From CO2 and Water
According to this sci article, they came up with a way to use waste co2 and water with an electrolitic catalyst and low voltage (10 mV) to produce plastic. Article is behined paywall https://pubs.rsc.org/en/Content/ArticleLanding/2018/EE/C8EE00936H#!divAbstract
That electrode is a "nickel phosphides" which this article talks about making. free https://pubs.acs.org/doi/abs/10.1021/acs.jpcb.7b06020
Another or possibly related article. free https://pubs.acs.org/doi/10.1021/acscatal.7b04347