OER tandem catalysis across the Au-Ir interfaces.…”

Novel NiFe/NiFe-LDH composites as competitive catalysts for clean energy purposes

“…On other hand, the WS requires the improvement of both efficiency and costs of production. For example, the utilization of noble metals as electrodes implies a good efficiency of the WS process [7,8] with low overpo-tentials for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) [9], but the cost of producing these electrodes is too high because the precursors are very expensive, and the large-scale applicability of these materials is difficult. As an alternative to reduce the costs for WS process, new procedures for easily fabrication and the development of new catalysts based on oxy/hydroxides of earth-abundant metals have been proposed since they have shown promising results for OER.…”