Pillaring and NiO X co-catalyst loading as alternatives for the photoactivity enhancement of K 2 Ti 4 O 9 towards water splitting

Abstract

Structural improvements of efficient and abundant photocatalysts and the employment of less expensive co-catalysts are appealing routes to promote the development of economically viable solar fuel production. We herein report a significant enhancement of the H 2 production from photocatalytic water splitting over K 2 Ti 4 O 9 after pillaring with TiO 2 pillars and loading of NiO x as a co-catalyst. The pillaring favored the charge carrier separation within the photocatalyst framework under illumination, whereas the NiO x co-catalyst, composed of nickel metal nanoparticles and nanostructured NiO, intensified the electron-hole separation at the surface. These are unprecedented results indicated by surface photovoltage spectroscopy, which was applied for the first time in this kind of photocatalyst composite. All modifications enhanced the H 2 evolution from 14.9 μmol, for the pristine K 2 Ti 4 O 9 , to 982.0 μmol, for the final product, after 7 h of irradiation tests using methanol as a hole scavenger. This boost was also favored by the mesoporosity and high surface area created by the pillaring process. Moreover, NiO x as the co-catalyst proved to be as effective as platinum and more effective than Ag and Au in this particular system.