Binder- free iridium based electrocatalysts: Facile preparation, high activity and outstanding stability for hydrogen evolution reaction in acidic medium.

Herein, we develop various iridium based catalysts using titania, zirconia and ceria as a supporting material (Ir/MO; M = Ce, Ti, Zr) for hydrogen evolution reaction (HER). To investigate their electrocatalytic activities, glassy carbon electrodes (GCE) were modified by drop casting the catalyst ink without using any binder. Linear sweep voltammetry (LSV) was used to test their electrocatalytic activities in 0.5 M HSO solution. Among these catalysts, Ir/CeO was found to exhibit excellent activity and superior stability. According to the polarization curves, onset potential (η) and overpotential (η@10 mA.cm) of Ir/CeO were found as -13 and -23 mV, respectively, which are lower than the values obtained for commercial 10% Pt/C catalyst. Moreover, Ir/CeO provides low Tafel slope (38.7 mV.dec), high turnover frequency (1.95 @100 mV) and high exchange current density (2.69 mA.cm) values. In addition, Ir/CeO shows superior stability even after 20 000 cycle in acidic environment (pH = 0.3) which makes Ir/CeO (2.44 wt% Ir) as a promising alternative electrocatalyst for HER.