Today, hydrogen (H 2 ) is overwhelmingly produced through steam methane reforming (SMR) of natural gas, which emits about 12 kg carbon dioxide (CO for 1 H (?12 kg-CO /kg-H ). Water electrolysis offers an alternative production, but today’s electrolyzers consume over 55 kWh electricity (>55 kWh/kg-H Electric grid-powered water would emit less CO than the SMR process when intensity grid power ...