n-type ZnO-based semiconducting materials are increasingly studied for thermoelectrics (TE) in the past due to their inexpensive and non-toxic nature coupled with their high Seebeck coefficient and stability at elevated...

Highly ordered mesoporous niobium-doped TiO2 with a single-crystalline framework was prepared by using silica colloidal crystals with ca. 30 nm in diameter as templates. The preparation of colloidal crystals composed of uniform silica nanoparticles is a key to obtain highly ordered mesoporous Nb-doped TiO2 . The XPS measurements of Nb-doped TiO2 showed the presence of Nb(5+) and correspondingly Ti(3+) . With the increase in the amount of doped Nb, the crystalline phase of the product was converted from rutile into anatase, and the lattice spacings of both rutile and anatase phases increased. Surprisingly, the increase in the amount of Nb led to the formation of plate-like TiO2 with dimpled surfaces on one side, which was directly replicated from the surfaces of the colloidal silica crystals.

For polymer electrolyte fuel cell cathodes, highly durable supports are required to prevent catalyst degradation in supports. In this study, as model Pt catalysts, 2-10 wt% Pt was deposited on Magnéli-phase niobium-doped macroporous Ti 4 O 7 (Nb-Ti 4 O 7 ) mounted on glassy carbon rods using the coaxial arc plasma deposition method. The morphologies of 2, 5, and 10 wt% Pt catalysts showed the hemisphere fine particles, islands with ca. 1.4 nm diameter and ca. 2.4 nm thickness, and films with ca. 3.3 nm thickness, respectively. During start/stop accelerated durability tests (ADTs) of 5000 cycles following the Fuel Cell Commercialization Conference of Japan protocol, Pt was slightly agglomerated; consequently, the morphologies of the 2, 5, and 10 wt% Pt catalysts were island-like with 3.5 nm thickness, chain bead-like with 4 nm thickness, and film-like with 4 nm thickness, respectively. This slight agglomeration led to good durability during the ADTs. Herein, the oxygen reduction reaction (ORR) mass activity (MA) values at 0.9 V vs. reversible hydrogen electrode (RHE) of the 2, 5, and 10 wt% Pt catalysts were 79, 60, and 36 A g À1 Pt after 5000 cycles ADT, respectively, which had declining ratios after 5000 cycles were 32 %, 17 %, and 0 %, respectively. The island-like and film-like Pt/Nb-Ti 4 O 7 presented activity and durability comparable to a Pt/C catalyst, which was 42 A g À1 Pt (0.9 V vs. RHE) with a 12 % of declining ratio after the ADTs. The durability of the MA suggested that the different affinity caused by different crystal faces led to the slight agglomeration of 2, 5, and 10 wt%_Pt/Nb-Ti 4 O 7 catalysts. These catalysts showed electrochemical surface areas (ECSAs) of 36, 27, and 29 m 2 g −1 after the ADTs, with declining ratios as low as 20 %, 6 %, and 0 %, respectively. All Pt/Nb-Ti 4 O 7 catalysts showed higher durability of the ECSAs than the Pt/C catalyst, which was 68 m 2 g −1 with a 30 % declining ratio after the ADT. Different from common Pt nanoparticle catalysts, which agglomerate into large spherical Pt particles, the slight agglomeration was caused by the interconnection of the deposits and supplemented by a limited increase in the diameter or thickness. The island-like morphology of Pt with a limited thickness presented both high durability and activity among the Pt/Oxide catalysts.

Ordered mesoporousA uw as prepared using double gyroid (cubic Ia-3d)m esoporous silica KIT-6 as at emplate. The Au frameworks were formed within the template via as eed-mediated growth process. Au nanoparticles were initially prepared as seeds within the mesopores, and subsequently,t hey were grown under mild andc ontrolled reducing conditions. The transmission electron micrographs and scanning electron micrographs of mesoporous Au after the removal of the template revealed the formation of mesoporous Au replicas. The small-angle X-ray scattering pattern of mesoporousA ur eveals that the obtained mesoporousA u has ac ubic I4 1 32 mesostructure, whichi sd ifferent from that of the originalt emplate, implying that Au was deposited within only one mesochannel of the two interconnected ones. The seed-mediated growth process is ak ey factor in the successful formation of orderedm esoporous Au using a mesoporouss ilica template. Our preparative methodc an serve as ag uide for furtherd evelopment of synthetic and materials chemistry of mesoporousAu.