The Haber-Bosch process to produce ammonia for fertilizer currently relies on carbon-intensive steam reforming of methane as a hydrogen source. We present an electrochemical pathway in which ammonia is produced by electrolysis of air and steam in a molten hydroxide suspension of nano-Fe2O3. At 200°C in an electrolyte with a molar ratio of 0.5 NaOH/0.5 KOH, ammonia is produced at 1.2 volts (V) under 2 milliamperes per centimeter squared (mA cm(-2)) of applied current at coulombic efficiency of 35% (35% of the applied current results in the six-electron conversion of N2 and water to ammonia, and excess H2 is cogenerated with the ammonia). At 250°C and 25 bar of steam pressure, the electrolysis voltage necessary for 2 mA cm(-2) current density decreased to 1.0 V.

Carbon nanofibers, CNFs, due to their superior strength, conductivity, flexibility, and durability have great potential as a material resource but still have limited use due to the cost intensive complexities of their synthesis. Herein, we report the highyield and scalable electrolytic conversion of atmospheric CO 2 dissolved in molten carbonates into CNFs. It is demonstrated that the conversion of CO 2 → C CNF + O 2 can be driven by efficient solar, as well as conventional, energy at inexpensive steel or nickel electrodes. The structure is tuned by controlling the electrolysis conditions, such as the addition of trace transition metals to act as CNF nucleation sites, the addition of zinc as an initiator and the control of current density. A less expensive source of CNFs will facilitate its adoption as a societal resource, and using carbon dioxide as a reactant to generate a value added product such as CNFs provides impetus to consume this greenhouse gas to mitigate climate change.

One pathway to remove the greenhouse gas carbon dioxide to mitigate climate change is by dissolution and electrolysis in molten carbonate to produce stable, solid carbon. This study determines critical knowledge to minimize the required electrolysis energy, the reaction stoichiometry in which carbon and O 2 are the principal products, and that CO 2 can be electrolyzed inexpensively. Thermochemical and experimental results indicate that the principal carbon-deposition reaction in molten Li 2 CO 3 or Li 2 O/Li 2 CO 3 electrolytes at 750°C is Li 2 O + 2CO 2 → Li 2 CO 3 + C + O 2 . The reaction occurs at high Faradaic efficiency of the 4e − reduction of CO 2 to carbon and oxygen at an electrolysis voltage as low as <1 V. Electrolytes without lithium carbonate but containing calcium and/or barium carbonate can also be employed as reaction media for successful carbon deposition, e.g. in an Na/BaCO 3 melt. However, the electrolysis reduction in pure Na or K or Na/K carbonate eutectics at 1 atm of CO 2 forms metals and/or gases, i.e., CO.

New molten salt chemistry allows solar thermal energy to drive calcium oxide production without any carbon dioxide emission. This is accomplished in a one pot synthesis, and at lower projected cost than the existing cement industry process, which after power production, is the largest contributor to anthropogenic greenhouse gas emissions.

a b s t r a c tMolten carbonate electrolyzers offer a pathway to capture emitted CO 2 from the flue gas of the power plants and transform this greenhouse gas emission at low energy and high yield instead into a specific, value added, hollow carbon nanofiber product, carbon nanotubes. The present day value of the carbon nanotubes product is $10,000 that of proposed, or in place, current carbon tax costs of $30 per ton, strongly incentivizing carbon dioxide removal. The recent progress in high-temperature molten carbonate electrolysis systems for carbon dioxide utilization and the impact these advances have on developing a CO 2 -free fossil fuel power plant for electricity generation is presented. A thermodynamic model analysis is presented for a molten Li 2 CO 3 electrolysis system incorporated within a combined cycle (CC) natural gas power plant to produce carbon nanofibers (CNF) and oxygen. Such a CC CNF plant system is shown to require 219 kJ to convert one mole of CO 2 to carbon, and generates electricity at higher efficiency due to pure oxygen looped back to the gas turbine input from the CO 2 splitting, with the added advantages that (i) the CC CNF plant emits no CO 2 and (ii) all CO 2 is converted to value added carbon nanotubes useful for strong, lightweight construction, batteries and nanoelectronics. Converting to power and ton units, per metric ton of methane fuel consumed the CC CNF plant is thermodynamically assessed to produce 8350 kW h of electricity and 0.75 ton of CNT and emits no CO 2 , while the CC plant produces 9090 kW h of electricity and emits 2.74 ton CO 2 . The required energy balance for a carbon nanotube production from an analogous coal power plant consumes a larger fraction of the coal energy, and encourages co-generation with renewable electric energy.