Efficient OER Catalyst with Low Ir Volume Density Obtained by Homogeneous Deposition of Iridium Oxide Nanoparticles on Macroporous Antimony‐Doped Tin Oxide Support

Abstract

A multistep synthesis procedure for the homogeneous coating of a complex porous conductive oxide with small Ir nanoparticles is introduced to obtain a highly active electrocatalyst for water oxidation. At first, inverse opal macroporous Sb doped SnO 2 (ATO) microparticles with defined pore size, composition, and open-porous morphology are synthesized that reach a conductivity of ≈3.6 S cm −1 and are further used as catalyst support. ATO-supported iridium catalysts with a controlled amount of active material are prepared by solvothermal reduction of an IrO x colloid in the presence of the porous ATO particles, whereby homogeneous coating of the complete outer and inner surface of the particles with nanodispersed metallic Ir is achieved. Thermal oxidation leads to the formation of ATO-supported IrO 2 nanoparticles with a void volume fraction of ≈89% calculated for catalyst thin films based on scanning transmission electron microscope tomography data and microparticle size distribution. A remarkably low Ir bulk density of ≈0.08 g cm −3 for this supported oxide catalyst architecture with 25 wt% Ir is determined. This highly efficient oxygen evolution reaction catalyst reaches a current density of 63 A g Ir −1 at an overpotential of 300 mV versus reversible hydrogen electrode, significantly exceeding a commercial TiO 2 -supported IrO 2 reference catalyst under the same measurement conditions.

Two‐Dimensional Metal‐Organic Framework Nanosheet Supported Noble Metal Nanocrystals for High‐Efficiency Water Oxidation

“…[4] Many efforts have been made to develop effective strategies to the reduce noble metal loadings. [5][6][7] Commercial noble metal based electrocatalysts, such as Ir/C and Pt/C catalysts, are generally prepared by a direct solvothermal method or impregnation with metal precursors followed by thermal reduction. [8][9][10] However, the initially well-dispersed noble metal nanocrystals (NMNCs) in these commercial electrocatalysts tend to agglomerate into large particles after some working time due to the weak interaction between the NMNCs and carbon support, [11] thus causing a deterioration of the activity.…”

Iridium-Doped Nanosized Zn–Al Layered Double Hydroxides as Efficient Water Oxidation Catalysts

“… 3 − 6 For this reason, many research groups are focusing on the optimization of WOCs in a “noble-metal atom economy” fashion, that is, trying to maximize the exploitation of the Ir/Ru centers while minimizing their content in the catalytic systems. 5 , 6 “Noble-metal atom economy” can be pursued in the development of all three types of catalysts, namely molecular, 7 − 13 heterogenized, 5 , 14 − 19 and heterogenous 6 , 20 − 24 systems.…”

Molecular and Heterogenized Cp*Ir Water Oxidation Catalysts Bearing Glyphosate and Glyphosine as Ancillary and Anchoring Ligands

“…[9][10][11][12][13][14] In general, catalysts based on noble metals, like iridium and ruthenium, [8,[15][16][17] exhibit better performances than the earthabundant homologues. [18][19][20] To overcome the drawbacks related to their limited availability, three main strategies have been explored consisting in classically utilizing very active molecular catalysts (at very low concentration), [21][22][23][24][25][26][27][28][29] or in maximizing the number of accessible active sites in properly designed heterogenized [8,[30][31][32][33][34][35] and heterogeneous [17,[36][37][38][39][40][41] catalysts, according to the 'noble metal atom economy' principle. [8] The preparation of supported catalysts can be particularly convenient in this respect.…”