Ga-Pt bimetallic catalysts for propane dehydrogenation: Synergy, stability and strategies for industrial advancement: A literature review

 Corresponding author: Umah Nnamdi Jeremiah Copyright © 2025 Author(s) retain the copyright of this article. This article is published under the terms of the Creative Commons Attribution Liscense 4.0. Ga-Pt bimetallic catalysts for propane dehydrogenation: Synergy, stability and strategies for industrial advancement: A literature review Umah Nnamdi Jeremiah 1, *, Anyanwu Solomon Nonso 2, Udie Linus Ugbong 2 and Ucheaga P. Uchenna 3 1 Department of Physical chemistry, National University of Science and Technology MISIS Moscow, Russia. 2 Department of Materials Science of Semiconductors and Dielectrics, National University of Science and Technology MISIS Moscow, Russia. 3 Virginia Commonwealth University, Richmond, United States. World Journal of Advanced Research and Reviews, 2025, 27(01), 2728-2744 Publication history: Received on 23 June 2025; revised on 28 July 2025; accepted on 31 July 2025 Article DOI: https://doi.org/10.30574/wjarr.2025.27.1.2819 Abstract The growing global demand for propylene, a key petrochemical feedstock, has intensified research into sustainable production methods beyond conventional cracking processes. Among emerging technologies, propane dehydrogenation (PDH) has gained prominence as a clean and direct route to propylene. This review critically examines the recent advances in gallium-platinum (Ga-Pt) catalysts, which have demonstrated exceptional performance in PDH. The synergy between Gallium and Platinum improves selectivity, suppresses coke formation, and enhances catalyst stability by isolating Platinum atoms and electronically modifying active sites. Developments such as single-atom intermetallics, Supported Catalytically Active Liquid-Metal Solutions (SCALMS), and electronic self-recovery mechanisms are discussed in detail. This review also explores advanced synthesis and characterization techniques, including Atomic Layer Deposition, X-ray Diffraction, Transmission Electron Microscopy, X-ray Photoelectron Spectroscopy, and operando spectroscopy, that elucidate active site structure and dynamics. Benchmarking data reveal Ga-Pt systems consistently outperform traditional Pt-Sn catalysts in activity, selectivity, and resistance to deactivation. The integration of machine learning and high-throughput screening has accelerated the design of next-generation catalysts. Finally, the industrial and environmental implications, challenges in scale-up, and future directions including ternary alloys and autonomous discovery platforms are addressed. This comprehensive analysis highlights Ga-Pt catalysis as a blueprint for rational catalyst design in PDH and beyond. Graphical Abstract World Journal of Advanced Research and Reviews, 2025, 27(01), 2728-2744 2729 Keywords: Propane Dehydrogenation; Bimetallic Catalysts; Ga-Pt Synergy; Single-Atom Catalysis; DFT; Machine Learning 1. Introduction The demand for propylene has sky-rocketed due to its recently acquired status as the most used petrochemical and polymer industry building block and this has created a widening difference between industrial production and its current demand. It has gained the interest of academia and industries which has led to numerous researches towards the direct manufacture of propylene from propane [1, 2]. Propylene serves as a crucial building block during the production of numerous polymers, fuels, and chemicals. A significant proportion of global propylene demand exists for the production of polypropylene through synthesis. Propylene is also used in the manufacturing of key compounds such as cumene, propylene oxide, acrylic acid, and isopropyl alcohol. In the petrochemical sector, propylene finds uses in the high-octane gasoline production as it aids in the processes of alkylation, catalytic polymerization, and dimerization [3]. This has led to the development of important production technologies, among which the catalytic dehydrogenation of abundant and low-cost propane (PDH) has become the best alternative. Propane dehydrogenation (PDH) is an important process for the production of propylene, which offers a clean way to dehydrogenate propane into propylene that is utilized in the manufacturing of plastics, synthetic materials, and other chemical products. With the growing need for propylene, PDH is in the front line of enhancing production efficiency as well as acting in fulfilling supply needs, while also offering an opening to overcome traditional Pt-based catalyst challenges such as deactivation and sintering [4,5,6] This reaction however is associated with a high thermal absorption and demands that it is carried out under high temperature and low-pressure conditions which may enable the occurrence of side reactions like thermal cracking, leading to the light alkane formation and coke which are likely to produce rapid catalyst deactivation [7]. Achieving a high propylene selectivity and long-term stability at the high temperatures (550–700 °C) required for thermodynamically favorable conversion poses a challenge to this process. C3H8 ⇌ C3H6 + H2 𝛥𝐻293.15 = +124.3 kJ/mol [8] The majority of propylene has traditionally been produced as a byproduct of steam cracking and fluid catalytic cracking. These sources, however, have increasingly been unable to match the growing global demand. As a result, dedicated or "on-purpose" production technologies have been developed, particularly exploiting