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

Abstract

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.

Photocatalytic hydrogenation of acetophenone on a titanium dioxide cellulose film

“…Since the reaction rate constants for PC500 and P25 are very similar, PC500 was used for the following experiments. This selection was also based on previous experience, where PC500 showed a very good performance for photocatalytic hydrogen production as suspended photocatalyst 29 or as photocatalytic film. 15 …”

Screening of Heterogeneous Photocatalysts for Water Splitting

“…P90 is also a mixture of anatase and rutile phases but has a higher surface area of about 104 m 2 g -1 . PC105 and PC500 consist only of the anatase phase with surface areas of 80 and 270 m 2 g -1 , respectively [23]. As TiO 2 has a large bandgap energy, photocatalytic hydrogen production from water can only take place under UV irradiation.…”

“…P90 and PC105 have a higher activity than P25 but lower than PC500. Recently, Schwarze et al [23] investigated photocatalytic hydrogen production with the same TiO 2 photocatalysts using the full spectrum of a 300 W Xe lamp. They obtained the following order for the activity: PC500 > P105 P90 > P25.…”

Efficient preparation of nanocatalysts. Case study: green synthesis of supported Pt nanoparticles by using microemulsions and mangosteen peel extract

“…5,6 Synthesis of NPs by microemulsion method remains a reliable and well-studied approach because the size and shape of the NPs can be well designed and preserved inside the micelles present in the microemulsion. [7][8][9][10] In synthesizing of NPs, microemulsions are oen prepared using reductants such as borohydride (NaBH 4 ) and hydrazine (N 2 H 4 ), which are hazardous to both human and environmental health. [11][12][13] Therefore, an approach that makes use of environmentally benign, or "green", reductants in the microemulsion for NPs synthesis would render the process more sustainable.…”