Template synthesis of 3-DOM IrO2 powder catalysts: temperature-dependent pore structure and electrocatalytic performance

Abstract

Over the past decades, a tremendous effort has been put into developing cost-effective and highly active electrocatalysts toward oxygen evolution reaction (OER) for proton exchange membrane water electrolyzer. This report explores a hard-template-assisted pyrolysis method to fabricate IrO 2 electrocatalyst powders with hierarchically ordered porous structure. The effect of the calcination temperature on the pore structure and electrocatalytic property of periodically ordered macroporous IrO 2 material is studied. XRD, BET, and SEM characterizations show that the templated IrO 2 powders at 450°C exhibit the honeycomb array of macropores with cross-linking mesopores on the pore walls. The calcination temperature above 450°C will further lead to a growth of crystallite size and a loss of surface area. Once the calcination temperature exceeds 700°C that is higher than the glasstransition temperature of the SiO 2 template, the ordered porous structures of IrO 2 material are prohibited from the formation. The templated IrO 2 at 450°C shows substantially reduced electrocatalytic overpotentials for the OER, i.e., the efficiency increases as compared with other samples treated at higher calcination temperatures. As compared with the untemplated IrO 2 prepared by a simple pyrolysis method at 450°C, the 3-DOM IrO 2 (450°C) exhibited more than 2 times enhancement in BET area, voltammetric charges, and OER activity. It clearly reveals the control effect of the pore structure on the surface catalytic properties of iridium oxide. The present method is effective in improving the utilization of precious metals.

Applications of hierarchically structured porous materials from energy storage and conversion, catalysis, photocatalysis, adsorption, separation, and sensing to biomedicine

“…Kumar et al 71 have prepared a homogeneous, hierarchically porous nanotubular TiO 2 structure with uniform dimensions, which behaves as an efficient bifunctional electrocatalyst for oxygen and hydrogen evolution reactions in neutral medium. Hu et al 72 have fabricated IrO 2 electrocatalyst powders with 3D hierarchically ordered macroporous structure (3DOM) toward the oxygen evolution reaction (OER) in a proton exchange membrane water electrolyzer. Compared with IrO 2 prepared by a simple pyrolysis method at 450 1C, the 3DOM IrO 2 (450 1C) exhibits an over 2 times enhancement in the BET surface area, voltammetric charges, and OER activity.…”

Selective-leaching method to fabricate an Ir surface-enriched Ir-Ni oxide electrocatalyst for water oxidation

“…5. The pyrolyzed-IrO x sample yields an isotherm (type IV) with H1-type hysteresis that is typical of mesoporous materials with spherical aggregates, while the pyrolyzed-and leached-Ir 0.7 Ni 0.3 O x samples give type IV hysteresis of H3 which is usually produced by slit-like mesopores [44]. The corresponding BJH pore size distribution analysis based on the desorption branch (Fig.…”

“…(ESAs) of the corresponding samples[29,40,44].The q value of the leached-Ir 0.7 Ni 0.3 O x (14.0 mC cm −2 ) is approximately 3 and 2.5 times as that of pyrolyzed-Ir 0.7 Ni 0.3 O x (4.5 mC cm −2 ) and pyrolyzed-IrO x (5.5 mC cm −2 )…”

Ti-Doped SnO2 Supports IrO2 Electrocatalysts for the Oxygen Evolution Reaction (OER) in PEM Water Electrolysis

“…Nevertheless, catalyst stability issues caused by transition-metal dissolution are still unavoidable. Novel designed nanostructure noble metal oxides as an alternative research direction to enhance inherent activity have attracted much attention, such as the porous IrO x prepared by a template method , and core–shell nanostructure catalysts synthesized by a selective oxidation procedure. , The porous nanostructure of pristine IrO x enhances OER activity by fully utilizing the high specific surface area and mass transfer efficiency, while the improved performance of the core–shell structure can be attributed to (1) the increased specific surface area due to the synthesis method, (2) the introduction of transition-metal elements to tune the electronic structure of Ir, and (3) the introduction of nonprecious elements reduces the use of Ir species. In addition to improving intrinsic activity, a large number of studies have also been conducted from the perspective of increasing the number of active sites.…”