A road ahead via lithium-mediated electrochemical nitrogen reduction?

Realisation of electrochemical nitrogen reduction to ammonia has proven to be a herculean scientific challenge. Recently, a focus on Lithium-mediated synthesis has delivered promising results. Last year a team from Monash University in Australia unveiled their phosphonium “proton shuttle” method, and this year have reported nearly 100% Faradaic efficiency for the reaction (with promising reaction rates). Late last year, a team from the Technical University of Demark (DTU) reported that addition of small amounts of oxygen gas drastically increased Faradaic efficiencies and production rates. The results push electrochemical synthesis R&D ever-closer to elusive benchmarks set for commercial realisation.


New Insights into Electrocatalysis of Nitrogen Reduction to Ammonia

Ammonia was electrochemically produced from nitrogen and water using a ruthenium–platinum (RuPt) alloy catalyst cathode and a nickel anode at ambient pressure and room temperature. The rate of ammonia formation was 5.1 × 10−9 gNH3 s−1 cm−2 with a 13.2% faradaic efficiency at an applied potential of 0.123 V vs. RHE; it reached 1.08 × 10−8 gNH3 s−1 cm−2 at 0.023 V. Ammonia production was investigated under selected potentials and temperatures. Real-time direct electrochemical mass spectrometric (DEMS) analysis of the evolved gases was performed at various applied potentials. In general, the mass-to-charge ratio signals of hydrogen and ammonia were detected,…


Electrochemical Nitrogen Reduction Reaction on Transition Metal Nitride Nanoparticles in Proton Exchange Membrane Electrolyzers

Transition metal nitride nanoparticles are synthesized and utilized as catalysts for electrochemical nitrogen reduction reaction (ENRR) to produce ammonia in a proton exchange membrane electrolyzer (PEMEL). The catalysts show an average ENRR rate and Faradaic efficiency (FE) of 3.3 × 10−10 mol s−1 cm−2 (6.6 × 10−10 mol s−1 mg−1) and 5.95% at −0.1 V within 1 h, respectively. Both the ENRR rate and FE are approximately two orders of magnitude higher than those of noble metal catalysts. Time-dependent results suggest that the catalytic activity of transition metal nitride nanoparticles is stable at −0.1 V, with the catalytic activity decreasing…


A Low Pressure Membrane Based Renewable Ammonia Synthesis

Ammonia is currently mostly produced by the highly energy and carbon-intensive Haber–Bosch process, which requires temperatures of 450–500 °C and pressures of up to 200 bar. The feedstock for this process is hydrogen from natural gas (NG), coal or oil, and nitrogen produced from air by cryogenic route or pressure swing adsorption (PSA). The share of NG, coal and fuel oil feedstock for the global production of ammonia is 72%, 22% and 4% respectively, contributing to approximately 420 million tons of CO2 emissions per annum, representing over 1% of global energy related emissions. The energy consumed for ammonia synthesis by…


Dense Metallic Membrane Reactor Synthesis of Ammonia at Moderate Conditions and Low Cost

Commercial ammonia synthesis relies on the Haber–Bosch process that has remained largely unchanged for a hundred years. The equilibrium constant of this exothermic reaction quickly becomes unfavorable above 200 °C, but the catalyst requires temperatures above 400 °C to have sufficient activity. To overcome these conflicting requirements the process is conducted at extremely high pressure (100 – 200 atm) using multiple passes with inter-stage cooling to achieve sufficient conversion. A cost analysis reveals the compressors needed to reach the required pressures consist of 50% the capital cost for Haber-Bosch. Therefore, a longstanding scientific challenge has been to achieve NH3 synthesis…


Design Optimization of a Distributed Ammonia Generation System

Distributed ammonia generation located near farms is a promising alternative to the current practice of large-scale, centralized production. This production mode would reduce the need for transportation of ammonia over long distances currently caused by the mismatch between production and consumption locations. In addition, a small-scale ammonia synthesis process could more easily take advantage of distributed power generation based on wind or sunlight to reduce energy costs and lessen the dependence on fossil fuels. Distributed, renewables-based fertilizer production would largely insulate farmers against market uncertainty while also increasing the sustainability of the agricultural supply chain. However, a technically proven, economically…


Load Range Enhancement of Haber-Bosch Process Designs for NH3 Sustainable Energy Storage By Multi-Parametric Optimization

With the world’s major shift towards renewable energy, the need of chemicals-based energy storage has drastically increased, as renewable energy is intermittent and energy storage medium is required. Among several chemical energy storage options, ammonia is promising for renewable energy on utility-scale. The Haber-Bosch ammonia synthesis was the first heterogeneous catalytic system employed in the chemical industry and developed over a period of century. However, the conventional ammonia process has been designed and optimized for steady state operation and high capacity. Power-to-ammonia requires a more flexible operation, small size reactors and decentralized production. The impact of adjustable parameters, such as,…


LiH Mediated Ammonia Synthesis Under Mild Condition

Having a hydrogen content of 17.6 wt% NH3 is an attractive hydrogen carrier. The key issue for NH3 synthesis and decomposition is the development of non-noble metal based, highly active and stable catalysts that can be operated under mild condition. With the understanding on the interaction of LiH and Li2NH with 3d metals or their nitrides, novel catalyst systems, i. e., LiH-3d transition metals for NH3 synthesis and Li2NH-3d transition metal for NH3 decomposition, that have activities surpassing the highly active Ru-based catalysts were developed. The unique chemistry among TM, Li, N and H creates a two-reactive center mediated pathway…


Influence of H2 / N2 Ratio on Dynamic Behavior of Ammonia Production on Ru Catalyst Under Low Pressure Condition

Recently deployment of renewable energy such as sunlight and wind power or deployment of process technologies for carbon dioxide capture and storage (CCS) is indispensable to reduce the CO2-emission. However, there are some issues to be solved in order to accelerate the mass deployment of renewable energy. Since amount of renewable energy quite changes unstably with time, which depends on weather and place, development of process systems technology is an issue for stable and effective utilization of electric power that is generated by fluctuating renewable energy. Those in national institute of National Institute of Advanced Industrial Science and Technology (AIST)…


Early Transition Metal Carbide and Nitride Supported Catalysts for Ammonia Synthesis

More than 180 million tons of NH3 are produced annual via the Haber-Bosch process which converts N2 and H2 at high temperatures (400 – 500°C) and pressures (150 – 300 bars). Ammonia synthesis also accounts for 1-2% of global energy consumption.1 The development of higher activity catalysts that can operate under less severe conditions would enhance the economics associated with and sustainability of NH3 synthesis. Research described in this paper investigates the performance of transition metal carbide and nitride supported metals for NH3 synthesis. Previously, Mo2C and Mo2N have been reported to be more active than Ru-based catalysts, but slightly…