How to Survive at Point Nemo? Fischer-Tropsch, Artificial Photosynthesis, and Plasma Catalysis for Sustainable Energy at Isolated Habitats

Abstract

Inhospitable, inaccessible, and extremely remote alike the famed pole of inaccessibility, aka Point Nemo, the isolated locations in deserts, at sea, or in outer space are difficult for humans to settle, let alone to thrive in. Yet, they present a unique set of opportunities for science, economy, and geopolitics that are difficult to ignore. One of the critical challenges for settlers is the stable supply of energy both to sustain a reasonable quality of life, as well as to take advantage of the local opportunities presented by the remote environment, e.g., abundance of a particular resource. The possible solutions to this challenge are heavily constrained by the difficulty and prohibitive cost of transportation to and from such a habitat (e.g., a lunar or Martian base). In this essay, the advantages and possible challenges of integrating Fischer-Tropsch, artificial photosynthesis, and plasma catalysis into a robust, scalable, and efficient self-contained system for energy harvesting, storage, and utilization are explored.

Keywords: Fischer–Tropsch; artificial photosynthesis; plasma catalysis.

Figure 1

Examples of “Points Nemo” on Earth and beyond? The actual Point Nemo, also known as “the oceanic pole of inaccessibility,” can be found at 48°52.6′S 123°23.6′W, and is regarded as the location most physically removed from any body of land (a). Indeed, one would need to cover at least a thousand miles of ocean in order to reach land, regardless of direction of travel. Other examples of similarly isolated poles and point of inaccessibility include the Eurasian pole of inaccessibility (EPIA) in the Gurbantünggüt Desert of China, which also happens to be the furthest point on land from the ocean; as well as the poles of accessibility for individual continents. While used metaphorically here to highlight remoteness and isolation, even less remote locations are difficult to settle. The logistics of providing sustained access to energy and input resources is one of the critical factors in determining the success of such settlements. The issue of transport becomes one of feasibility when extra‐terrestrial locations, e.g., on Moon and Mars are considered due, especially for heavy traditional systems. Reproduced under the terms of the CC BY‐SA 4.0 license.^{[ 4 ]} (b) Artist's impression of a Mars settlement, reprintred under terms of the CC BY license.^{[ 5 ]}

Figure 2

The basics of the Fischer–Tropsch technology, where carbon‐rich feedstock (gas, coal, or biomass) is first converted into a mixture of hydrogen and carbon monoxide called Syngas, and then processed in the presence of a catalyst into liquid fuels made of hydrocarbon chains.^{[ 17} , ^{18 ]} The Fischer–Tropsch process is a key stage in the whole technological chain of converting carbon‐containing substances into hydrocarbon fuels, where latter can be considered as mass‐ and cost‐efficient energy storage media—much more efficient than electric batteries. The technological chain of reactions is shown in the diagram. Water and CO₂ splitting using, e.g., an artificial photosynthesis‐based system and plasma are other important elements of the proposed energy system.

Figure 3

Identifying synergies for greater efficiency. Synergistic uses of (top) solar and electrical energy for CO₂ decomposition, and (bottom) plasma and chemistry in plasma‐enabled Fischer–Tropsch and Boudouard reactions. TOP PANEL: Solar‐glidarc carbon dioxide conversion system. a) A gliding arc discharge initiated in CO₂ is exposed to collimated solar irradiation, with additional gases injected into the system to accelerate processes conducive to CO₂ breakdown. b) Optical photograph of the built reactor. Reproduced with permission.^{[ 44 ]} Copyright 2020, Elsevier. BOTTOM PANEL: Fischer–Tropsch and Boudouard reactions for CO₂ conversion and hydrocarbon synthesis. Boudouard reaction is capable of producing the solid carbonous deposits out of carbon‐containing gas. c) Photo of an experimental facility used to conduct Boudouard reaction guided by a thermal plasma, where the gas mixture is introduced near the anode of the plasma‐generating circuit in a drift section. Reproduced with permission.^{[ 46 ]} Copyright 2019, Elsevier. d,e) Schematic diagram and optical photograph of the dielectric barrier discharge reactor. Reproduced with permission.^{[ 48 ]} Copyright 2019, Elsevier.

Figure 4

The availability of water is among key challenges in remote habitats, since virtually any sub‐system requires water for its reliable, efficient operation. This example illustrates the impact of water cooling on efficiency of CO₂ splitting. Carbon dioxide was split in a wire‐cylinder DBD plasma setup with autogenous cooling at standard ambient temperature and pressure. The production rate reached 26.1% without changing the discharge conditions with respect to the catalyst, atmosphere, or setup configuration. Additional removal of heat via, e.g., externally reticulated water further increased efficiency and stabilized and homogenized the plasma discharge. Reactor with a conventional wire‐cylinder DBD plasma contained in Pyrex glass is denoted as “A,” while the self‐cooling DBD facility is denoted as ‘B.’ Reprinted with permission.^{[ 45 ]} Copyright 2017, Wiley.

