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Innovation (Camb)
Innovation (Camb)
The Innovation
2666-6758
Elsevier

S2666-6758(24)00128-0
10.1016/j.xinn.2024.100690
100690
Article
Massive water production from lunar ilmenite through reaction with endogenous hydrogen
Chen Xiao 129
Yang Shiyu 129
Chen Guoxin 39
Xu Wei 19
Song Lijian 1
Li Ao 1
Yin Hangboce 1
Xia Weixing 1
Gao Meng 1
Li Ming 3
Wu Haichen 3
Cui Junfeng 3
Zhang Lei 3
Miao Lijing 3
Shui Xiaoxue 3
Xie Weiping 3
Ke Peiling 3
Huang Yongjiang 4
Sun Jianfei 4
Yao Bingnan 1
Ji Min 1
Xiang Mingliang 1
Zhang Yan 12
Zhao Shaofan 5
Yao Wei 5
Zou Zhigang 56
Yang Mengfei 5
Wang Weihua 2578
Huo Juntao huojuntao@nimte.ac.cn
12∗
Wang Jun-Qiang jqwang@nimte.ac.cn
12∗∗
Bai Haiyang hybai@iphy.ac.cn
257∗∗∗
1 Key Laboratory of Magnetic Materials and Devices, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201, China
2 Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China
3 Center of Test and Analysis, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201, China
4 School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, China
5 Qian Xuesen Laboratory of Space Technology, China Academy of Space Technology (CAST), Beijing 100049, China
6 College of Engineering and Applied Science, Nanjing University, Nanjing 210093, China
7 Institute of Physics, Chinese Academy of Sciences, Beijing 100049, China
8 Songshan Lake Materials Laboratory, Dongguan 523830, China
∗ Corresponding author huojuntao@nimte.ac.cn
∗∗ Corresponding author jqwang@nimte.ac.cn
∗∗∗ Corresponding author hybai@iphy.ac.cn
9 These authors contributed equally

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© 2024 The Author(s)
2024
https://creativecommons.org/licenses/by-nc-nd/4.0/ This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Finding water resources is a crucial objective of lunar missions. However, both hydroxyl (OH) and natural water (H2O) have been reported to be scarce on the Moon. We propose a potential method for obtaining water on the Moon through H2O formation via endogenous reactions in lunar regolith (LR), specifically through the reaction FeO/Fe2O3 + H → Fe + H2O. This process is demonstrated using LR samples brought back by the Chang’E-5 mission. FeO and Fe2O3 are lunar minerals containing Fe oxides. Hydrogen (H) retained in lunar minerals from the solar wind can be used to produce water. The results of this study reveal that 51–76 mg of H2O can be generated from 1 g of LR after melting at temperatures above 1,200 K. This amount is ∼10,000 times the naturally occurring OH and H2O on the Moon. Among the five primary minerals in LR returned by the Chang’E-5 mission, FeTiO3 ilmenite contains the highest amount of H, owing to its unique lattice structure with sub-nanometer tunnels. For the first time, in situ heating experiments using a transmission electron microscope reveal the concurrent formation of Fe crystals and H2O bubbles. Electron irradiation promotes the endogenous redox reaction, which is helpful for understanding the distribution of OH on the Moon. Our findings suggest that the hydrogen retained in LR is a significant resource for obtaining H2O on the Moon, which is helpful for establishing a scientific research station on the Moon.

Graphical abstract

Public summary

• The hydrogen retained in lunar minerals is a substantial material for producing water on the Moon.

• More than 50 kg of water can be produced from 1 ton of lunar regolith after melting at temperatures above 1,200 K.

• Ilmenite contains the most hydrogen among the five primary lunar minerals.

• Concurrent formation of iron (Fe) crystals and H2O bubbles is observed for the first time in in situ heating experiments.

• Electron irradiation can enhance the endogenous redox reaction between H and lunar regolith.

