The transmissive photocatalytic cell can achieve real-time tracking of catalyst crystal structure under illumination by optimizing the optical path design and reaction environment control. The core design concept is as follows:
1. Optimization of Optical Path Transparency
The main body of the reaction cell is constructed using high transmittance materials such as quartz or specific polymers, ensuring that incident light (such as ultraviolet light, visible light) penetrates the catalyst surface without attenuation. The design of light windows needs to balance light transmittance and chemical inertness. For example, using specific thin film materials as light windows can withstand the corrosion of reaction atmospheres (such as oxygen and carbon dioxide) while minimizing light scattering. Meanwhile, optimize the geometric structure of the optical path to ensure that the light source is incident at a specific angle, avoiding interference from reflected light on diffraction signal acquisition.
2. Precise control of reaction environment
Integrate temperature, pressure, and atmosphere regulation modules to simulate real catalytic reaction conditions. For example, achieving a high temperature environment (such as 200-800 ℃) through a heating system, introducing reactants (such as water vapor, methanol) through a gas control system, and maintaining a specific pressure (such as normal or high pressure). The reaction tank needs to have fast response capability to ensure that the fluctuation range of environmental parameters is less than ± 1 ℃, and to avoid masking the transient changes in catalyst crystal structure caused by temperature gradients.
3. In situ XRD signal acquisition
Connect the reaction cell with an X-ray diffractometer, allowing X-rays to pass through the light window and directly irradiate the catalyst sample. By adjusting the angle of the sample stage (such as the θ -2 θ linkage mode), continuous scanning of diffraction peaks can be achieved. To improve the signal-to-noise ratio, high-power X-ray sources (such as rotating anode targets) or synchrotron radiation sources can be used, and the detector position can be optimized to capture weak diffraction signals. For nanoscale catalysts, it is necessary to combine small angle X-ray scattering (SAXS) technology to simultaneously analyze changes in grain size and pore structure.
4. Dynamic data parsing and feedback
Real time processing of diffraction patterns through software, extracting parameters such as peak position, intensity, and full width at half maximum, and inverting the evolution of catalyst crystal structure. For example, tracking the crystal phase transition of iron oxide catalysts under light irradiation (such as α - Fe ₂ O3 → γ - Fe ₂ O3), or analyzing the dynamic reconstruction of active sites on the surface of titanate catalysts. By combining machine learning algorithms, a structure performance correlation model can be established to predict catalyst deactivation mechanisms or optimize reaction pathways.
Application Cases
In the study of photocatalytic water splitting, a transmissive photocatalytic cell can monitor the lattice strain and oxygen vacancy formation process of titanium dioxide catalyst in real-time under ultraviolet light irradiation. Experiments have shown that after 10 minutes of illumination, the interplanar spacing of catalyst (001) shrinks by 0.2%, corresponding to lattice distortion induced by photo generated charge carriers. This data provides a key structural basis for designing efficient photocatalysts.