the availability of shale gas. Some of the leading commercial processes for light alkane dehydrogenation include CATOFIN (by CB&I and ABB Lummus), Oleflex (by UOP Honeywell), and the STAR process (by ThyssenKrupp Uhde) [9]. The current industrial catalyst landscape is dominated by chromium oxide (CrOx/Al₂O₃) and platinum-tin (Pt–Sn/Al₂O₃) systems. While cost-effective, chromium oxide catalysts pose environmental risks due to the toxicity of Cr(VI) and suffer from rapid coking, Platinumbased catalysts are highly active for C–H bond activation but, in their monometallic form, are notoriously unselective, promoting deep dehydrogenation, hydrogenolysis, and coking, which leads to rapid deactivation [10]. The addition of a second, non-noble metal promoter like tin (Sn) mitigates these issues by breaking up large Pt ensembles and modifying its electronic properties, forming the basis of technologies like the UOP Oleflex™ process [3]. In this review, the exploration of gallium (Ga) as a promoter for Pt has emerged as a particularly fruitful area of research. Early studies demonstrated that Ga could significantly enhance propylene selectivity and catalyst lifetime compared to both monometallic Pt and conventional Pt–Sn systems [11]. The Pt-Ga synergy creates an unparalleled catalytic efficiency that maximizes activity and long-term stability in propane dehydrogenation (PDH), augmenting activity and stability. Such effectiveness is a result of the singular interaction between Pt and Ga, which enhances the electronic structure and geometry of the catalyst. Such adjustments enhance hydrogen splitting and help resist coke formation, resulting in a more efficient and stable catalyst [12]. 2. Basic Chemistry of Individual Metals 2.1. Gallium In its metallic form or as an oxide (Ga₂O₃), gallium is largely inactive for propane C-H bond activation at typical PDH temperatures but supported gallium oxide has been studied as a catalyst for light alkane dehydrogenation [13]. Gallium World Journal of Advanced Research and Reviews, 2025, 27(01), 2728-2744 2730 is more selective than Pt but its activity is generally too low for industrial application. This stems from the acidic and basic property of Gallium oxide catalyst which tends to greatly affect its catalytic activity and so, supported Gallium oxide catalyst tends to have a reduced acidity and is even more preferred than other catalysts [14]. 2.2. Platinum Platinum is exceptionally efficient at cleaving the strong C-H bonds in propane due to the favorable energy of its d-band center relative to the Fermi level, which facilitates strong interaction with hydrocarbon adsorbates [15]. However, this high reactivity tends to be of a great advantage. On the surface of Pt nanoparticles, contiguous multi-atom sites (ensembles) not only catalyze the desired first dehydrogenation step but also readily promote subsequent, undesired reactions such as • Hydrogenolysis: This is where the strong C-C bonds in propane or propylene can be cleaved, leading to the formation of methane and ethane which is a direct loss of valuable product. • Coking: The unsaturated surface species can polymerize and cyclize, eventually forming graphitic coke that physically blocks active sites and pores, causing rapid deactivation [16]. Consequently, a monometallic Pt/Al₂O₃ catalyst typically exhibits poor propylene selectivity (~80% or lower) and deactivates under industrial PDH conditions [17]. 3. Ga-Pt Synergy The remarkable performance of Ga-Pt catalysts arises from a complex interplay of effects that operate at different length scales, from atomic level electronic interactions to nanoscale structural dynamics. Table 1 summarizes the historical development of Ga-Pt PDH Catalysts Table 1 Historical Milestones in the Development of Ga-Pt PDH Catalysts Period Representative Work & Formulation Key Development/Outcome Reference Early 2000s Pt-Ga/Al₂O₃ prepared by successive impregnation First clear demonstration that adding Ga dilutes contiguous Pt sites, increasing propylene selectivity and slowing coking compared with monometallic Pt/Al₂O₃. [18] 20102015 Ga-Pt “SCALMS” (Supported Catalytically Active LiquidMetal Solutions) Liquid Ga wets Pt nanoparticles; the mobile Ga phase continually renews the Pt–Ga interface, giving high activity and exceptional coke resistance. [19] 20162019 Single-atom Pt locked in crystalline Pt-Ga intermetallic Atomically isolated Pt in a Pt-Ga matrix shows >98% propylene selectivity for over 100 hours at 600 °C, illustrating the "single-site in alloy matrix" concept. [20] 20202023 Electron-driven selfrecovery of sub-nano PtGa clusters Dynamic re-alloying under reaction conditions restores Pt– Ga ensembles; competitive adsorption on Pt-Gaδ+ sites lower the C–H activation barrier and suppresses deep dehydrogenation. [21] 20232025 H₂-pretreatment & redoxswing strategies for Ga–Pt SCALMS Mild H₂ treatment removes surface oxides, increases Ga⁰ content, and doubles time-on-stream stability without causing sintering. [22] 3.1. Electronic and Structural Interactions The most fundamental synergistic effect is the geometric isolation of Pt atoms by Ga atoms. By substituting Ga into the Pt lattice, large, contiguous Pt ensembles are broken up and the remaining isolated Pt single atoms or small clusters are still active for the initial C-H bond splitting in propane but are hindered from catalyzing the subsequent reactions of adsorbed propylene that lead to coke formation. This effect is the primary reason for