Full decarbonization of transportation, industrial and, to some extent, power generation sectors is not possible without wide use of energy dense zero- or low-carbon fuels that can be easily converted to motive power, heat and electricity. Synthesis of carbon-containing fuels and ammonia from hydrogen and CO₂ and nitrogen feedstock respectively is well known. Hydrogen, currently generated from fossil fuels, can be easily replaced with electrolytic (e.g., “green”) or pyrolytic hydrogen. However, these processes are not yet economical if clean hydrogen is utilized. Several pathways to improve efficiency and reduce capital costs for both processes of hydrogen generation and hydrogen conversion to fuels including the integration with energy sources (e.g., nuclear power) or exothermic fuel synthesis will be discussed.

Potentially more promising path to renewable fuels via co-electrolysis of water and CO₂ or N₂ is still in infancy and suffers from low electric and Faradaic efficiencies. Different strategies to suppress parasitic reactions will be discussed. One of them is “tandem” electrosynthesis where electrolytic hydrogen is used without isolation in electrochemical reduction of N₂ and CO₂. Scalability and economics of combined electrochemical/chemical and pure electrochemical processes based on cost and availability of energy sources, feedstock, achievable technical parameters, and fuel transport modes will be compared.

Development of advanced pathways for electrochemical synthesis of fuels including applied and early-stage research will be illustrated with projects funded by DOE Advanced Research Projects Agency (ARPA-E) and their role in DOE Hydrogen Program and Hydrogen Earthshot will be discussed.