[semi-extrinsic]

I don't know about their source, but on a global basis roughly 5% of H2 comes from electrolysis (any electricity source) while 95% comes from natural gas via steam methane reforming (chemical conversion using CH4, O2 and H2O to make H2 and CO2).

[seanhunt1]

Yep, this is correct! It largely depends on the country's electricity costs vs. access to natural gas. In some instances, rather than methane steam reforming, dry methane reforming is also used. Currently, almost all large-scale peroxide plants using the current technology (the anthraquinone process) are built next to natural gas reforming plants.