Several methods are employed for functionalization in catalysis, including: 1. Chemical Vapor Deposition (CVD): A technique to deposit thin films of functional materials onto a substrate. 2. Electrochemical Functionalization: Using electrochemical cells to introduce functional groups. 3. Photocatalytic Functionalization: Utilizing light to drive the functionalization process, often involving semiconductor catalysts. 4. Biocatalysis: Enzymes or microbes are used to introduce functional groups under mild conditions.