An overview of metal oxide materials as electrocatalysts and supports for polymer electrolyte fuel cells

Abstract

In this review, we discuss the use of binary and multi-component metal oxides as independent electrocatalysts, co-catalysts and supports for various anode oxidation and cathode reduction reactions in polymer electrolyte fuel cells.

Effect of Mo incorporation on the electrocatalytic performance of Ti–Mo mixed oxide–carbon composite supported Pt electrocatalysts

“…In our case one may expect that during the CV measurements intercalation of hydrogen into non-incorporated, segregated MoO x oxide phase can result in a non-stoichiometric molybdenum hydrogen bronze H y MoO x formation [7]. Hou et al [17] proposed that hydrogen and CO spillover occur on H x MoO 3 , which leads to the facile removal of CO by the active water bound on the H x MoO 3 in accordance with the bifunctional mechanism.…”

“…According to the bifunctional mechanism the adsorbed hydroxyl species (OH ads ) on oxophilic molybdenum is responsible for increased CO tolerance of the Mo-containing catalysts at very low electrode potentials [7,37]. Formation of surface hydroxyls are shown schematically by equation 1:…”

“…Furthermore, in acidic solutions molybdenum hydrogen bronze H y MoO x could be formed by the "spillover" of hydrogen from Pt sites to Mo, that may have a contribution to enhanced catalytic activity toward CO electrooxidation [7,18]:…”

“…highly corrosion resistant across the anticipated potential/pH window experienced in fuel cell electrodes. Titanium dioxide is promising candidate as catalyst support in PEMFC because TiO 2 has very good chemical stability in acidic and oxidative environments [6,7]. However, undoped TiO 2 oxide is an n-type semiconductor with low electron conductivity and doping with transition metals (e.g., W, Nb and Ta) has been used to enhance its electrical conductivity [8][9][10][11].…”

Graphene-based transition metal oxide nanocomposites for the oxygen reduction reaction

“…Transition metal oxides have been intensively studied to be widely used in various fields. In addition to its well-known superiority, the other predominant characteristics of transition metal oxides for their groundbreaking application in the ORR should be highlighted: (1) abundant hydroxyl groups are inserted on the surfaces of transition metal oxides, which could be further functionalized by genetic materials (DNA and RNA) for biological catalysts; 11 (2) crystalline construction of transition metal oxides often have strong interactions, which could prevent the agglomeration of metal particles and maintain small metal particle sizes; 12,13 (3) they have considerably higher alkaline corrosion resistance in the electrochemical environment compared to noble metal and carbon-based materials due to the stabilization of the high oxidation state of transition metallic elements. In the past decade, due to excellent nanocomposite catalysts, novel advanced material-based transition metal oxides were created.…”