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DOE OSTI · 2998278

Chemical Control of Symmetry and Bandgap in Tungsten Oxyhalide van der Waals Semiconductors

Cox, Jordan [Columbia Univ., New York, NY (United States)] (ORCID:0000000342660990)·Mihalyi-Koch, Willa [Columbia Univ., New York, NY (United States)] (ORCID:0000000329847611)·Beck, Sophie [Flatiron Institute, New York, NY (United States); Technische Univ. Wien (Austria)]·Seewald, Eric [Columbia Univ., New York, NY (United States)]·Kundu, Asish K. [Brookhaven National Laboratory (BNL), Upton, NY (United States). National Synchrotron Light Source II (NSLS-II)] (ORCID:0000000321991053)·Cui, Zhi-Hao [Columbia Univ., New York, NY (United States)] (ORCID:0000000273894063)·Schertenleib, Till [Columbia Univ., New York, NY (United States); Ecole Polytechnique Federale Lausanne (EPFL) (Switzerland)] (ORCID:0000000349895821)·Huang, Chun-Ying [Columbia Univ., New York, NY (United States)]·Shao, Yinming [Columbia Univ., New York, NY (United States); Pennsylvania State Univ., University Park, PA (United States)]·Qiu, Siyuan [Columbia Univ., New York, NY (United States)]·Trovatello, Chiara [Columbia Univ., New York, NY (United States)] (ORCID:0000000281509743)·Chica, Daniel G. [Columbia Univ., New York, NY (United States)]·Huang, Xiong [Columbia Univ., New York, NY (United States)] (ORCID:0000000320358387)·Song, Xiaoyu [Columbia Univ., New York, NY (United States)] (ORCID:0000000333840527)·Koch Liston, André [Columbia Univ., New York, NY (United States)]·Ziebel, Michael E. [Columbia Univ., New York, NY (United States)] (ORCID:0000000318578292)·Vescovo, Elio [Brookhaven National Laboratory (BNL), Upton, NY (United States). National Synchrotron Light Source II (NSLS-II)]·Delor, Milan [Columbia Univ., New York, NY (United States)] (ORCID:0000000294809235)·Schuck, P. James [Columbia Univ., New York, NY (United States)]·Reichman, David R. [Columbia Univ., New York, NY (United States)] (ORCID:0000000252655637)·Zhu, Xiaoyang [Columbia Univ., New York, NY (United States)]·Billinge, S. J. L. [Columbia Univ., New York, NY (United States)] (ORCID:0000000297344998)·Basov, Dmitri N. [Columbia Univ., New York, NY (United States)]·Pasupathy, Abhay N. [Columbia Univ., New York, NY (United States); Brookhaven National Laboratory (BNL), Upton, NY (United States)] (ORCID:0000000227440634)·Roy, Xavier [Columbia Univ., New York, NY (United States)] (ORCID:0000000288500725)
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Abstract

Tunability in solid-state materials is essential for testing theory, discovering quantum phases, and enabling functionality. Layered van der Waals (vdW) semiconductors offer a unique platform, providing new degrees of freedom at the two-dimensional (2D) limit through exfoliation and external controls. Here, in this study, we demonstrate tunability of symmetry and electronic structure via halogen substitution in a family of layered vdW tungsten oxyhalides. Substituting the halogens in WO 2 X 2 (X = I, Br, Cl) tunes the bandgap across a broad energy range and modifies the structural symmetry from centrosymmetric to noncentrosymmetric. By alloying WO 2 I 2– y Br y , we continuously tune the polar distortion and optical gap across the visible range. These insights into halogen substitution effects on symmetry and electronic structure lay the foundation for new tunable vdW semiconductors for optoelectronics and nonlinear optics.

