Investigation of Mesoporous Niobium-Doped TiO₂as an Oxygen Evolution Catalyst Support in an SPE Water Electrolyzer

Abstract

Titania doped by niobium was successfully synthesized via a modified evaporation-induced self-assembly method (EISA) as a support of IrO 2 for a solid polymer electrolyte water electrolyzer (SPEWE). The doping amount of niobium (5, 10, 20 at. %) was emphatically investigated to evaluate the effects on nanostructure, morphology, and oxygen evolution reaction (OER) activity of Nb-doped titania supported IrO 2. The high-resolution transmission electron microscopy (TEM) results show that IrO 2 supported by Nbdoped titania exhibits grain refinement and uniform dispersion. An investigation of the electrocatalytic activity by half-cell electrochemical testing reveals that the Nb-doped titania supported IrO 2 catalyst demonstrates significant OER activity. When the Nb content reaches 20 at. % in the support, the Nb-doped titania supported IrO 2 possesses the highest OER activity, which is superior to that of pristine titania supported IrO 2 and unsupported IrO 2 . The single-cell tests also prove that 20 at. % is the best Nb doping amount for titania supports of IrO 2 . It is found that the majority of the OER activity increase is due to the Nb-doping induced enhancement of the specific surface area and surface activity of transferring charge and species. The additional specific surface area and redox couples of Nb(IV)/Nb(V) are also responsible for this performance enhancement. Herein, the as-synthesized Nb-doped titania is considered to be a promising oxygen evolution catalyst support for SPEWE applications.

Activity of IrO2 supported on tantalum-doped TiO2 electrocatalyst for solid polymer electrolyte water electrolyzer

“…Firstly, Ta-doped TiO 2 were prepared by an evaporation-induced self-assembly method (EISA), which was effective for the synthesis of mesoporous niobium-doped TiO 2 with a high specic surface area 11 and denoted as Ti 1Àx Ta x O 2 , where x (0.05, 0.1, 0.2, 0.3) accorded with the molar percent content of Ta. Then, the resultant powder was annealed under a strong reducing atmosphere.…”

Oxygen‐Deficient Ti0.9Nb0.1O2‐x as an Efficient Anodic Catalyst Support for PEM Water Electrolyzer

“…The peaks at approximately 54.3°, 69.0° and 69.8° are matched with the (211), (301) and (112) planes of tetragonal rutile (JCPDS 21‐1276), indicating the prepared TiO 2 is a mixture phases of tetragonal anatase and rutile. The XRD pattern of IrO 2 /TNO (Figure ) displays similar shape with IrO 2 /TiO 2 and no diffraction peaks from Nb or Nb compounds are examined, indicating that the Nb ions were successfully doped into titania lattice . For IrO 2 /TNO−Hx (x=600, 750, 900) samples (Figure ), the emerging peaks at approximately 39.1°, 41.2°, 44.0° and 64.0° are matched with the (200), (111), (210) and (310) planes of tetragonal rutile (JCPDS 21–1276).…”

“…The specific surface area of unsupported IrO 2 is only 62.4 m 2 g −1 resulted from its serious particle aggregation, and the BJH average pore size is 5.6 nm. The specific surface area of IrO 2 /TNO (215.6 m 2 g −1 ) is higher than that of IrO 2 /TiO 2 (169.4 m 2 g −1 ) because of Nd doping . Compared with the IrO 2 /TNO sample, the specific surface area values of IrO 2 /TNO−Hx samples decrease from 215.6 to 198.5, 126.1, 101.6 m 2 g −1 corresponding to IrO 2 /TNO−H600, IrO 2 /TNO−H750, IrO 2 /TNO−H900 samples, respectively.…”

“…Compared with the IrO 2 /TNO sample, the specific surface area values of IrO 2 /TNO−Hx samples decrease from 215.6 to 198.5, 126.1, 101.6 m 2 g −1 corresponding to IrO 2 /TNO−H600, IrO 2 /TNO−H750, IrO 2 /TNO−H900 samples, respectively. The BJH average pore sizes of IrO 2 /TiO 2 , IrO 2 /TNO, IrO 2 /TNO−H600, IrO 2 /TNO−H750 and IrO 2 /TNO−H900 are 11.8, 11.2, 11.6, 12.5, and 12.8 nm, which are effective for mass transfer in OER . The decrease of specific surface area for IrO 2 /TNO−Hx samples may be attributed to the gradually accelerate aggregation of TNO particles with the increasing of hydrogenation temperature, as observed by TEM analysis…”

“…One way to improve the electrical conductivity of TiO 2 support is doping foreign elements. Our group has studied the effect of foreign elements (such as V, Nb, Ta) doped TiO 2 support on the physical and catalytic property of catalysts, and a superior electronic conductivity and catalytic activity had been achieved than that of bare TiO 2 support. Among the foreign elements, Nb doped TiO 2 has been widely studied due to the remarkable enhancement of electronic conductivity (0.2–1.5 S cm −1 ) .…”