Published Online: August 22, 2024
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pmcIntroduction

Water (H2O) on the lunar surface is of significant interest owing to its crucial role in human survival. Infrared reflectance spectra from missions such as Cassini, Deep Impact, and Chandrayaan-11,2,3,4 have revealed the widespread presence of H2O, predominantly as hydroxyl (OH). These near-infrared spectra have facilitated detailed analyses of the lunar water’s latitude3,5 and diurnal dependencies,5,6 as well as the compositional characteristics of the water. Evaluations of lunar regolith (LR) samples have confirmed the presence of H2O within agglutinitic glass,7 volcanic glass,8 and plagioclase.9 However, these sources of H2O are limited to concentrations ranging from 10 to 1,000 ppm, thus highlighting the need to identify more abundant lunar H2O reservoirs.

The presence of solar-wind-implanted hydrogen (H) on the Moon has led to the hypothesis that redox reactions between H and oxide minerals might produce H2O. The Chang’E-5 (CE-5) mission, in contrast to its predecessors, Apollo and Luna, targeted a high-latitude landing site in the northeastern Oceanus Procellarum basin (43.06°N, 51.92°W),10 which is known for its elevated H concentration.3,5,11 However, recent analyses12,13,14,15 suggest that the CE-5 LR samples are exceptionally dry, with an H2O content of only 283 ppm.16 This low H2O content observed in the CE-5 samples is attributable to their relatively younger age compared with samples from the Apollo and Luna missions.17 Consequently, there has been less reaction between H and lunar oxides.18,19 Additionally, the characteristics of LR particles affect the retention of H from solar proton implantation.7,20,21,22,23,24,25,26 The regolith returned by the CE-5 mission presents a unique opportunity to further investigate lunar H and H2O resources.27,28 Studying the potential production of H2O from redox reactions between implanted H and oxides, as well as identifying minerals with higher H content, is of considerable value.

In this study, we investigated the H content in various lunar minerals and the production of H2O from CE-5 LR at high temperatures through a range of advanced material characterization techniques. The reactions were characterized through several methods, including transmission electron microscopy (TEM), Lorentz TEM, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), electron energy loss spectroscopy (EELS), X-ray photoelectron spectroscopy (XPS), thermal gravimetric analysis (TGA), vibrating-sample magnetometry, and flash differential scanning calorimetry (DSC). Advanced spherical aberration-corrected TEM, coupled with high EELS, was used to elucidate the evolution of microstructures in lunar particles and the H content. The microstructure, chemical composition, and endogenous reactions of primary lunar minerals, including FeTiO3 ilmenite, olivine, pyroxene, plagioclase, and glass, were examined in detail. This work provides pioneering insights into water production on the Moon through the reaction between H and lunar minerals.

Results and discussion

The CE-5 LR is heated above its melting temperature, and its physical properties are studied. Figure 1A shows the XPS of the valence states of iron (Fe) during the heating process. Figure 1B illustrates the concentration of Fe in different valence states—Fe(0), Fe2+, and Fe3+—across a temperature range from room temperature to 1,373 K. Notably, up to 873 K, the Fe(0) content remains largely unchanged, while some Fe3+ ions are reduced to Fe2+ at around 773 K. At 1,323 K, where the LR melts, ∼68.1% of the Fe is reduced to Fe(0), while the contents of Fe2+ and Fe3+ decrease to 23.2% and 8.7%, respectively. The increase in Fe(0) is attributed to reduction by H, a reaction facilitated by enhanced diffusion in the molten state of the LR.Figure 1 Formation of Fe crystals and water via the heating of lunar regolith

(A) XPS spectra of Fe 2p for LR annealed from room temperature to 1,373 K (melting point).

(B) Evolution of Fe(0), Fe2+, and Fe3+ concentrations derived from (A) as a function of temperature. The orange dashed line indicates that electron irradiation promotes Fe reduction at a lower temperature of ∼473 K.

(C) Magnetization (Ms) of LR samples annealed at various temperatures (in K).

(D) Weight change of LR during heating.

(E) SEM image of molten LR showing Fe dendrites embedded in a glassy matrix.

(F) EDS mappings of elements for the area highlighted by the purple dashed square in (E).

