I need to make a very simple and small ph sensor like the title.

I read a few related papers, but I don't understand 100%, so I have no idea where to start.

(https://www.youtube.com/watch?v=GmaGTEU8I4A)

In this video 3:20, an indicator electrode is made of platinum wire and IrO2, and the reference electrode is made by drop-cating F2Cl3 and MCH onto the silver wire.

1. Why is MCH dropcasting at reference electrode?

2. Also, how to clean the platinum wire ??

3. If there is a way to make the ph sensor easier and cheaper than the method in the video, please let me know

Thanks for reading.