Comparative study of catalytic activities among transition metal-doped IrO 2 nanoparticles

• Published in: Scientific reports 2018-11, Vol.8 (1), p.16777
• Main Authors: Lee, Hangil, Kim, Joo Yeon, Lee, Si Young, Hong, Jung A, Kim, Namdong, Baik, Jaeyoon, Hwang, Yun Jeong
• Format: Article
• Language: English
• ISSN: 2045-2322

Catalytic activities of transition metal-doped IrO nanoparticles (TM-IrO NPs; TM = Cr, Mn, Fe, Co, or Ni) are compared for various oxidation reactions such as electrochemical oxygen evolution reaction (OER), gas-phase photo-oxidation of thiol function group, and CO oxidative conversion. Here, we discovered a series of TM-IrO catalysts have a common activity trend for these oxidation reactions, and their activities are closely related with modified electronic states of IrO , strongly affected by the types of the transition metal across the periodic table. For all oxidation reactions, Cr- and Mn-IrO achieved the highest oxidation catalytic activity, and sequentially decreased activities were obtained with Fe, Co, and Ni doped IrO . For instance, the highest OER activity was achieved by Cr or Mn doping exhibiting the smallest overpotential η = 275~230 mV at 10 mA/cm , while Ni-IrO showed rather larger overpotential (η = 347 mV) even compared with non-doped IrO (η = 314 mV). Scanning transmission X-ray microscopy and high-resolution photoemission spectra of TM-IrO indicated dopant metals modified the Ir-O interaction and thus increasing oxygen vacancy defects in IrO . Strongly positive correlation was observed between the catalytic activities and vacancy states. The amount of defect related signals was observed the most for Cr- or Mn-IrO , less so for Fe- or Co-IrO , and unnoted for Ni-IrO compared with bare IrO . Based on these catalytic activities and surface spectroscopic analysis results, vacancy defects induced by doping in TM-IrO NPs are proposed to contribute to enhance the oxidation activities.