title: The role of surface oxygenated-species and adsorbed hydrogen in the oxygen reduction reaction (ORR) mechanism and product selectivity on Pd-based catalysts in acid media.
abstract: Oxygen reduction reaction (ORR) is investigated on bulk PdO-based catalysts (oxides of Pd and Pd3Co) in oxygen-saturated 0.1 M HClO4 to establish the role of surface oxides and adsorbed hydrogen in the activity and product selectivity (H2O/H2O2). The initial voltammetric features suggest that the oxides are inactive toward ORR. The evolution of the ORR voltammograms and potential-dependent H2O2 generation features on the PdO catalyst suggest gradual and parallel in situ reduction of the bulk PdO phase below ∼0.4 V in the hydrogen underpotential deposition (Hupd) region; the reduction of the bulk PdO catalyst is confirmed from the X-ray photoelectron spectra (XPS) and X-ray diffraction (XRD) patterns. The potential-dependent H2O2 generation features originate due to the presence of surface oxides and adsorbed hydrogen; this is further confirmed using halide ions (Cl(-) and Br(-)) and peroxide as the external impurities.
authors.affiliation: Department of Energy Science and Engineering, Indian Institute of Technology Bombay (IITB), Powai, Mumbai, 400076, India. nmanoj@iitb.ac.in.
authors.forename: R
authors.initials: R
authors.lastname: Rahul
authors.forename: R K
authors.initials: RK
authors.lastname: Singh
authors.forename: B
authors.initials: B
authors.lastname: Bera
authors.forename: R
authors.initials: R
authors.lastname: Devivaraprasad
authors.forename: M
authors.initials: M
authors.lastname: Neergat