Niobium, Tantalum, and Tungsten Doped Tin Dioxides as Potential Support Materials for Fuel Cell Catalyst Applications

Abstract

We report here on potential candidates based on the oxides SnO 2 , Nb 2 O 5 , Ta 2 O 5 , and WO 3 as alternative support materials for precious metal catalysts with high stability under highly acidic conditions and elevated temperatures as well as sufficient electric conductivity (EC) for application in PEMFCs. To increase the low conductivity of these wide bandgap binary oxides we investigated the mutual doping of these elements and report here on the doping of SnO 2 with W, Nb and Ta in the doping range of 0-15 mol-% metal component. Powder samples were prepared by an optimized sol-gel method based on

SnO2-supported single metal atoms: a bifunctional catalyst for the electrochemical synthesis of H2O2

“…To this end, SnO 2 has found applications in hydrogen production, fuel cells and ORR via metal doping and single metal atom systems. 49–52…”

Strong Interaction between Platinum Nanoparticles and Tantalum-Doped Tin Oxide Nanofibers and Its Activation and Stabilization Effects for Oxygen Reduction Reaction

“…For higher tantalum contents, the peak position was the same as for the undoped material. The O/Sn+Ta atomic ratio (Table 3) is lower than the expected value of 2, indicating oxygen vacancies in the tin oxide based materials [18,71], The O/Sn+Ta ratio increases as the tantalum content increases up to a value of 1.45 for 7.5 at.% Ta. This ratio never reached the expected value of 2 for stoichiometric SnO2, which is compatible with the existence of oxygen vacancies.…”

“…The peak positions of Sn 3d5/2 and Sn 3d3/2 (486.6 and 495.0 eV) and spin-orbit splitting of 8.4 eV correspond to Sn(IV) [52,70]. The presence of Sn 2+ on the material surface cannot nevertheless be excluded [49], due to the intrinsically oxygen-deficient structure of SnO2 [18,71]. Considering the binding energies of the doublets (230.4 and 242.0 eV) and the spin-orbit splitting at 11.6 eV, the Ta 4d5/2 and Ta 4d3/2 peaks can be assigned to Ta(V) [72].…”

“…Electrocatalysts deposited on nanostructured transition metal oxides have demonstrated high electrochemical stability at high potential [8][9][10][11][12] with good electroactivity, which was attributed to their strong electronic interaction with these supports [13][14][15]. Tin oxide has been widely considered as an alternative to carbon [16,17] due to its high conductivity compared to other metal oxides, due to the presence of oxygen vacancies and non-stoichiometric SnO2-δ [18]. In order to increase its conductivity, tin oxide is mostly employed in composites with carbon e.g.…”

“…This leads to decrease in the surface area of the support with subsequent sintering and detachment of the catalyst particles. , The search for corrosion-resistant materials meeting the electrocatalyst support requirements, including high electrical conductivity, porosity, and surface area, represents a great challenge for the development of durable PEMFC cathodes. With this aim, a range of materials and chemical compositions have been investigated, from graphitized carbons and conducting polymers to transition-metal nitrides, carbides, borides, and oxides. − Electrocatalysts deposited on nanostructured transition-metal oxides have demonstrated high electrochemical stability at high potential − with good electroactivity, which was attributed to their strong electronic interaction with these supports. − Tin oxide has been widely considered as an alternative to carbon , because of its high conductivity compared to other metal oxides because of the presence of oxygen vacancies and nonstoichiometric SnO 2‑δ . In order to increase its conductivity, tin oxide is mostly employed in composites with carbon, for example, as a protecting layer preserving the conductivity of the support − or n-doped with pentavalent ions including niobium − and antimony ,,,− providing an extra electron as a charge carrier.…”