(G) SEM image and corresponding EBSD micrographs of molten LR. In the EBSD image, the colorful regions represent Fe crystals in different orientations, while the dark gray areas denote the glassy matrix.

(H) Defocused TEM image of a Fe crystal embedded in the glassy matrix.

(I) High-resolution TEM image of the Fe-glass interface.

The amount of Fe(0) is estimated based on magnetic properties. Following the formation of Fe(0), the magnetic moment (Ms) considerably increases from 0.9 to 34.22 emu g−1. For pure Fe, the Ms is ∼217 emu g−1.29 Therefore, the content of Fe(0) in molten LR is ∼157 mg g−1. According to the reactions shown in Equations 1 and 2, 1 g of molten LR can generate 51–76 mg of H2O with 5.62–8.43 mg of H involved in the reaction.(Equation 1) FeO+2H→Fe(0)+H2O

(Equation 2) Fe2O3+6H→2Fe(0)+3H2O

Once the LR melts, the gaseous H2O can evaporate. At 1,523 K, the weight decreases by ∼6.7 wt.% (Figure 1D), which is consistent with the H2O content estimated from the magnetization data.

After the CE-5 LR is cooled to room temperature, the molten lunar LR transforms into a composite of Fe dendrites embedded in a glassy matrix (Figures 1E–1I). The SEM image in Figure 1E provides a detailed view of the surface of the LR after the melt has been quenched. Elemental mappings shown in Figure 1F confirm the presence of Fe dendrites, while other elements are distributed homogeneously throughout the matrix. The lattice orientation of the Fe dendrites is examined through electron backscatter diffraction (EBSD; Figure 1G). The EBSD color differentiation highlights the distinct orientations of Fe crystals, with darker areas representing the glassy nature of the matrix. The Lorentz TEM image displays clear magnetic domain walls (Figure 1H), which confirms the ferromagnetism of the Fe dendrites. The high-resolution TEM (HRTEM) image (Figure 1I) reveals the periodic atomic structure of the Fe crystals and the disordered atomic structure of the glassy matrix. These observations are further supported by the selected-area electron diffraction patterns shown in the insets of Figure 1I.

The H content in various lunar minerals is studied. According to previous works,30,31 the CE-5 LR consists of ∼44.5 wt.% pyroxene, 30.4 wt.% plagioclase, 15.5 wt.% glasses, 6.0 wt.% ilmenite, and 3.6 wt.% olivine. As shown in Figure 2A, the peak at 12.5 eV corresponds to the H signal.32 The integrated area for the EELS peak of H, shown in Figure 2B, represents the concentration of H in various lunar minerals. Among these minerals, FeTiO3 ilmenite has the highest H concentration, approximately four times that of plagioclase and over 10 times that of glassy particles. The H concentrations of pyroxene and olivine are negligible compared with those of the other minerals. Considering the abundance of these minerals in LR, a weighted H content is illustrated in the inset of Figure 2B. Despite constituting only 6.0% of the LR, ilmenite retains ∼38.3% of the total H content, while plagioclase, which makes up 30.4 wt.% of the regolith, accounts for 47.6% of the total H content.Figure 2 Hydrogen content in lunar minerals

(A) EELS peak for hydrogen in different lunar minerals shows that ilmenite (IL) contains the highest hydrogen content.

(B) Concentration of hydrogen in different lunar minerals, obtained through the integration of the EELS peak area. The inset shows the weighted hydrogen content in lunar regolith, considering the percentage of each mineral in the overall regolith.

(C and D) Ideal atomic packing structure for FeTiO3 IL in projections of [001] and [4¯11] orientations.

(E and F) High-resolution TEM images for lunar IL in [001] and [4¯11] orientations; insets are selected-area electron diffraction patterns.

(G and H) Simulated atomic packing structure for lunar FeTiO3 with four injected solar H, which shows similar lattice content to real lunar FeTiO3.

