Pillaring and NiOx co-catalyst loading as alternatives for the photoactivity enhancement of K2Ti4O9 towards water splitting

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 K2Ti4O9 after pillaring with TiO2 pillars and loading of NiOx as a co-catalyst. The pillaring favored the charge carrier separation within the photocatalyst framework under illumination, whereas the NiOx co-catalyst, composed of nickel metal nanoparticles and nanostructured NiO, intensified the electronhole 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 mmol, for the pristine K2Ti4O9, to 982.0 mmol, 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, NiOx as the co-catalyst proved to be as effective as platinum and more effective than Ag and Au in this particular system.