Chemical looping of metal nitride catalysts: low-pressure ammonia synthesis for energy storage

Michalsky, Ronald; Avram, Alexandru M.; Peterson, Brian A.; Pfromm, Peter H.; Peterson, Andrew A.

doi:10.1039/c5sc00789e

Cited by 212 publications

(208 citation statements)

References 68 publications

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“…Therefore, TMNs have evolved a potential candidate for the noble metal material catalyst and consequently represented better activity i.e. for electrochemical ammonia synthesis [3][4][5] and solar thermochemical ammonia production [6][7][8] when compared with pure metals [9]. For catalytic nitrogen reduction to ammonia, these TMNs have the extra benefit over pure transition metals since nitrogen atoms are already incorporated in their structure.…”

Section: Introductionmentioning

confidence: 99%

Electrochemical synthesis of ammonia via Mars-van Krevelen mechanism on the (111) facets of group III–VII transition metal mononitrides

2017

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Section: Introductionmentioning

confidence: 99%

Electrochemical synthesis of ammonia via Mars-van Krevelen mechanism on the (111) facets of group III–VII transition metal mononitrides

2017

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“…24 In recent years, a strategy analogous to redox cycling for solar thermochemical water splitting 25 has emerged for the production of NH3 using solar energy to drive a thermochemical redox cycle where a metal oxide is reduced with hydrogen, carbon monoxide, or solid carbon in the presence of nitrogen to produce a metal nitride that is subsequently hydrolyzed by steam to reform the metal oxide and produce NH3. [26][27][28][29][30][31][32] For a cycle using AlN as the metal nitride redox material, 26 the reduction step is shown as reaction 1 and the desired hydrolysis of AlN step is shown as reaction 2:…”

Section: Introductionmentioning

confidence: 99%

Aluminum Nitride Hydrolysis Enabled by Hydroxyl-Mediated Surface Proton Hopping

Bartel

Muhich

Weimer

et al. 2016

ACS Appl. Mater. Interfaces

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Aluminum nitride (AlN) is used extensively in the semiconductor industry as a high-thermal-conductivity insulator, but its manufacture is encumbered by a tendency to degrade in the presence of water. The propensity for AlN to hydrolyze has led to its consideration as a redox material for solar thermochemical ammonia (NH3) synthesis applications where AlN would be intentionally hydrolyzed to produce NH3 and aluminum oxide (Al2O3), which could be subsequently reduced in nitrogen (N2) to reform AlN and reinitiate the NH3 synthesis cycle. No quantitative, atomistic mechanism by which AlN, and more generally, metal nitrides react with water to become oxidized and generate NH3 yet exists. In this work, we used density-functional theory (DFT) to examine the reaction mechanisms of the initial stages of AlN hydrolysis, which include: water adsorption, hydroxyl-mediated proton diffusion to form NH3, and NH3 desorption. We found activation barriers (Ea) for hydrolysis of 330 and 359 kJ/mol for the cases of minimal adsorbed water and additional adsorbed water, respectively, corroborating the high observed temperatures for the onset of steam AlN hydrolysis. We predict AlN hydrolysis to be kinetically limited by the dissociation of strong Al-N bonds required to accumulate protons on surface N atoms to form NH3. The hydrolysis mechanism we elucidate is enabled by the diffusion of protons across the AlN surface by a hydroxyl-mediated Grotthuss mechanism. A comparison between intrinsic (Ea = 331 kJ/mol) and mediated proton diffusion (Ea = 89 kJ/mol) shows that hydroxyl-mediated proton diffusion is the predominant mechanism in AlN hydrolysis. The large activation barrier for NH3 generation from AlN (Ea = 330 or 359 kJ/mol, depending on water coverage) suggests that in the design of materials for solar thermochemical ammonia synthesis, emphasis should be placed on metal nitrides with less covalent metal-nitrogen bonds and, thus, more-facile NH3 liberation.

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“…[25][26][27] At present, in the process research of N 2 reduction to NH 3 , there have been many kinds of synthesis processes explored under mild conditions, such as photochemical synthesis of NH 3 , [28,29] electrochemical synthesis of NH 3 , [30][31][32][33] photoelectrochemical synergistic synthesis of NH 3 , [34,35] plasma synthesis of NH 3 , [36][37][38] homogeneous and nitrogenase synthesis of NH 3 , [39][40][41] and cyclic synthesis of NH 3 . [42,43] However, photochemical technology is limited by the uncertainty of solar energy and a very low utilization rate. [44] The stability of nitrogenase is poor, and industrialization still has a long way to go.…”

Section: Introductionmentioning

confidence: 99%

“…[39] The recycling process is restricted by the complex process conditions and the consumption of a small amount of media. [42,43] Although the synthesis of NH 3 from N 2 and H 2 is thermodynamically exothermic (ΔH 298K = À 91.8 kJ · mol À 1 ), the large energy gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) in N 2 hinders the transfer of electrons to N 2 molecules, which makes N 2 reduction more difficult. [44] Compared with other processes, electrochemical transmission of electrons has obvious advantages, and its power source can be wind, water, solar energy, nuclear energy and other energy structures, which is more valuable in remote areas and easy to industrialize.…”

Section: Introductionmentioning

confidence: 99%

Synergistic Promotion of the Electrochemical Reduction of Nitrogen to Ammonia by Phosphorus and Potassium

Zhang

Liu

et al. 2019

ChemCatChem

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In the process of electrochemical ammonia synthesis using an aqueous solution as the electrolyte, most protons will preferentially compete for electrons for hydrogen generation. Herein, the carbon cloth loaded with Nano‐Fe was used as the cathode, and a K3PO4 solution was used as the electrolyte. The electrochemical reduction of N2 to NH3 was investigated. It was found that the K3PO4 electrolyte had an obvious promotion effect on the ammonia synthesis efficiency compared with other electrolytes. It was confirmed that phosphorus and potassium had a synergistic effect on the ammonia synthesis efficiency. K+ can effectively prevent H+ from adsorbing to the active site of a catalyst surface, thus inhibiting the formation of hydrogen. The solubility of the phosphate solution for N2 is better than that of other aqueous electrolyte solutions, thus effectively improving the ammonia production efficiency. The highest ammonia yield was 79.0±5×10−11 mol ⋅ s−1 ⋅ cm−2, and the faraday efficiency reached 16.68 %. These results provide an effective way to improve the conversion yield of electrochemical ammonia synthesis in water systems.

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Chemical looping of metal nitride catalysts: low-pressure ammonia synthesis for energy storage

Abstract: Design principles for reducible metal nitride catalysts are developed and demonstrated for ambient-pressure solar-driven N2 reduction into NH3.

Cited by 212 publications

References 68 publications

Electrochemical synthesis of ammonia via Mars-van Krevelen mechanism on the (111) facets of group III–VII transition metal mononitrides

Electrochemical synthesis of ammonia via Mars-van Krevelen mechanism on the (111) facets of group III–VII transition metal mononitrides

Aluminum Nitride Hydrolysis Enabled by Hydroxyl-Mediated Surface Proton Hopping

Synergistic Promotion of the Electrochemical Reduction of Nitrogen to Ammonia by Phosphorus and Potassium

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