Figure 5

Artificial photosynthesis—one of the cornerstones of the proposed architecture for highly efficient, self‐sustained energy systems for remote habitats and extra‐terrestrial outposts. TOP PANEL: Photocatalytic water splitting by use of an assembly of nanowires made of metal nitride in neutral pH liquid media. a) A schematic to illustrate the best conditions for adsorption of solar radiation by use of the multi‐band InGaN assembly with different indium content. b) A design of the quadruple‐band InGaN nanowire, where an electric field is generated by a Mg lateral gradient doping, which is created by the Mg effusion cell tilted with respect to the nanowire; c) the field is engaged for separation of charges and their use for water redox reactions. Reproduced with permission.^{[ 84 ]} Copyright 2019, The Royal Society of Chemistry. BOTTOM PANEL: Photochemical diode artificial photosynthesis system for unassisted water splitting. d) The process of water splitting by use of double‐band nanowires with hydrogen evolution reaction catalyst dots arranged on their surfaces. Recombination or transfer of carriers is not employed in this method, as well as current matching along the non‐homogeneous vertical structure, which is in contrast to processes occurring in tandem photoelectrochemical cells or photovoltaic devices. Reactions on the side surfaces of every layer include oxidation of water and reduction of proton. e) A schematic of energy levels of the developed photochemical diode with a radial thickness d, where the built‐in electric field separates the electrons and holes and guides them toward the cathode and anode. Unlike the common p‐n photochemical diodes, just single photon is necessary to create an electron–hole pair to promote the redox reaction. Reproduced under the terms of the CC BY license.^{[ 85 ]}

Figure 6

Concept of vertically integrated Sun‐enabled power system. a) The proposed self‐contained system, dreamed for remote habitats including Moon and Mars settlements. The initial energy is supplied form the Sun and then distributed to the immediate customers and the plasma‐activated processes to produce CO, hydrogen and oxygen which is vitally required the Moon and Mars settlements for breathing and other purposes, apart from the energy production. The Fischer–Tropsch process is the used to produce liquid fuels that are very efficient energy storage media. Importantly, the system includes the production of solar cells for direct supply of solar electricity to the customers and accumulation system in the main energy generation unit. b) The first experiments on the production of solar cells out of the material similar to lunar regolith is shown in (b): an optical photograph of the semi‐finished monograin layer solar cell to be produced on the Moon. Reproduced with permission from Kristman et al. 2022.^{[ 97 ]} The efficient plasma‐catalysed water and carbon dioxide splitting systems, producing syngas and then liquid fuel via the FTP are the core of the energy conversion sub‐system. Next, liquid fuel is the mass‐efficient energy storage system.

Figure 7

Further steps—complex, hierarchical metamaterials for water splitting, photosynthesis and other processes and reactions related to the advanced energy systems. a) A complex metamaterial comprising hydrogenated TiO₂ nanorods decorated with carbon quantum dots for the efficient photoelectrochemical water splitting. Illustration of enhanced photochemical process in carbon quantum dots (CQDs)‐H/TiO₂ photoanodes. The hydrogenation reaction results in the generation of oxygen vacancies and Ti³⁺ cations in TiO₂ photoanodes to hinder the recombination of charge carriers; the quantum dots greatly intensify the process of harvesting of solar radiation. The developed photoanodes show the efficiency of ≈66.8% for the incident photon to current conversion, thus achieving almost sixfold increase with respect to the performance of pristine TiO₂. Reprinted with permission.^{[ 54 ]} Copyright 2019, American Chemical Society. b) Photocatalytic mechanism of three‐dimensional porous Z‐scheme silver/silver bromide/graphitic carbon nitride@nitrogen‐doped graphene aerogel. This complex material demonstrates excellent visible‐light photocatalytic and antibacterial activities. Reprinted with permission.^{[ 117 ]} Copyright 2019, Elsevier. To enhance the efficiency of water splitting photocatalysts, the recombination of exitons should bve suppressed by separation of holes and electrons via (c) random loading of co‐catalysts; (d) formation of facets; (e) with one‐dimensional nanostructures. Reprinted under the terms of the CC BY license.^{[ 118 ]} Copyright 2022, The Authors. f) Schematic of water molecules adsorption inside the GO flakes in the graphene oxide‐based paper featuring high water adsorption capacity. Graphene oxide paper used for packaging of fruits increased post‐harvest lifespan of produce by improving moisture adsorption and mitigating mold growth, suggesting future uses of this material in moisture management and in food safety context. Reprinted under the terms of the CC NY license.^{[ 119 ]} Copyright 2022, The Authors.

Figure 8

TOP PANEL: Further steps—novel materials for catalytic systems. a) Optical photographs of the open‐cell aluminium foams. b) Dependence of catalyst temperature on time for the packed foam and packed bed reactors. Reprinted with permission under the terms of the CC BY‐NC‐ND license.^{[ 126 ]} BOTTOM PANEL: Examples of cobalt crystal structures used for the FT process. Reprinted with permission^{[ 128 ]}

Figure 9

Effect of cobalt nanoparticle size in FT process. a) The relationship between the size of cobalt nanoparticle and turnover frequency. Data from van de Loosdrecht et al.,^{[ 130 ]} van Helden et al.,^{[ 131 ]} and elsewhere.^{[ 132} , ¹³³ , ¹³⁴ , ¹³⁵ , ¹³⁶ , ¹³⁷ , ^{138 ]} b) Multiple distinct Bn sites present on a single cobalt nanoparticle (face‐centred‐cubic structure, particle size: 4 nm). Note two types of reactive B5 sites. Reproduced with permission.^{[ 131 ]} Reproduced with permission.^{[ 128 ]}

Figure 10

a) Linear plot of the distribution of products generated using the FT synthesis, where vertical axis is the ln of the mole fraction and horizonal axis is carbon number. An assumption is made of carbon chain lengths being dependent only on the molar rates of chain propagation and termination. Fe, Ru, and Co are used as catalysts. Reproduced under the terms of the CC BY license.^{[ 124 ]} b) Hydrocarbon product distribution. Reproduced with permission.^{[ 128 ]}