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Summary: High energy density liquid fuel, ammonia, faces increasing interest globally as a carbon‐free energy carrier that can be transported over long distances for decentralized and remote distribution. The dominant ammonia production method, Haber‐Bosch, is both energy and carbon intensive to overcome the slow kinetics of the ammonia synthesis reaction from nitrogen and hydrogen. An early techno‐economic model for lithium mediated electrochemical ammonia synthesis at mild process conditions using feed rates of 27 metric ton/day for lithium hydroxide, 127 metric ton/day for cryogenic nitrogen and 264 metric ton/day electrolysis grade water is presented. Further analysis was carried out to analyze the energy consumption and reduction per metric ton of ammonia in comparison to electrochemical ammonia using H+ conductive membrane and small‐scale Haber‐Bosch technology. Electrochemical ammonia synthesis using lithium‐ion conductive membrane coupled with nitrogen generation by cryogenic distillation was found to be a sustainable pathway. The ammonia production cost via lithium mediated pathway was estimated to be less than $700 per metric ton and was found to be comparable with costs using traditional Haber Bosch. The environmental impact of electrochemical ammonia using the alkali group 1 metal, lithium, was also assessed from cradle to product. [ABSTRACT FROM AUTHOR]

The performance degradation and recovery of a polymer electrolyte fuel cell exposed to ammonia is described. The effect of ammonia contamination on each component of the MEA was studied using Neutron Imaging, lifetime tests, cell polarization measurements, potentiostatic measurements, and AC impedance spectroscopy. It is found that among the detrimental effects of the contaminant, mass transport and ORR kinectic are mostly affected. Reductions in electrolyte conductivity are not playing a major role in cell performance losses for the low levels of contamination studied here. Shifts in electrolyte proton activity reduce oxygen reduction reaction mixed equilibrium potential and so cell potential. In addition, cell potential might also be affected by overpotentials on the oxygen reduction reaction caused by oxidation of ammonia at cell potential above 0.7 V. It is demonstrated that cell initial performance can be recovered after contamination and ammonia-contaminated PEFC recovering mechanisms are discussed. [ABSTRACT FROM AUTHOR]

Green ammonia production is facing increasing interest on a global scale as a hydrogen carrier for power generation as well as fertilizer for food production. The conventional Haber-Bosch method for ammonia synthesis is energy demanding, requires high purity hydrogen, and is based on fossil fuels. A preliminary techno-economic model for electrochemical ammonia synthesis at near ambient pressure using feed rates of 32 metric ton/day for hydrogen and 135 metric ton/day for nitrogen is presented in this study. Various pathways using different methods for nitrogen generation and hydrogen production were investigated to gain insight into added energy savings per metric ton of ammonia. Electrochemical synthesis using electrolysis for hydrogen and cryogenic nitrogen was found to be a potentially viable pathway for green ammonia. The profitability metrics including discounted cash flow rate of return, net present value and discounted payback period were estimated to be 8%, $40 MM, and 4–6 years respectively for this pathway. The cost of electricity, conversion rate, and conversion efficiency dominate the tonnage cost of ammonia and were used to assess the feasibility of the model. A life cycle assessment was also conducted to assess the environmental impact of a well to product ammonia process. • Integrated electrochemical ammonia systems with renewable intermittent sources has. linear scalability advantages. • Energy consumption of at least 17 MWh per metric ton for electrochemical ammonia. • Number of modules decreases with current density. • Specific energy decreases as the production rate increases. [ABSTRACT FROM AUTHOR]

Sensors to detect mixtures of NO x /NH 3 are needed to monitor emissions of diesel automobiles where a selective catalytic reduction system uses an NH 3 mediated reaction to reduce NO x . We report on the application of a three electrode La 0.8 Sr 0.2 CrO 3 , Au 0.5 Pd 0.5 , Pt mixed potential sensor using yttria-stabilized-zirconia (YSZ) as a solid electrolyte to NO x /NH 3 sensing. Artificial neural networks were used to automatically decode the concentrations of NO x /NH 3 and errors of less than 15% are achieved. The optimal architecture for ANN decoding and the maximum density of training data points are also determined. The stability of the sensor was monitored by electrochemical impedance spectroscopy. The impedance associated with YSZ oxygen ion conduction and the electrochemical reactions at the three-phase interface are tracked over a period of over 100 days. [ABSTRACT FROM AUTHOR]

Highlights: [•] Mixed-potential electrochemical sensors are used to analyze diesel engine exhaust. [•] These sensors exhibit cross-interference between ammonia and hydrocarbons. [•] An array of sensors is created by varying bias currents applied to a single device. [•] Bayesian modeling is employed to infer ammonia concentrations in mixtures with propylene. [•] Minimal data acquisition requirements are investigated. [ABSTRACT FROM AUTHOR]

Abstract: The effect of trace quantities of ammonia on oxygen reduction reaction (ORR) on carbon-supported platinum catalysts in perchloric acid solutions is assessed using rotating ring disk electrode (RRDE) technique. The study demonstrates that ammonia has detrimental effects on ORR. The most significant effect takes place in the potential region above 0.7 V vs RHE. The effect is explained by the electrochemical oxidation of ammonia, which blocks Pt active sites and increases the formation of H2O2. This leads to losses in the disk currents and increments in the ring currents. The apparent losses in ORR currents may occur in two ways, namely, through the blocking of the active sites for ORR as well as by generating a small anodic current, which is believed to have a lower contribution. In addition, a detrimental effect of sodium cations in the potential range below 0.75 V vs RHE was demonstrated. This effect is most likely due to the co-adsorption of sodium cations and perchlorate anions on the Pt surface. [Copyright &y& Elsevier]

Abstract: The article details the application of commercial manufacturing methods towards the development of NO x /NH3 sensors for vehicle on-board emissions control. These sensors possess a unique mixed potential sensor design. This unique LANL (Los Alamos National Laboratory) design results in improved sensitivity, selectivity and response time over conventional mixed potential sensors incorporating a stable three-phase interface using a porous electrolyte coated over a dense electrode. A prototype gas sensing platform conducive to large-scale manufacturing and commercialization is also been presented. The observed results indicate the possibility of evolution towards a combined NO x /NH3 sensor on the same platform. Finally, critical challenges towards developing field deployable mixed potential NO x /NH3 sensors are identified and discussed. [Copyright &y& Elsevier]