Highly Reversible Water Oxidation at Ordered Nanoporous Iridium Electrodes Based on an Original Atomic Layer Deposition

Abstract

Nanoporous iridium electrodes are prepared and electrochemically investigated towards the water oxidation (oxygen evolution) reaction. The preparation is based on ‘anodic’ aluminum oxide templates, which provide straight, cylindrical nanopores. Their walls are coated using atomic layer deposition (ALD) with a newly developed reaction which results in a metallic iridium layer. The ALD film growth is quantified by spectroscopic ellipsometry and X‐ray reflectometry. The morphology and composition of the electrodes are characterized by scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, and X‐ray diffraction. Their catalytic activity is quantified for various pore geometries by cyclic voltammetry, steady‐state electrolysis, and electrochemical impedance spectroscopy. With an optimal pore length of L≈17–20 μm, we achieve current densities of J=0.28 mA cm−2 at pH 5 and J=2.4 mA cm−2 at pH 1. This platform is particularly competitive for achieving moderate current densities at very low overpotentials, that is, for a high degree of reversibility in energy storage.

Enhanced Oxygen Evolution Reaction Activity of Nanoporous SnO2/Fe2O3/IrO2 Thin Film Composite Electrodes with Ultralow Noble Metal Loading

“…The nanoporous Fe 2 O 3 , Fe 2 O 3 /IrO 2 , and SnO 2 /Fe 2 O 3 electrodes are characterized by nonlinear Tafel plots, with slopes increasing from 60 ± 10 mV per decade at low applied overpotential (η ≤ 0.48 V) to 170 ± 15 mV per decade at η ≥ 0.48 V. In comparison, the SnO 2 /Fe 2 O 3 /IrO 2 electrodes yield ≈150 and ≈580 mV per decade in these two regimes, respectively. Such large values of the Tafel slopes are characteristic of an OER that is no longer limited by the catalytic turnover at the surface, but by mass/charge transport in the pores . In practical terms, they express that our nanoporous electrodes are most efficient at lower applied overpotentials.…”

Efficient Electrochemical Hydrogenation of 5‐Hydroxymethylfurfural to 2,5‐Bis(hydroxymethyl)furan on Ag‐Displaced Nanotextured Cu Catalysts

“…The overall catalytic performance of these AgCu catalysts was comparable to that of the Ag nanoparticle (100 nm) catalyst. The influence of Ag displacement time (10,20,30, and 40 s) in 5 mM AgNO 3 on the catalytic performance of these AgCu catalysts was discernible, but not substantial. After 30 min of reduction at À 1.3 V vs. Ag/AgCl (À 0.56 V vs. RHE), these AgCu catalysts showed little difference in terms of BHMF yield, except for the 40 s-displaced AgCu catalyst that had a significant lower BHMF yield despite its high specific surface area.…”

“…The development of novel electrode materials with nanoscale structures has been recognized to be an important strategy to enhance the catalytic activities of electrodes. Some nanoscale‐structured metals, such as nanoporous metals, have distinct electrical and electrocatalytic properties, which endow them with promising applications in a wide variety of research fields, including catalysts, sensors, batteries, supercapacitors, and fuel cells . Among various techniques used to fabricate nanoporous metals, dealloying is the most used, owing to its simplicity and high efficiency .…”

“…Some nanoscale-structured metals, such as nanoporous metals, have distinct electrical and electrocatalytic properties, which endow them with promising applications in a wide variety of research fields, including catalysts, sensors, batteries, supercapacitors, and fuel cells. [24][25][26][27][28][29][30][31] Among various techniques used to fabricate nanoporous metals, dealloying is the most used, owing to its simplicity and high efficiency. [27,29] Dealloying refers to the selective dissolution of the active metal components from an alloy through chemical or electrochemical etching to produce a residual nanoporous structure.…”

Phosphate‐Based Electrocatalysts for Water Splitting: Recent Progress

“…It is noteworthy that iridium‐based materials show better intrinsic conductivity and electrolytic stability at high overpotential for OER, especially the IrO 2 . Thus, many researchers focus on designing Ir‐based catalysts . Sunde et al .…”