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Cox, Jordan [Columbia Univ., New York, NY (United States)] (ORCID:0000000342660990), Mihalyi-Koch, Willa [Columbia Univ., New York, NY (United States)] (ORCID:0000000329847611), Beck, Sophie [Flatiron Institute, New York, NY (United States); Technische Univ. Wien (Austria)], Seewald, Eric [Columbia Univ., New York, NY (United States)], Kundu, Asish K. [Brookhaven National Laboratory (BNL), Upton, NY (United States). National Synchrotron Light Source II (NSLS-II)] (ORCID:0000000321991053), Cui, Zhi-Hao [Columbia Univ., New York, NY (United States)] (ORCID:0000000273894063), Schertenleib, Till [Columbia Univ., New York, NY (United States); Ecole Polytechnique Federale Lausanne (EPFL) (Switzerland)] (ORCID:0000000349895821), Huang, Chun-Ying [Columbia Univ., New York, NY (United States)], Shao, Yinming [Columbia Univ., New York, NY (United States); Pennsylvania State Univ., University Park, PA (United States)], Qiu, Siyuan [Columbia Univ., New York, NY (United States)], Trovatello, Chiara [Columbia Univ., New York, NY (United States)] (ORCID:0000000281509743), Chica, Daniel G. [Columbia Univ., New York, NY (United States)], Huang, Xiong [Columbia Univ., New York, NY (United States)] (ORCID:0000000320358387), Song, Xiaoyu [Columbia Univ., New York, NY (United States)] (ORCID:0000000333840527), Koch Liston, André [Columbia Univ., New York, NY (United States)], Ziebel, Michael E. [Columbia Univ., New York, NY (United States)] (ORCID:0000000318578292), Vescovo, Elio [Brookhaven National Laboratory (BNL), Upton, NY (United States). National Synchrotron Light Source II (NSLS-II)], Delor, Milan [Columbia Univ., New York, NY (United States)] (ORCID:0000000294809235), Schuck, P. James [Columbia Univ., New York, NY (United States)], Reichman, David R. [Columbia Univ., New York, NY (United States)] (ORCID:0000000252655637), Zhu, Xiaoyang [Columbia Univ., New York, NY (United States)], Billinge, S. J. L. [Columbia Univ., New York, NY (United States)] (ORCID:0000000297344998), Basov, Dmitri N. [Columbia Univ., New York, NY (United States)], Pasupathy, Abhay N. [Columbia Univ., New York, NY (United States); Brookhaven National Laboratory (BNL), Upton, NY (United States)] (ORCID:0000000227440634), Roy, Xavier [Columbia Univ., New York, NY (United States)] (ORCID:0000000288500725). 2025-09-22. Chemical Control of Symmetry and Bandgap in Tungsten Oxyhalide van der Waals Semiconductors. https://doi.org/10.1021/jacs.5c12238

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The transition to a flexible and reliable energy infrastructure, using electro-thermal energy generation technologies such as geothermal, concentrated solar power, and nuclear, usually demands simultaneous advancement of thermal energy storage (TES) to support on-demand electricity generation and industrial applications while mitigating the inherent intermittency of renewable energy sources and power outages from direct energy generation. Among TES technologies, thermochemical energy storage (TCES) based on calcium looping emerges as a compelling high-power energy storage candidate due to its high reaction enthalpy, compatibility with elevated operating temperatures, and abundance of low-cost materials. However, the long-term durability of calcium-based sorbents for TCES is hindered by surface sintering and particle aggregation, leading to performance degradation over repeated thermal cycles. This study explores a moisture hydration-based strategy to regenerate a degraded calcium sorbent and mitigate performance degradation for long duration TCES. The addition of moisture transforms calcium oxide into calcium hydroxide and produces intercalation water layers, associated with a regenerated surface area and reduced calcium oxide crystallite size. Both these effects are beneficial in restoring the sorbents' reactivity for carbonization. Additionally, an optimized hydration-assisted reactivation protocol balances the recovered energy storage capacity with heating penalty required for moisture removal from hydrated samples, resulting in an enhanced energy storage capacity up to 176% compared to benchmark sorbents that undergo cycling without reactivation after 60 cycles. In conclusion, these results highlight the potential of hydration-assisted reactivation to enhance the long-term performance of TCES, providing an effective pathway to advancing electro-thermal storage technologies.

36 MATERIALS SCIENCE↗