While PoS with an unlimited supply (much alike the currently prevalent Fiat system) could work, PoS with a capped supply is a certain way to doom.

If you want energy efficiency, decentralization, distribution fairness and scaling there is - at least for the time being - only one coin to look into.

https://www.burstcoin.ist/2017/10/30/going-further-a-poc-and-pos-comparison/