Recent progress towards the electrosynthesis of ammonia from sustainable resources

Abstract

Ammonia (NH 3 ) is a key commodity chemical of vital importance for fertilizers. It is made on an industrial scale via the Haber Bosch process, which requires significant infrastructure to be in place such that ammonia is generally made in large, centralized facilities. If ammonia could be produced under less demanding conditions, then there would be the potential for smaller devices to be used to generate ammonia in a decentralized manner for local consumption. Electrochemistry has been proposed as an enabling technology for this purpose as it is relatively simple to scale electrolytic devices to meet almost any level of demand. Moreover, it is possible to envisage electrosynthetic cells where water could be oxidized to produce protons and electrons at the anode which could then be used to reduce and protonate nitrogen to give ammonia at the cathode. If this nitrogen were sourced from the air, then the only required infrastructure for this process would be supplies of water, air and electricity, the latter of which could be provided by renewables. Hence an electrosynthetic cell for ammonia production could allow NH 3 to be generated sustainably in small, low-cost devices requiring only minimal facilities. In this review, we describe recent progress towards such electrosynthetic ammonia production devices, summarizing also some of the seminal literature in the field. Comparison is made between the various different approaches that have been taken, and the key remaining challenges in the electrosynthesis of ammonia are highlighted.

Electrochemical Synthesis of Ammonia in Molten Salt Electrolyte Using Hydrogen and Nitrogen at Ambient Pressure

“…[23][24][25] A variety of factors need to be analyzed when selecting the cell material such as system operating temperature, current density, pressure, and conductivity which affect the ammonia production rate. It is important to note that conductivity of a solid electrolyte increases exponentially with temperature and by reducing cell thickness as reported by Giddey et al 26 Kyriakou et al 27 recently reported extensive literature data about low temperature, medium temperature and high temperature electrochemical NH 3 28 presented the recent developments in electrochemical NH 3 production and they categorized the sources of proton as water, hydrogen and sacrificial proton donors. They resulted that the techniques keeping the temperatures in the range of 100…”

Ammonia Synthesis Under Ambient Conditions: Selective Electroreduction of Dinitrogen to Ammonia on Black Phosphorus Nanosheets

“…under ambient conditions.D ensity functional theory calculations reveal that the active orbital and electrons of zigzag and diff-zigzag type edges of FL-BP NSs enable selective electrocatalysis of N 2 to NH 3 via an alternating hydrogenation pathway.T his work proves the feasibility of using an onmetallic simple substance as an itrogen-fixing catalyst and thus opening an ew avenue towardst he development of more efficient metal-free catalysts. [12][13][14][15] To this end, the search for an electrocatalytic NRR center in recent years has mainly focused on transition-metal-based materials. [1] At present, the energyintensive Haber-Bosch process is the main artificial synthesis route for ammonia, and this process uses more than 1% of global annual energy consumption and produces carbon dioxide emissions.…”

“…[12][13][14][15] To this end, the search for an electrocatalytic NRR center in recent years has mainly focused on transition-metal-based materials. [12][13][14][15] To this end, the search for an electrocatalytic NRR center in recent years has mainly focused on transition-metal-based materials.…”

Electrocatalytic Hydrogenation of N2to NH3by MnO: Experimental and Theoretical Investigations

“…[7,8] High temperature and pressure however is involved in the Haber-Bosch process for industrial-scale NH 3 production. [12,13] Although tackling the energy-and H 2 -intensive operations by the Haber-Bosch process, it is still challenged with N 2 activation and electrocatalysts for N 2 reduction reaction (NRR) are a prerequisite. In this context, a less energydemanding and environmentally benign alternative process for NH 3 production is highly desirable.…”

“…[12,13] Although tackling the energy-and H 2 -intensive operations by the Haber-Bosch process, it is still challenged with N 2 activation and electrocatalysts for N 2 reduction reaction (NRR) are a prerequisite. [12,13] Although tackling the energy-and H 2 -intensive operations by the Haber-Bosch process, it is still challenged with N 2 activation and electrocatalysts for N 2 reduction reaction (NRR) are a prerequisite.…”