Conductive Polymer with Enhanced Photocatalysis

Conductive Polymers for Enhanced Photocatalysis

• Conductive polymers (CPs) are conjugated organic structures with alternating double and single bonds and delocalized π electrons. They have unique electrochemical and optical properties and have wide applications in the field of photocatalysis.
• The photocatalytic activity of transition metal oxide semiconductors can be effectively improved by sensitizing transition metal oxides with organic conducting polymers.
• Alfa Chemistry Catalysts provides a wide range of conducting polymers with enhanced photocatalysis, including polyaniline (PANI), poly(3,4-ethylenedioxythiophene) (PEDOT), polyacetylene (PA), polypyrrole (PPy), polyfuran (PF), poly(p-phenylene vinylene) (PPV), polythiophene (PTh) and its derivatives, etc.

Mechanisms of Conductive Polymer-Enhanced Photocatalysis

• Conductive polymers enhance photocatalytic activity mainly from the following aspects:
• Enhanced separation of photoexcited charge carriers
• Expand the light absorption range
• Increase the adsorption of reactants
• Inhibit photocorrosion
• Reduce the formation of large aggregates
• After introducing CP for photocatalysis, CP acts as a photosensitizer to absorb a wide range of visible light because of the lower band gap compared to metal oxides. Excited electrons in the lowest unoccupied molecular orbital (LUMO) of the CP chain are injected into the CB of transition metal oxides such as TiO₂, which react with adsorbed water molecules to form O₂^·− radicals, while holes may react with water ·OH is formed.

Figure 1. Schematic illustration of the photocatalytic mechanism of conducting polymer-enhanced semiconductor materials [1]

Applications

• Combined with various semiconductor materials, conducting polymers are often used to prepare composite photocatalysts, which have been widely studied and applied in the fields of photocatalytic degradation of hazardous chemicals, antibacterials, photocatalytic hydrogen production, and photocatalytic water treatment.
• Photocatalytic water treatment

PANI and its composites are the most widely used CPs for photocatalysis of environmental pollutants, while dyes are the most studied organic pollutants for testing CP photocatalysis. Dye degradation is due to electrophilic attack on the chromophore center of the dye molecule. For example, Wang et al. prepared a series of polyaniline (PANI)-sensitized TiO₂ composite photocatalysts (PANI/TiO₂) for photocatalytic degradation of methylene blue (MB).

Figure 2. Temporal absorption spectral patterns of MB during the photocatalytic degradation process [2]

• Photocatalytic hydrogen production

Cadmium sulfide is widely used for photocatalytic hydrogen production because of its small band gap of 2.4 eV, which enables it to respond to visible light. However, due to the lower surface bond energy of CdS nanostructures, CdS is less stable during the photocatalytic hydrogen production reaction. The researchers investigated the effect of different conducting polymers (PANI, PPy, and poly(3,4-ethylenedioxythiophene) (PEDOT)) on the mechanism of CP@CdS core-shell nanorods. The results show that the PPY@CdS and PANI@CdS photocatalysts have a larger driving force to inject photoexcited holes into the HOMO of the conductive polymer shell, which can more effectively improve the hydrogen yield.

Figure 3. PANI@CdS for photocatalytic hydrogen production [3]

References

1. Sher Ling Lee. (2019). "Recent Developments about Conductive Polymer Based Composite Photocatalysts," Polymers 11: 206.
2. Fang Wang. (2010). "Visible-light-induced photocatalytic degradation of methylene blue with polyaniline-sensitized TiO₂ composite photocatalysts," Superlattices and Microstructures 48(2): 170-180.
3. Chao Wang. (2018). "Probing conducting polymers@cadmium sulfide core-shell nanorods for highly improved photocatalytic hydrogen production," Journal of Colloid and Interface Science 521: 1-10.