Self-Assembled Gallium Sulfide (GaS) Heterostructures Enabling Efficient Water Splitting and Selective Ammonia Sensing

Boukhvalov D.W. DOlimpio G. Dadiani T. Sharma J. Elameen A.A.A. Zenone S. Rosmus M. Gürbulak B. Çepni E. Llobet E. Magnano E. Bondino F. Duman S. Politano A.
19 November 2025 John Wiley and Sons Inc

Advanced Functional Materials
2025 #35 Issue 47

Herein, a comprehensive validation of the catalytic and sensing capabilities of gallium sulfide (GaS). This study focuses on the self-assembled heterostructure formed by GaS with its native oxide, revealing novel insights into the crucial role of defects, strain, and surface oxide phases in optimizing the behavior of 2D materials for catalytic and sensing applications. Although the energy barrier for water dissociation on pristine GaS surfaces is prohibitive (+419.3 kJ mol⁻¹), surface sulfur vacancies considerably reduce this barrier, transforming defective GaS (GaS_x) into an efficient catalyst for the hydrogen evolution reaction (HER) in alkaline media. Water dissociation is energetically favorable at room temperature on GaS_0.96 surfaces (−147.6 kJ mol⁻¹). Correspondingly, the differential free energy for HER on GaS_0.96 in an alkaline medium is found to be −1.56 eV for the hydroxyl adsorption step and +1.28 eV for the desorption step, while all reaction steps are exothermic for its implementation as a catalyst for oxygen evolution reaction (OER). These theoretical models and surface-science experiments confirm that exposure of GaS surfaces to ambient conditions leads to the inevitable formation of a self-assembled nanoscale (≈3 nm thick) oxide skin. This native oxide layer stabilizes the surface and, moreover, it also significantly enhances its catalytic and sensing properties by providing additional active sites and improving charge transfer dynamics. The exceptional sensitivity (response of 18% at T = 150 °C) and selectivity for detecting ammonia (NH₃) are attributed to both its high affinity for chemisorption and the significant charge-transfer interactions that enhance the sensor response.

2D materials , ammonia sensing , DFT calculations , hydrogen evolution reaction , X-ray photoelectron spectroscopy (XPS)

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College of Science, Institute of Materials Physics and Chemistry, Nanjing Forestry University, Nanjing, 210037, China
Department of Physical and Chemical Sciences, University of LAquila, via Vetoio, LAquila (AQ), 67100, Italy
Universitat Rovira i Virgili, MINOS, Avda. Països Catalans, 26, Tarragona, 43007, Spain
Department of Applied Science and Technology, Polytechnic University of Turin, Corso Castelfidardo, 39, Turin, 10129, Italy
National Synchrotron Radiation Center SOLARIS, Jagiellonian University, Czerwone Maki 98, Krakow, PL-30392, Poland
Department of Physics, Faculty of Sciences, Atatürk University, Erzurum, 25240, Turkey
Department of Electrical and Electronics Engineering, Faculty of Engineering, Atatürk University, Erzurum, 25240, Turkey
Consiglio Nazionale delle Ricerche (CNR) - Istituto Officina dei Materiali (IOM), Area Science Park S.S. 14 km 163.5, Trieste, 34149, Italy
Basic Sciences Department, Faculty of Sciences, Erzurum Technical University, Erzurum, 25050, Turkey
Institute of Physics and Technology, Satbayev University, Ibragimov str. 11, Almaty, 050032, Kazakhstan

College of Science
Department of Physical and Chemical Sciences
Universitat Rovira i Virgili
Department of Applied Science and Technology
National Synchrotron Radiation Center SOLARIS
Department of Physics
Department of Electrical and Electronics Engineering
Consiglio Nazionale delle Ricerche (CNR) - Istituto Officina dei Materiali (IOM)
Basic Sciences Department
Institute of Physics and Technology

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