Photocatalytic reduction of Cr(VI) within mesoporous TiO₂ templated and confined with chlorophyll

Abstract

Biomimetic light-harvesting architecture has been proposed as an alternative for existing solar conversion systems. Chlorophyll-sensitized TiO 2 have been identified as promising catalyst for photocatalytic reduction system, but it is largely limited to complicated process for purification of chlorophyll and adding extra hole scavenger in system. In sharp contrast to conventional photosensitization methods in which the organic dyes were often adsorbed after photosensitization, herein mesoporous TiO 2 incorporated with chlorophyll extract was synthesized in situ (TiO 2 /Chl). Interestingly, TiO 2 incorporated with chlorophyll exhibited two distinct absorption bands around 407 and 668 nm which are closed to the characteristic absorption peak of chlorophyll. TiO 2 incorporated with chlorophyll kept at 185 • C for 1.5 hours (TiO 2 /Chl-185) achieved a high photoreduction rate of 86.1% for the photocatalytic reduction of Cr(VI), which was approximately 29 and 20 times higher than that of TiO 2 and TiO 2 adsorbing chlorophyll (TiO 2 /ads Chl), respectively. The significant enhancement was due to the confinement of chlorophyll. This demonstrates that mesoporous TiO 2 templated and confined with chlorophyll could offer a new approach for synergistic photoreduction of Cr(VI).

Double S‐Scheme Polydopamine/TiO2/Chlorophyll as Stable and Efficient Green Photoelectrocatalyst

“…Although, the Chl-a solution stability in the natural environment was demonstrated (see Figure 2, c), it seems that the interaction between the hydrophobic Chl coating and hydrophilic NT surface is weak resulting in photocatalyst instability and poor performance in time. This observation is in accordance with other studies [47,62] and results demonstrate that dye-sensitized photocatalysts had low photo-stability and that surfactants or other chemicals should be used to stabilize the photosensitive function of the photocatalysts. [63] As shown in Figure 12a, the presence of PD on NT leads to a reduced but constant current density, which is an indication that the NT/PD surface has an increased level of stability.…”

Biotemplated heterostructure materials: opportunities for the elaboration of new photocatalysts and selective-oxidation catalysts

“…Natural rubber latex is usually grown in sufficient sunlight. Like other green plants, rubber trees can be seen as a plant factory of solar energy; therefore, natural latex has good application prospects in the synthesis of efficient solar photocatalysts, 73–75 although there have been some reports using a series of latex templates as template preparation catalyst materials. For example, a composite hollow sphere with a complex structure was successfully synthesized by using hollow latex cages (HLCs) as a template for the sol–gel method, 76 as shown in Fig.…”

“…Using natural rubber latex as a biological template, we synthesized cobalt-doped mesoporous alumina (Co/MAl 2 O 3 ) and employed it as a catalyst for the oxidation of tetralin. 73 Under mild conditions, this catalyst has demonstrated exceptional efficiency in the conversion of tetral into tetralone, marking a significant achievement. With an impressive substrate conversion rate of 80.3% and a remarkable selectivity of 74.5% towards tetralone, it has outperformed other catalysts, including cobalt-doped mesoporous silica synthesized using natural latex as a template (Co/MSiO 2 /RL) and cobalt-doped alumina synthesized using the traditional chemical template P123 (Co/MAl 2 O 3 /P123).…”