The atomic packing structure of FeTiO3 ilmenite is examined through HRTEM. The standard lattice structures for FeTiO3 in the [001] and [4¯11] orientations are shown in Figures 2C and 2D, respectively. The HRTEM images for these orientations are presented in Figures 2E and 2F. The lattice spacing for lunar ilmenite is slightly larger than the standard lattice spacing. For example, in the [001] orientation, the lattice spacing increases by 3.0%, from 0.302 to 0.311 nm. In the [4¯11] orientation, it increases by 4.7%, from 0.276 to 0.289 nm. This expansion is attributable to the injection of H.33,34,35 To verify this hypothesis, the atomic packing structure of FeTiO3 doped with H is calculated using density functional theory (Figures 2G and 2H). When four H atoms are introduced into one FeTiO3 unit cell, the lattice constants for the [001] and [4¯11] orientations are ∼0.312 and ∼0.290 nm, respectively, consistent with the TEM results. Notably, most of the H atoms are adsorbed in the sub-nanometer tunnels in the [4¯11] orientation (Figures 2F and 2H). The magnetism and TGA results indicate that the total H content in LR is ∼0.56 wt.%. EELS data show that 38.3% of this H is captured by ilmenite. Considering that ilmenite constitutes 6.0 wt.% of the LR, the H content in the LR can be calculated as 0.56wt.%×38.3%6.0wt.% = 3.57 wt.%. The molar mass of FeTiO3 is ∼151.7 g/mol, which suggests that there are about 151.7 × 3.57% = 5.4 H atoms per FeTiO3 molecule. This result is consistent with the simulation findings.

Our subsequent investigations focus on the endogenous reaction between implanted H and ilmenite particles at elevated temperatures. Figure 3 displays TEM images of the nanostructures of an ilmenite particle heated to 1,173 K. Numerous nanocrystals (dark particles in Figures 3A and 3B) are uniformly distributed throughout the sample. Notably, all these nanocrystals are associated with a bubble (bright contrast in Figures 3A and 3B) nearby. STEM images (Figures 3C and 3D) further confirm this concurrent nanocrystal-bubble structure, with bright nanocrystals accompanied by dark bubbles. The zoomed-in nanocrystal-bubble structure is further detailed in Figures 3E–3H. EDS mapping (Figure 3I) confirms that these nanocrystals are composed of iron (Fe). Lorentz TEM images (Figure S8) reveal a vortex magnetic domain structure, which is characteristic of magnetic nanocrystals.36 Point-scanning EELS spectra (Figures 3J and 3K) taken at the bubbles show a peak around 8.5 eV, which indicates the presence of H2O,25,37 while the peak for H at 12.5 eV disappears.Figure 3 Precipitation of Fe nanocrystal-H2O bubble pairs in lunar IL

(A) TEM image of the IL sample annealed at 973 K.

(B) Zoomed-in image of the red dashed square in (A).

(C and D) Scanning TEM images corresponding to (A) and (B), respectively.

(E–H) Zoomed-in TEM and STEM images of Fe nanocrystal-H2O bubble pairs in cyan dashed squares within the cyan dashed squares in (B) and (D). Yellow dashed curves outline the borders of the H2O bubbles.

(I) EDS mapping of Fe in the blue dashed square in (C).

(J and K) STEM image and EELS spectra at different positions in the annealed IL sample in (J).

The concurrent formation of Fe nanocrystals and H2O bubbles in ilmenite provides evidence that H, implanted by the solar wind, is a significant resource for producing H2O. For example, the reaction FeO+2H→highTFe+H2O illustrates this process. Notably, this reaction is not observed in terrestrial FeTiO3 (Figure S10) because it lacks implanted H. However, after H is implanted into terrestrial FeTiO3, the redox reaction occurs (Figure S11). The concurrent formation of Fe nanocrystals and H2O bubbles is not observed in other LR minerals when heated up to 973 K (Figures S12–S15). Although H retained in plagioclase accounts for nearly 50% of the total H in lunar minerals, the formation of H2O bubbles is challenging owing to the low H concentration. Nevertheless, at high temperatures, H2O may aggregate and form bubbles that are subsequently released.

