Synthesis of Iridium Nanocatalysts for Water Oxidation in Acid: Effect of the Surfactant

Abstract

Proton exchange membrane water electrolysers are very promising renewable energy conversion devices to produce hydrogen from sustainable feedstocks. These devices are mainly limited by the sluggish kinetics of the oxygen evolution reaction (OER). Therefore, efficient catalysts in acidic media that allow operating at low overpotential are necessary. Ir‐based nanoparticles are both active and stable for the OER. Surfactants are widely used in the preparation of nanoparticle colloids. A severe drawback for catalysis is the need to remove surfactants by typically costly, hazardous, time and/or energy consuming steps. Herein we present a modified approach of the polyol synthesis that consists of a simple surfactant‐free and NaOH‐free synthesis of Ir nanoparticles in ethylene glycol leading to colloidal nanoparticles of ca. 2.5 nm in diameter. The benefits and drawbacks of the surfactant‐free synthesis are illustrated by comparison with commercial Ir black nanoparticles and Ir nanoparticles obtained using surfactant for the electrocatalytic OER in acidic media.

Beyond Active Site Design: A Surfactant‐Free Toolbox Approach for Optimized Supported Nanoparticle Catalysts

“…With the development of new methods to test catalysts [58] and the demonstration of the toolbox approach with alternative precious metal catalyst like Ir [59] or Ru, [38] it is expected that this approach will be key to explore more complex materials like bimetallic catalysts, nanocomposites, [60] and more complex phenomenon like the joint effect of size and interparticle distance at the nanoscale, in order to develop more performant supported NP catalysts.…”

Surfactant-Free Colloidal Strategies for Highly Dispersed and Active Supported IrO2 Catalysts: Synthesis and Performance Evaluation for the Oxygen Evolution Reaction

“…The main advantage of the surfactant-free synthesis as compared to other colloidal methods is that the supported catalysts can be used as prepared since the Ir NPs are not covered by stabilizing polymers such as polyvinylpyrrolidone (PVP). 15,17 However, our results clearly show that the catalysts prepared by the polyol synthesis suffer from a material loss during the flocculation and redispersion steps required to remove the solvent. Despite the same particle size as in the Co4Cat approach, the ECSA is significantly reduced.…”

“…[12][13][14] In particular, synthesis procedures avoiding the use of surfactants recently gained momentum since they lead to active catalysts. 15,16 One standard in this respect is the polyol process, mainly using alkaline ethylene glycol (EG) as combined solvent, reducing and colloidal stabilizer agent. 17 In a recent advancement of the colloidal approach, low boiling point solvents could be used as a replacement for EG, in a process we refer to as Co4Cat, leading to readily active catalysts.…”

Surfactant-Free Colloidal Strategies for Highly Dispersed and Active Supported IrO2 Catalysts: Synthesis and Performance Evaluation for the Oxygen Evolution Reaction

“…20 This phenomenon would also explain the relatively small ECSA values determined in previous work. 15 The MeOH-based catalysts are instead characterized by a substantially higher ECSA, i.e. 195…”