Porous 3D Inorganic Superstructure of Pd–Ir Aerogel as Advanced Support-Less Anode Electrocatalyst toward Ethanol Oxidation

For the first time, synthesis of Pd-Ir aerogel is reported in this manuscript. The Pd-Ir aerogel is synthesized using the controlled assembly of nanoparticles (NPs) (Ir and Pd) during the facile, surfactant-free, fast, and one-step gelation process in an aqueous environment followed by CO₂ supercritical drying. In this process, no chemical reagents are employed to induce the gelation, and change of temperature is employed to create anisotropic electrostatic repulsions between NPs. In addition, the kinetics and the type of product are controlled by the change of temperature. The Pd-Ir aerogel shows a three-dimensional (3D) architecture with a very high porosity and an ultralow density (0.016 g cm^-3). The Pd-Ir aerogel is applied as an advanced 3D electrocatalyst for the ethanol oxidation reaction (EOR) and offers a remarkable electrocatalytic efficiency (5416.1 mA mg_Pd ^-1) in a basic environment. The exceptional electrocatalytic activity and stability of the resultant aerogel are attributed to two crucial reasons: (1) unique structure of Pd-Ir aerogel and (2) synergistic effect of Ir element. Micro- and mesopore characteristics provide a large surface area, while macrospore characteristic guarantees accessibility to active sites. Furthermore, the self-supporting character of the Pd-Ir aerogel may hinder the degradation of durability observed in carbon-based electrocatalysts due to corrosion of carbonaceous support. Moreover, the Ir element as a co-metal in the structure of Pd-Ir aerogel acts as a very efficient promotor in the EOR and can change the electronic structure of Pd, which facilitates the electrooxidation of EtOH in alkaline media.