Hierarchical Porous TiO₂ Embedded Unsymmetrical Zinc–Phthalocyanine Sensitizer for Visible-Light-Induced Photocatalytic H₂ Production

Abstract

In this study, a novel visible-light-driven photocatalyst was designed based on unsymmetrical zinc− phthalocyanine photosensitizer on hierarchical porous TiO 2 (HPT) semiconductor. The HPT material has been prepared by a simple self-formation route. The present work successfully uses zinc phthalocyanine with spectral response extended to 700 nm triggers light harvesting center and HPT semiconductors for high photocatalytic H 2 production. This novel unsymmetrical zinc−phthalocyanine (PCH001) containing three tert-butyl and two carboxylic acid groups that act as "push" and "pull" electron transfer properties from the excited dye to the TiO 2 conduction band. The carboxylic group in the sensitizer serves as an anchoring group on to the surface of TiO 2 and to provide intimate electronic coupling between its excited-state wave function and the conduction-band manifold of the semiconductor. The excellent photophysical properties was governed further by choosing three tert-butyl groups which tuned the LUMO level of the sensitizer that provides directionality in the excited state in addition to low aggregation and high solubility. The Zn-PCH@TiO 2 composites exhibited promising activity and enhanced stability a photocatalytic system for visible-light-induced hydrogen production from water. The photocatalyst (HPT-0.25) shows H 2 production yield 2260 μmol and high turnover number (TON 18080) under visible/near IR light irradiation. Moreover, HPT-0.25 photocatalyst shows a broad visible/NIR light responsive range (400−800 nm) with high apparent quantum yields (AQY) of 7.15, 2.70, 11.57, 3.90, and 0.50% under λ = 420, 550, 690, 730, and 800 nm monochromatic light irradiation, respectively. The present work gives a new advance toward efficient solar energy conversion with promising visible/near IR light-driven photocatalytic activity.

Effect of Metal Work Function on Hydrogen Production from Photocatalytic Water Splitting with MTiO2 Catalysts

“…Photocatalytic water splitting is a promising approach to produce hydrogen from water by harnessing solar energy. Semiconductor (SC) TiO 2 is widely used for this purpose due to its high efficiency in the ultraviolet region, low cost, non‐toxicity, and high stability . In order to facilitate the water‐splitting reaction, the conduction band minimum edge of semiconductor oxides should be lower than the H + /H 2 reduction potential (0 V vs. NHE) and the valence band maximum edge must be higher than the H 2 O/H 2 oxidation potential (+1.23 V vs. NHE) .…”

Dimension‐Matched Zinc Phthalocyanine/BiVO4 Ultrathin Nanocomposites for CO2 Reduction as Efficient Wide‐Visible‐Light‐Driven Photocatalysts via a Cascade Charge Transfer

“…[15,16] However,i ti sh ard to further extend the absorption range since the optical absorption band of g-C 3 N 4 is much wider than that of BiVO 4 . [17,18] Expectedly,i t would both extend the visible-light absorption and greatly enhance the charge separation. [17,18] Expectedly,i t would both extend the visible-light absorption and greatly enhance the charge separation.…”

“…Fortunately,m etal phthalocyanines (MPc) are analogous to light-harvester chlorophyll with ap orphyrin ring, and its conjugated macrocycle structure is favorable to build adimension-matched interface with 2D-BiVO 4 .T hese inspired us to select MPc to construct aw ide-visible-light-responsive artificial Z-scheme system with BVNS,o wing to their characteristic visible/near-infrared selective absorption regions and the matched energy band alignments (the HOMO energy levels of MPc are close to the CB of BiVO 4 ). [17,18] Expectedly,i t would both extend the visible-light absorption and greatly enhance the charge separation.…”

A review on the progress of nanostructure materials for energy harnessing and environmental remediation

“…Its limitation is that it is naturally activated by UV radiations which form a very low percent of solar spectrum [228]. [229].…”