Nanocrystalline mesoporous Ta 2O 5-based photocatalysts prepared by surfactant-assisted templating sol–gel process for photocatalytic H 2 evolution

Abstract

Nanocrystalline mesoporous Ta 2O 5 photocatalyst was synthesized through a combined sol–gel process with surfactant-assisted templating mechanism under mild conditions. Controlled hydrolysis and condensation of tantalum pentaethoxide modified with acetylacetone in the presence of laurylamine hydrochloride surfactant aqueous solution ultimately yielded nanocrystalline Ta 2O 5 with mesoporous characteristic. The NiO cocatalyst loading at various contents was also performed by single-step sol–gel method, in which nickel precursor was incorporated into the completely hydrolyzed tantalum sol prior to the gelation step. The synthesized photocatalysts were methodically characterized by TG–DTA, XRD, N 2 adsorption–desorption, diffuse reflectance UV–vis spectra, SEM, and TEM analyses. The XRD patterns indicated that the cocatalyst was in a very high dispersion degree on mesoporous Ta 2O 5. N 2 adsorption–desorption isotherms and SEM observation verified that the photocatalysts possessed mesoporous structure. The surface area of the samples from BET method was quite high with very narrow monomodal pore size distribution estimated from BJH method. The photocatalytic performance of the materials was assessed via H 2 evolution from water using methanol as a hole scavenger under UV light irradiation. For unloaded Ta 2O 5 photocatalysts, the sample calcined at 700 °C showed the highest photocatalytic H 2 evolution activity. Moreover, the photocatalytic activity of such the sample was dramatically increased with the cocatalyst loading, exhibiting the optimum loading content at 5 wt.%.