Titanium-Niobium Oxides as Non-Noble Metal Cathodes for Polymer Electrolyte Fuel Cells

Abstract

Abstract:In order to develop noble-metal-and carbon-free cathodes, titanium-niobium oxides were prepared as active materials for oxide-based cathodes and the factors affecting the oxygen reduction reaction (ORR) activity were evaluated. The high concentration sol-gel method was employed to prepare the precursor. Heat treatment in Ar containing 4% H2 at 700-900 °C was effective for conferring ORR activity to the oxide. Notably, the onset potential for the ORR of the catalyst prepared at 700 °C was approximately 1.0 V vs. RHE, resulting in high quality active sites for the ORR. X-ray (diffraction and photoelectron spectroscopic) analyses and ionization potential measurements suggested that localized electronic energy levels were produced via heat treatment under reductive atmosphere. Adsorption of oxygen molecules on the oxide may be governed by the localized electronic energy levels produced by the valence changes induced by substitutional metal ions and/or oxygen vacancies. OPEN ACCESSCatalysts 2015, 5 1290

Electrocatalysis in Fuel Cells

“…Non-noble metal oxides and chalcogenides are also promising catalysts for ORR. Some interesting works on the synthesis and evaluation of Ti-Nb oxides [15], CoS [16] and FeSe2 [17] were also included in this Special Issue.…”

Nanometric Fe-Substituted ZrO2on Carbon Black as PGM-Free ORR Catalyst for PEMFCs

“…21 One strategy to increase their ORR activity is to increase the density of oxygen vacancies or uncoordinated metal sites, hypothesized to be sites with higher ORR activity. [22][23][24] In this respect, Ishihara et al 25 have already claimed enhanced ORR activity for titanium-niobium oxides (prepared by a sol-gel method), showing that the strength of oxygen interaction with the oxide surfaces could be tuned by substitutional ions (here, Nb in TiO 2 ) causing valence changes and/or oxygen vacancies. Creation of oxygen vacancies in bulk ZrO 2 by substitution of Zr 4+ by Fe 3+ has been reported by Sangalli et al 26 In their study, they use both theoretical (density functional theory, DFT) and experimental approaches (synthesis of Fe-doped ZrO 2 thin films) to prove the formation of oxygen vacancies by Fe 3+ doping into the ZrO 2 lattice.…”

Synthesis of Fe, Co Incorporated in P-Doped Porous Carbon Using a Metal-Organic Framework (MOF) Precursor as Stable Catalysts for Oxygen Reduction Reaction

“…However, due to its expensive cost, poor durability, and CO poisoning in the reaction, 1-5 the need to explore new efficient, durable, and cheap catalysts to substitute the Pt/C is urgent. In past decades, several alternatives have been developed, such as noble metal-based nanoparticles, 5,6 non-noble metal catalysts, 7,8 and metal-free materials. 9 Heteroatom-doped carbon materials are the representatives of the metal-free materials and the mechanism of the reduction of oxygen has been widely investigated.…”