TLDR
Mixing platinum with gallium lets you get some of the desirable catalyst properties of platinum; with less platinum and as a liquid at lower temperatures; i.e much cheaper.
Mixing platinum with gallium lets you get some of the desirable catalyst properties of platinum; with less platinum and as a liquid at lower temperatures; i.e much cheaper.
Is gallium significantly cheaper than platinum?
Edit: For actual values (per gram), Gallium ~0.50 USD, Platinum ~33.22 USD
Platinum is quite a lot more valuable than gold, found in similar deposits, and rather rare. (you could say it is also produced from gold production waste streams and be mostly correct, it used to just be discarded long ago, but now it is very highly valued)
Platinum has quite a few industrial uses, gold is getting more attention as a store of value lately, probably lots of other more complex market forces going on as well.