US hydrogen company Plug Power Inc (<a href="https://www.nasdaq.com/market-activity/stocks/plug" target="_blank">NASDAQ:PLUG</a>) and chlor alkali firm Olin Corporation (<a href="https://www.nyse.com/quote/XNYS:OLN" target="_blank">NYSE:OLN</a>) have commissioned a 15-tonne-per-day liquid hydrogen plant in St Gabriel, Louisiana.