The effect of electron irradiation on H2O extraction is studied in situ using a Spectra 300 transmission electron microscope with a current density of 1.5–2 nA and an acceleration voltage of 300 kV (Figures 4A–4F). At 473 K, bubbles begin to nucleate and expand (Figures 4C–4E, dashed circles). By 773 K, numerous bubbles and dark Fe nanocrystals occur throughout the sample (Figure 4F). A broader perspective (Figure 4G) shows that bubbles form exclusively within the region irradiated by the electron beam, with the boundary outlined by a white dashed line. This effect is attributable to the enhanced atomic diffusivity under electron irradiation. A peak corresponding to H2O at 8.5 eV is detected in the EELS spectrum within the irradiated zone as shown in the site 1 spectrum in Figure 4I and the spectra in Figure 4K. Notably, the formation temperature of H2O with electron irradiation (473 K) is considerably lower than that in the absence of irradiation (∼873 K; Figures S16 and S17). Thus, electron irradiation effectively promotes H2O production (Figure 1B, orange curve).Figure 4 Electron irradiation promoting the reaction of H with IL

(A–F) In situ HRTEM images of the IL sample at different temperatures ranging from 293 to 773 K, obtained under strong electron irradiation. Yellow dashed circles in (C)–(E) highlight the forming bubbles. Arrows in (F) indicate the Fe nanocrystals.

(G) Zoomed-out TEM image after heating, with the electron irradiation-damaged area marked by a white dashed curve.

(H and I) EELS spectra from regions close to and outside the irradiated area, with corresponding points indicated on the TEM image.

(J and K) EELS spectra within the irradiated area, with corresponding points shown on the TEM image. Peaks at 8.5 and 12.5 eV correspond to H2O and H2, respectively.

According to the above analysis, we propose a strategy for on-site H2O extraction on the Moon (Figure 5). LR can be heated by concentrating sunlight using concave mirrors. Once the regolith melts, the H retained in the regolith will react with Fe oxides, producing large amounts of H2O and Fe. The H2O vapor is then collected under a cover and pumped into a water tank. This H2O can meet the needs of humans, animals, and plants. Additionally, the H2O can be electrochemically decomposed into O2 and H2. The O2 will support life, while the H2 can provide energy.Figure 5 Strategy for on-site H2O production on the Moon

Focused sunlight is used to melt lunar regolith, facilitating the reaction between solar wind-implanted H and Fe oxides to produce water. This water can be used to support life and can also be electrochemically decomposed into oxygen and hydrogen.

A previous study showed that helium atoms mainly formed bubbles and were distributed within the surface amorphous layer of ilmenite particles.38 In contrast, our observations suggest a more uniform distribution of H ions within ilmenite particles, which extends from the amorphous surface layer to the internal crystalline phases. This solid solution-like dispersion is attributed to the small size and reactive nature of H. Elevated temperatures enable substantial H to react with ilmenite, thus reducing Fe2+ to Fe(0) and producing H2O. This leads to the concurrent formation of Fe nanocrystals and H2O bubbles. Previous studies39,40,41,42 have suggested transporting H2 from Earth to the Moon to produce H2O through reactions with ilmenite. This work, however, demonstrates for the first time that H retained in LR, particularly in FeTiO3 ilmenite, can generate significant amounts of water through endogenous reactions, especially when the regolith is melted at high temperatures or subjected to electron irradiation.

Fe(0) formation cannot be attributed to the disproportionation of Fe2+ into Fe(0) and Fe3+, as no detectable presence of Fe(0) or Fe3+ is observed in annealed terrestrial ilmenite (Figures S19 and S20). The DSC traces (Figure S19) show neither endothermic nor exothermic reactions. Additionally, the atomic configuration of terrestrial ilmenite remains unchanged after heating to 1,473 K (Figure S20).

