Pillaring and NiOx co-catalyst loading as alternatives for the photoactivity enhancement of K2Ti4O9 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 H₂ production from photocatalytic water splitting over K₂Ti₄O₉ after pillaring with TiO₂ 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 H₂ evolution from 14.9 μmol, for the pristine K₂Ti₄O₉, 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.