Jason Lau

Ammonia synthesis by N2 and steam electrolysis in molten hydroxide suspensions of nanoscale Fe2O3

Taking carbon out of the ammonial recipe The reaction used to make ammonia for synthetic fertilizer requires hydrogen. Nowadays, that hydrogen is stripped from methane, creating CO2 as a by-product. Licht et al. demonstrate a relatively efficient electrochemical process in which water and nitrogen react directly to form ammonia. The approach removes the need for an independent hydrogen generation step. The process takes place in molten hydroxide salt and requires a nanostructured iron oxide–derived catalyst. Although the catalyst suspension is currently only stable for a few hours, the protocol points to a way to produce ammonia from purely renewable resources. Science, this issue p. 637 An electrochemical route offers preliminary prospects for making the ammonia in fertilizer purely from renewable resources. 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.

One-Pot Synthesis of Carbon Nanofibers from CO2

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 high-yield and scalable electrolytic conversion of atmospheric CO2 dissolved in molten carbonates into CNFs. It is demonstrated that the conversion of CO2 → CCNF + O2 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.

Sungas Instead of Syngas: Efficient Coproduction of CO and H2 with a Single Beam of Sunlight.

The electrolytic coproduction of CO and H2 is achieved from air, water, and a single beam of sunlight rather than from fossil fuels. H2 and CO cosynthesis is driven by a single concentrator photovoltaic to simultaneously drive molten hydroxide and molten carbonate electrolyses. The carbon neutral process captures carbon without the need for the preconcentration of atmospheric carbon dioxide.

Molten air – a new, highest energy class of rechargeable batteries

This study introduces the principles of a new class of high-energy batteries and their fundamental chemistry is demonstrated. These molten air batteries use air, a molten electrolyte, are quasi-reversible (rechargeable), have the capability for multiple electrons stored per molecule, and have the highest intrinsic electric energy storage capacities. Here we show three examples of the new batterys electron transfer chemistry. These are the metal, carbon and VB2 molten air batteries with respective intrinsic volumetric energy capacities of 10 000 (for Fe to Fe(III)), 19 000 (C to CO32−) and 27 000 W h l−1 (VB2 to B2O3 + V2O5), compared to 6200 W h l−1 for the lithium air battery. Higher energy capacity, cost effective batteries are needed for a range of electronic, transportation and greenhouse gas reduction power generation devices. Needed greenhouse gas battery reduction applications include overcoming the battery driven “range anxiety” of electric vehicles, and increased capacity energy storage for the electric grid.

Fabrication of VB2/Air Cells for Electrochemical Testing

A technique to investigate the properties and performance of new multi-electron metal/air battery systems is proposed and presented. A method for synthesizing nanoscopic VB2 is presented as well as step-by-step procedure for applying a zirconium oxide coating to the VB2 particles for stabilization upon discharge. The process for disassembling existing zinc/air cells is shown, in addition construction of the new working electrode to replace the conventional zinc/air cell anode with a the nanoscopic VB2 anode. Finally, discharge of the completed VB2/air battery is reported. We show that using the zinc/air cell as a test bed is useful to provide a consistent configuration to study the performance of the high-energy high capacity nanoscopic VB2 anode.

Towards a Computational Model for Heat Transfer in Electrolytic Cells

—Study of the heat transfer processes is an important component in understanding the energy balance of an electrolytic cell. Computational modeling of the heat transfer is thus necessary for electrochemical analyses. This paper describes our efforts in developing a viable computational model for heat transfer, in certain green electrolytic cells that are driven by new molten salt chemistry discovered at the George Washington University. As part of our initial efforts, we model the heat transfer in a simplified electrolytic cell, and then obtain electrical equivalent networks. Of particular interest is the heat transfer in the presence of an endothermic reaction, which prevents the use of simple lumped resistor components for the electrical counterparts. In this paper, we derive closed form solutions using both the thermal and electrical forms of the model, and demonstrate their functional equivalence. We are able to show that instead of solving a second order differential equation, the electrical equivalent model allows for numerical computation of the steady state heat flow. The electrical analogue thus sets the stage for simulation of the heat transfer on parallel computers, and also enables the model to be extended for more complex structures.

An 11 Electron Redox Couple for Anodic Charge Storage: VB2

Nanochemical improvements of vanadium diboride are probed to facilitate anodic charge transfer. VB2 releases 11 electrons per molecule, via electrochemical oxidation, at a favorable, electrochemical potential. The discharge voltage is highly level throughout a deep discharge. This unusual multi-electron redox couple provides a charge capacity greater than other anodes, including more than lithium.