Before reaching its molten state, the precipitated Fe nanocrystals are less than 15 nm in diameter and exhibit superparamagnetic behavior. Upon melting, these Fe nanocrystals coalesce to form larger particles or dendrites, which exhibit strong ferromagnetic characteristics, as evidenced by the pronounced magnetization shown in Figure 1C. In contrast, parallel control experiments on terrestrial ilmenite do not reveal any significant change in magnetization (Figure S19). This observation further rules out the possibility of disproportionation reactions of Fe2+ in FeTiO3 into Fe(0) and Fe3+.

The abundant formation of encapsulated H2O bubbles indicates a significant resistance to the release of H2O gas. This makes it challenging to directly extract H2O from LR on site. Heating the LR above its melting point of ∼1,373 K can facilitate the merging of H2O bubbles within the molten matrix, thereby aiding in the release of H2O gas. Previous studies have confirmed that the H-rich LR should be at least 1 m thick.43,44,45 The total weight of these regolith deposits is ∼5.7 × 1013 tons, which can potentially produce around 3 × 1015 kg of water.

Our in situ TEM analyses, combined with intense electron irradiation, reveal an accelerated release of entrapped H in LR upon electron exposure. This finding enhances our understanding of the distribution patterns of lunar H2O and H, indicating that H2O/OH levels in low-altitude regolith are lower than those in high-altitude regolith.3,5 This discrepancy is attributable to the more intense solar wind irradiation at lower altitudes, where there are higher concentrations of electrons. Additionally, temperatures at lower altitudes are higher than those at higher altitudes. The combination of high temperatures and strong electron (solar wind) irradiation thus accelerates the release of H2O/H at lower altitudes on the Moon.

In summary, we observe that a substantial amount of H2O can be produced via melting CE-5 LR. Our estimates indicate that 1 g of LR could yield ∼51–76 mg of H2O, along with 157 mg of Fe(0). FeTiO3 ilmenite contains the highest H content among the lunar minerals studied. Further investigation of the physical properties of FeTiO3 ilmenite is needed to determine effective methods for separating it from other lunar minerals, which will be valuable for on-site operations on the Moon. Furthermore, our studies highlight the catalytic role of electron irradiation in promoting H release and facilitating H2O synthesis at lower temperatures. Although LR is relatively dry under ordinary conditions, it could become a significant H2O reservoir once heated to its melting point. These findings are not only of great interest to geochemistry but also offer valuable insights for future planetary research.

Materials and methods

Sample preparation

The CE-5 lunar samples (CE5C0400) used in this study were collected from the lunar surface and provided by the China National Space Administration. These samples were sealed in a container filled with high-purity argon and then transferred to a glove box with a continuous flow of high-purity argon (Mikrouna) at the Ningbo Institute of Materials Technology & Engineering, Chinese Academy of Sciences. The lunar particles, ranging in size from a few microns to tens of microns, were then placed onto sticky carbon tape. The selected particles were characterized through morphological observation and elemental mapping using a field emission scanning electron microscope (Verios G4 UC, Thermo Scientific) equipped with an EDS detector (X-Man series, Oxford). The measurement parameters were an acceleration voltage of 15.0 kV and a probe current of 3.2 nA. TEM specimens were prepared via the focused ion beam technique (Helios G4 CX, Thermo Scientific). Regions of interest on the selected particles were coated with a thick Pt film (∼1 μm) deposited by an ion beam to protect the particle surfaces from damage during ion milling. For specimen heating, the specimens were mounted on a specially designed chip sensor (Thermo Scientific).

Structure and element characterization

The crystal structures of these particles were characterized using a spherical aberration-corrected scanning transmission electron microscope (Spectra 300, equipped with a fifth-order aberration corrector, Thermo Scientific). Measurements were conducted at an acceleration voltage of 300 kV, and STEM images were acquired in high-angle annular dark field mode. To detect H, EELS was performed using a Gatan 1066 system with a collection semi-angle of 50 rad. The energy resolution, determined by the full width at half maximum of the zero-loss peak, was ∼0.3 eV. The elemental content obtained from EDS enabled the classification of lunar particles (Table S1; Figure S1). EDS mapping was conducted using an EDS detector (Thermo Scientific) equipped with four probes. To investigate the effect of electron irradiation, additional TEM was performed using a Talos F200X (Thermo Scientific) operating at an acceleration voltage of 200 kV. Molten LR samples were polished via the broad ion beam technique46 (TIC 3X series, Leica) at 7 kV for 10 h to prepare them for EBSD. In the EBSD experiments (Symmetry series, Oxford), an accelerating voltage of 20 kV, a working distance of 13 mm, and a step size of 50 nm were used to obtain orientation maps. The valence states of iron in LR were analyzed via XPS (XPS 6I60, Bruker).

