Electronically Integrated Mesoporous Ag–TiO₂ Nanocomposite Thin films for Efficient Solar Hydrogen Production in Direct Sunlight

Abstract

The synthesis of mesoporous TiO 2 by a solution-based assembly process and Ag/TiO 2 nanocomposites is provided. The efficacy of Ag/TiO 2 nanocomposite as photocatalyst in thin-film form is demonstrated for solar hydrogen generation in sunlight. Integration of Ag with TiO 2 dramatically enhanced the H 2 production: with 1 wt% Ag on TiO 2 (TiAg-1), the H 2 yield was observed to be 4.59 mmol h À1 g À1 , which is 2.3 (30) times larger than 0.5 wt% Ag on TiO 2 . TiAg-1 shows 4.3 times higher activity in film form compared with its powder counterpart. High photocatalytic efficiency is attributed to the surface plasmon resonance effect of Ag, electronic integration of Ag with TiO 2 , and subsequent valence band broadening, large distribution of Ag nanoparticles and abundant Ag-TiO 2 Schottky junctions, and the later minimizes electron-hole recombination. Interparticle mesoporous network increases necking and the high surface area offers easy accessibility of the reactants to a large number of active sites.

Aqueous Methanol to Formaldehyde and Hydrogen on Pd/TiO2 by Photocatalysis in Direct Sunlight: Structure Dependent Activity of Nano-Pd and Atomic Pt-Coated Counterparts

“…Furthermore, we compared the thin film activity with conventional testing approach with 25 mg of powder and activity values suggest that the thin film form definitely outperforms its powder counterpart. These results are consistent with earlier reports on Pd/TiO 2 , mesoporous Ag/TiO 2 , graphene, and high surface area carbon based PdAu/TiO 2 , NiFe/TiO 2 , and CuNi/TiO 2 catalyst systems. − The reason for the high activity with thin films is ascribed to effective light absorption and possible internal scattering within the film, which induces more charge carrier generation and therefore more hydrogen production compared to powder counterparts, where light scattering, rather than light absorption, is prevalent. − In the case of thin films, local utilization of charge carriers occurs within a few hundred nm 2 distance and leads to better hydrogen generation. This is, in fact, in contrast to solar cells where the charge carriers need to travel several microns to reach the back contact or current collector.…”

“…Evolved H 2 was analyzed periodically with an Agilent 7890A gas chromatograph (GC) equipped with a thermal conductivity detector (at 200 °C). Apparent quantum yield (AQY) was calculated for all the thin film catalysts, and the procedure for the same is described in our publications. ,, Methanol oxidation to C1-oxygenates was followed by HPLC analysis. Similar conditions are followed for all the target reaction studies with prepared catalyst systems.…”

“…However, the prevalent light scattering with powder suspension of the catalyst under light irradiation leads to low activities. , To overcome this issue, the thin film form of powder counterparts are employed with much higher activity compared to powder counterparts. Enhanced light absorption and hence a greater number of charge carriers helps for efficient hydrogen generation; this is established with various photocatalyst systems such as Pd/P25, mesoporous Ag/TiO 2 , PdAu/graphene/P25, CuNi/P25, and NiFe/P25. − …”

Solar-Driven Photocatalytic Films: Synthesis Approaches, Factors Affecting Environmental Activity, and Characterization Features

“…When a semiconductor is brought near a grafted metal, it encounters these intense electric fields, leading to the rapid formation of e --h + pairs in the semiconductor. Such phenomena have been exploited successfully in films activated by sunlight by using Cu [45], Au [46][47][48], and Ag [49][50][51]. It is worth noting that the electromagnetic near field at the plasmon resonance decreases rapidly, within 100 nm [52] from the plasmonic metal surface, effectively promoting surface reactions rather than generating charge carriers in the bulk of the material.…”

Multifunctional Na-enriched Ni–Fe/Ni–P plates for highly efficient photo- and electrocatalytic water splitting reactions

“…The apparent quantum yield calculation for water splitting was done using the reported equation as follows: 76 AQY % ð Þ ¼ 2  number of hydrogen molecules Number of incident photons  100…”