The Feasibility of Electrochemical Ammonia Synthesis in Molten LiCl–KCl Eutectics

Nanocarbon for Energy Material Applications: N2 Reduction Reaction

Nanocarbons are an important class of energy materials and one relevant application is for the nitrogen reduction reaction, i.e., the direct synthesis of NH₃ from N₂ and H₂ O via photo- and electrocatalytic approaches. Ammonia is also a valuable energy or hydrogen vector. This perspective paper analyses developments in the field, limiting discussion to nanocarbon-based electrodes. These aspects are discussed: i) active sites related to charge density differences on C atoms associated to defects/strains, ii) doping with heteroatoms, iii) introduction of isolated metal ions, iv) creation and in situ dynamics of metal oxide(hydroxide)/nanocarbon boundaries, and v) nanocarbon characteristics to control the interface. Discussion is focused on the performances and mechanistic aspects. Aim is not a systematic state-of-the-art report but to highlight the need to use a different perspective in studying this challenging reaction by using selected papers. Notwithstanding the large differences in the proposed nature of the active sites, fall all within a restricted range of performances, far from the targets. A holistic approach is emphasized to make a breakthrough advance.

Emerging Materials and Methods toward Ammonia-Based Energy Storage and Conversion

Efficient storage and conversion of renewable energies is of critical importance to the sustainable growth of human society. With its distinguishing features of high hydrogen content, high energy density, facile storage/transportation, and zero-carbon emission, ammonia has been recently considered as a promising energy carrier for long-term and large-scale energy storage. Under this scenario, the synthesis, storage, and utilization of ammonia are key components for the implementation of ammonia-mediated energy system. Being different from fossil fuels, renewable energies normally have intermittent and variable nature, and thus pose demands on the improvement of existing technologies and simultaneously the development of alternative methods and materials for ammonia synthesis and storage. The energy release from ammonia in an efficient manner, on the other hand, is vital to achieve a sustainable energy supply and complete the nitrogen circle. Herein, recent advances in the thermal-, electro-, plasma-, and photocatalytic ammonia synthesis, ammonia storage or separation, ammonia thermal/electrochemical decomposition and conversion are summarized with the emphasis on the latest developments of new methods and materials (catalysts, electrodes, and sorbents) for these processes. The challenges and potential solutions are discussed.

Lithium-based Loop for Ambient-Pressure Ammonia Synthesis in a Liquid Alloy-Salt Catalytic System

The Haber-Bosch process for ammonia (NH₃ ) production in industry relies on high temperature and high pressure and is therefore highly energy intensive. In addition, the activity of the solid transition metal-based catalysts used is typically limited by the scaling relation between activation barrier for N₂ dissociation and nitrogen-binding energy. Here, an innovative Li-based loop in a liquid alloy-salt catalytic system for ambient-pressure NH₃ synthesis from N₂ and H₂ was developed. The looping process consisted of three reaction steps taking place simultaneously. The first step was the nitrogen fixation by Li in the liquid Li-Sn alloy to form lithium nitride (Li₃ N), which floated up and dissolved into the molten salt. The second step was the hydrogenation of the Li₃ N to produce NH₃ and lithium hydride (LiH) in the molten salt. The third step was the decomposition of the LiH to regenerate Li in the presence of Sn. An average NH₃ yield rate of 0.025 μg s^-1 was achieved in an 81 h test at 510 °C and ambient pressure. The floating and dissolution of Li₃ N realized in the liquid catalytic system enabled circumventing the scaling relation exerted on Li, and the remarkable properties of liquid alloy and molten salt offered extraordinary advantages for NH₃ synthesis at ambient pressure.

Eutectics: formation, properties, and applications

Various eutectic systems have been proposed and studied over the past few decades. Most of the studies have focused on three typical types of eutectics: eutectic metals, eutectic salts, and deep eutectic solvents. On the one hand, they are all eutectic systems, and their eutectic principle is the same. On the other hand, they are representative of metals, inorganic salts, and organic substances, respectively. They have applications in almost all fields related to chemistry. Their different but overlapping applications stem from their very different properties. In addition, the proposal of new eutectic systems has greatly boosted the development of cross-field research involving chemistry, materials, engineering, and energy. The goal of this review is to provide a comprehensive overview of these typical eutectics and describe task-specific strategies to address growing demands.

The Position of Ammonia in Decarbonising Maritime Industry: An Overview and Perspectives: Part I : Technological advantages and the momentum towards ammonia-propelled shipping

Shipping, which accounts for 2.6% of global carbon dioxide emissions, is urged to find clean energy solutions to decarbonise the industry and achieve the International Maritime Organization (IMO)’s greenhouse gas (GHG) emission targets by 2050. It is generally believed that hydrogen will play a vital role in enabling the use of renewable energy sources. However, issues related with hydrogen storage and distribution currently obstruct its implementation. Alternatively, an energy-carrier such as ammonia with its carbon neutral chemical formula, high energy density and established production, transportation and storage infrastructure could provide a practical short-term next generation power solution for maritime industry. This paper presents an overview of the state-of-the-art and emerging technologies for decarbonising shipping using ammonia as a fuel, covering general properties of ammonia, the current production technologies with an emphasis on green synthesis methods, onboard storage and ways to generate power from it.

Review of Recent Progress in Green Ammonia Synthesis

Most of the global production of ammonia requires fossil fuels and is associated with considerable greenhouse gas emissions. Replacing fossil fuel ammonia with green or zero-carbon ammonia is a major focus for academia, industry and governments. Ammonia is a key component in fertiliser but is also attracting increasing interest as a carbon-free fuel for the maritime sector and as a hydrogen vector. This report describes the use of green (electrolysed) hydrogen in conventional Haber Bosch plants and predicts adoption of the technology by 2030. Further into the future, direct green ammonia synthesis by electrocatalytic and photocatalytic means may present a cost-effective alternative to the Haber Bosch process. Electrocatalytic and photocatalytic routes to ammonia are reviewed, the catalytic systems are compared and their potential for meeting the likely demand and cost for ammonia considered.