Simulation of atomic packing structure of lunar ilmenite

The Vienna ab initio simulation package was used to investigate the effects of doping FeTiO3 with H atoms at various ratios, with particular emphasis on the resulting lattice distortions. H atoms were strategically positioned in the largest available interstitial spaces to maintain structural stability. The conjugate gradient algorithm was employed to relax the system. The iterative process for electronic steps was considered complete once the variation in the total energy of the system between successive electronic steps fell below 10−6 eV. Conversely, the iteration for ionic steps was terminated after 200 steps. The structural optimization process took into account the antiferromagnetic characteristics of the system. For all computational processes, electron interactions were described using the Perdew-Burke-Ernzerhof functional, a refinement of the generalized gradient approximation for exchange-correlation potential. Owing to the sufficiently large size of the supercell, only the gamma point was considered in the Brillouin zone.

Magnetic property measurement

The magnetic domain structure of the heated LR sample was observed using a Lorentz transmission electron microscope with a customized JEM-2100F.47 The magnetic properties of LR annealed at different temperatures were measured using a magnetic property measurement system (Quantum Design, measurement precision: <1 × 10−8 emu at H = 0 T; <8 × 10−8 emu at H = 7 T).

Thermal property measurement

Thermal analysis of terrestrial ilmenite was conducted using a differential scanning calorimeter (404F1, Netzsch). The weight loss of LR during the heating process was measured with a simultaneous thermal analyzer (TG-DSC, STA 449F3, Netzsch).

Acknowledgments

We thank all the staff of the Chang’E Lunar Exploration Project for their work in returning lunar samples and the China National Space Administration (CNSA) for providing the lunar sample. Discussions with Prof. Fang Fang about hydrogen storage in materials is acknowledged. Financial support from the 10.13039/501100012166 National Key R&D Program of China (2018YFA0703600 ), the 10.13039/501100001809 National Natural Science Foundation of China (NSFC 52222105 , 51922102 , 92163108 , 61888102 , and 51827801 ), the 10.13039/501100004739 Youth Innovation Promotion Association CAS (2019296 ), the 10.13039/501100004731 Zhejiang Provincial Natural Science Foundation of China (LZ22A030001 and LR22E010004 ), and the Ningbo 2025 Science and Technology Innovation Project is acknowledged.

Author contributions

W.H.W., H.Y.B., M.F.Y., and Z.G.Z. led this project. J.Q.W. and J.T.H. conceived and guided the research. X.C., W.X., J.Q.W., and J.T.H. designed the experiments. X.C., L.J.S., M.G., and L.Z. prepared the samples. X.C., G.X.C., W.X.X., M.L., H.C.W., J.F.C., and P.L.K. conducted the TEM and EELS measurements. S.Y.Y. did the simulation work. X.C. and L.J.M. did the XPS analysis. X.C., J.-Q.W., X.X.S., W.P.X. and P.L.K. did the thermal analysis. Y.J.H. and J.F.S. did the proton irradiation experiments. All authors discussed the results and contributed to the preparation of the manuscript. J.Q.W., X.C., J.T.H., H.Y.B. and W.H.W. wrote the manuscript.

Declaration of interests

The authors declare no competing interests.

Lead contact website

https://non-crystal.nimte.ac.cn/

Supplemental information

Document S1. Figures S1–S20 and Table S1

Document S2. Article plus supplemental information

It can be found online at https://doi.org/10.1016/j.xinn.2024.100690.
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