Band gaps - Catalysis

What is a Band Gap?

A band gap is the energy difference between the valence band and the conduction band in a solid material. It is a crucial parameter in determining a material's electrical conductivity. In the context of catalysis, band gaps play a vital role in semiconductor-based catalysts, particularly in photocatalysis.

Why is the Band Gap Important in Catalysis?

The band gap determines the wavelengths of light that a semiconductor can absorb and convert into chemical energy. This property is essential for processes like photocatalytic water splitting and photocatalytic degradation of pollutants. A smaller band gap means the material can absorb visible light, while a larger band gap restricts absorption to ultraviolet light.

How Does the Band Gap Influence Catalytic Activity?

The catalytic activity of a semiconductor is highly dependent on its band gap. A smaller band gap can lead to higher photocatalytic efficiency because it allows the material to harvest more sunlight. However, too small a band gap can result in rapid recombination of electron-hole pairs, reducing efficiency. Therefore, a balance must be struck to optimize performance.

What Materials Are Commonly Used in Band Gap Engineering for Catalysis?

Titanium dioxide (TiO2) is one of the most studied materials due to its stability and strong oxidative power, but its large band gap (~3.2 eV) limits its activity to UV light. Other materials like zinc oxide (ZnO), cadmium sulfide (CdS), and graphene-based composites are also explored to tune the band gap for broader light absorption.

What Techniques are Used to Modify the Band Gap?

Several techniques are employed to modify the band gap of materials for catalytic applications:

Doping: Introducing foreign atoms into the semiconductor to create energy levels within the band gap.
Surface modification: Altering the surface properties to improve light absorption and charge separation.
Heterojunctions: Combining two different semiconductors to form a junction that enhances charge separation and extends the absorption spectrum.
Composites: Integrating materials with different band gaps to achieve a synergistic effect.

What are the Challenges in Band Gap Engineering?

Despite the potential benefits, band gap engineering faces several challenges:

Recombination: Rapid recombination of electron-hole pairs can negate the benefits of a smaller band gap.
Stability: Some materials with desirable band gaps may degrade under operating conditions.
Cost: High-quality materials and complex modification techniques can be expensive.

What are the Future Directions?

The future of band gap engineering in catalysis lies in developing new materials and techniques to achieve optimal performance. Research is ongoing in areas like perovskites, 2D materials, and quantum dots to create efficient and stable catalysts that can harness a broader spectrum of sunlight.

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Band gap engineering and photoluminescence tuning in halide double perovskites.

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A detailed study of the electronic and optical properties of germanium nanotubes.

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A Theoretical Investigation for Exploring the Potential Performance of Non-Fullerene Organic Solar Cells Through Side-Chain Engineering Having Diphenylamino Groups to Enhance Photovoltaic Properties.

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Terahertz Polarization Isolator Using Two-Dimensional Square Lattice Tellurium Rod Array.

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Experimental and Theoretical Investigations of Direct and Indirect Band Gaps of WSe.

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Evidence of Energy and Hole Transfer between 2D CdSe0.7Te0.3 Alloy NPLs with Porphyrin Molecules.

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A way to identify whether a DFT gap is from right reasons or error cancellations: The case of copper chalcogenides.

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Synthesis of Ultrawide Band Gap TeO Nanoparticles by Pulsed Laser Ablation in Liquids: Top Ablation versus Bottom Ablation.

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Nanostructured CeO photocatalysts: optimizing surface chemistry, morphology, and visible-light absorption.

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Functionalized fennel extract-mediated alumina/cerium oxide nanocomposite potentiometric sensor for the determination of diclofenac sodium medication.

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Unravelling co-catalyst integration methods in Ti-based metal-organic gels for photocatalytic H production.

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Interlayer Polymerization to Construct a Fully Conjugated Covalent Organic Framework as a Metal-Free Oxygen Reduction Reaction Catalyst for Anion Exchange Membrane Fuel Cells.

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Effective Charge Collection of Electron Transport Layers for High-Performance Quantum Dot Infrared Solar Cells.

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