Highly Active TiO2 Photocatalysts for Hydrogen Production through a Combination of Commercial TiO2 Material Selection and Platinum Co-Catalyst Deposition Using a Colloidal Approach with Green Reductants

In this contribution, four different commercial TiO2 catalysts (P25, P90, PC105, and PC500) were screened for the photocatalytic production of hydrogen using ethanol as the sacrificial agent. The physico-chemical properties of the TiO2 powders were characterized by using different methods. The photocatalysts mainly vary in the ratio of anatase and rutile phases, and in the surface area. It was found that the photocatalytic activity is governed by the surface area of the photocatalyst. Pure TiO2,PC500 showed the best performance, and in comparison to P25, the activity was more than ten times higher due to its high surface area of about 270 m2 g−1. For further improvement of the photocatalytic activity, platinum nanoparticles (PtNPs) were immobilized onto TiO2,PC500 using two methods: a colloidal approach and a photodeposition method. For the reduction of the platinum salt precursor in the colloidal approach, different green reducing agents were used in comparison to ascorbic acid. The obtained platinum nanoparticles using natural reductants showed a higher photocatalytic activity due to the formation of smaller nanoparticles, as proven by transmission electron microscopy (TEM). The highest activity was obtained when mangosteen was used as the green reducing agent. Compared to ascorbic acid as a classical reducing agent, the photocatalytic activity of the Pt@TiO2,PC500 prepared with mangosteen was about 2–3 times higher in comparison to other as-prepared photocatalysts. The Pt@TiO2,PC500 catalyst was further studied under different operating conditions, such as catalyst and sacrificial agent concentration.

Towards Computer-Aided Graphene Covered TiO2-Cu/(CuxOy) Composite Design for the Purpose of Photoinduced Hydrogen Evolution

In search a hydrogen source, we synthesized TiO2-Cu-graphene composite photocatalyst for hydrogen evolution. The catalyst is a new and unique material as it consists of copper-decorated TiO2 particles covered tightly in graphene and obtained in a fluidized bed reactor. Both, reduction of copper from Cu(CH3COO) at the surface of TiO2 particles and covering of TiO2-Cu in graphene thin layer by Chemical Vapour Deposition (CVD) were performed subsequently in the flow reactor by manipulating the gas composition. Obtained photocatalysts were tested in regard to hydrogen generation from photo-induced water conversion with methanol as sacrificial agent. The hydrogen generation rate for the most active sample reached 2296.27 µmol H2 h−1 gcat−1. Combining experimental and computational approaches enabled to define the optimum combination of the synthesis parameters resulting in the highest photocatalytic activity for water splitting for green hydrogen production. The results indicate that the major factor affecting hydrogen production is temperature of the TiO2-Cu-graphene composite synthesis which in turn is inversely correlated to photoactivity.