the dramatic increase in propylene selectivity [20,23]. World Journal of Advanced Research and Reviews, 2025, 27(01), 2728-2744 2731 Alloying Ga with Pt induces significant electronic modification. Density Functional Theory calculations consistently shows that Ga being more electropositive, donates electron density from its SP-band to the d-band of Pt. This charge transfer has two crucial consequences: Down-shift of the Pt d-band center: The Pt d-band center is lowered by 0.25-0.35 eV away from the Fermi level. This weakens the adsorption energy of key intermediates, particularly propylene. While the bond to propane is weakened slightly, the bond to propylene is weakened more significantly. This facilitates rapid desorption of the desired product before it can undergo further reaction, thereby boosting selectivity. Creation of Bifunctional Sites: The charge transfer results in slightly electron-rich Pt (Ptδ⁻) sites and partially positive Ga (Gaδ⁺) sites. This creates a bifunctional surface where Pt remains the primary center for C-H activation, while adjacent Ga sites can act as hydrogen acceptors or Lewis acid sites, potentially facilitating H-spillover and altering the reaction pathway [22,24]. 3.2. Mechanistic Insights from Advanced Studies Kinetics and DFT: Combined kinetic and computational studies have provided a detailed picture of the reaction mechanism. DFT calculations show that Ga incorporation can lower the activation barrier for the rate-limiting β-hydride elimination step by 0.1-0.2 eV, while simultaneously increasing the energy barrier for C-C cleavage [24]. This explains how Ga-Pt catalysts can be both more active and more selective than their Pt-Sn counterparts. The models also predict a significant reduction in the binding energy of carbonaceous species on Pt-Ga surfaces compared to pure Pt rationalizing the enhanced coke resistance [25]. In Situ/Operando Spectroscopy: The dynamic nature of Ga-Pt catalysts under reaction conditions has been revealed by powerful operando techniques. Operando Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) coupled with mass spectrometry has been used to monitor surface species and gas-phase products simultaneously. These studies have confirmed the electronic modification of Pt by observing a red-shift in the vibrational frequency of adsorbed CO, a classic indicator of increased electron back-donation from the metal [10]. Furthermore, operando studies have shown that proximal Ga⁺-H⁺ pairs, formed during the reaction, are exceptionally active sites, exhibiting turnover frequencies up to 15 times higher than isolated Ga⁺ sites [26]. Dynamic and Liquid-Phase Behavior: A paradigm shift occurred with the introduction of Supported Catalytically Active Liquid-Metal Solutions (SCALMS). In this concept, solid Pt nanoparticles are suspended in a thin film of molten Ga on a support [19]. This fluidic environment continuously exposes fresh Pt-Ga active sites and is thought to dissolve or sweep away coke precursors, leading to extraordinary stability. More recent work has shown that even solid sub-nanometer Pt-Ga clusters exhibit dynamic behavior, undergoing "electron-driven self-recovery" where the alloy can de-alloy and re-alloy under redox cycles, maintaining high activity [21]. 4. Catalyst Synthesis & Characterization The specific architecture of the Ga-Pt interface is critical to its performance, and a variety of synthesis methods have been developed to control it. 4.1. Common Preparation Routes Successive/Co-impregnation: The traditional method involves impregnating a high-surface-area support like γ-Al₂O₃ or ZSM-5 zeolite with aqueous solutions of Pt and Ga precursors (e.g., [Pt(NH3)4]Cl2.H2O and Ga(NO₃)₃), followed by calcination and reduction. This method is simple but often leads to poorly controlled particle sizes and phase heterogeneity [27] Atomic Layer Deposition (ALD): ALD offers layer-by-layer control over the deposition of Ga and Pt, enabling the synthesis of core-shell structures or finely dispersed alloys with unparalleled precision [28] SCALMS Preparation: These catalysts are typically made by impregnating a support with Ga, followed by the addition of a Pt precursor. Upon heating, the Ga melts and dissolves the Pt, forming the active liquid film [19]. 4.2. Advanced Characterization for Probing the Active Site Characterization techniques employs the use of well-built devices in material science which enables researchers to analyze and understand the characteristics, properties and performances of various materials which ranges from World Journal of Advanced Research and Reviews, 2025, 27(01), 2728-2744 2732 nanomaterials, solar cells, supercapacitors, and catalysts. The processes involved helps in unveiling the structural, chemical, and physical properties of materials necessary for optimizing their applications. Some characterization techniques employed includes X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), specific surface area measurements using the Brunauer–Emmett–Teller (BET) method, and X-ray Absorption Fine Structure (XAFS) analysis, X-ray photoelectron spectroscopy (XPS), temperature-programmed desorption of ammonia (NH3-TPD), energy dispersive spectroscopy (EDS), thermogravimetric analysis (TG), [29,30,31]. 4.2.1. X-Ray Diffraction Analysis (XRD) X-ray diffraction (XRD) is a standard technique that is widely applied in heterogeneous catalysis to determine the phase composition, atomic structure, and size of a materials crystals [32]. The XRD peaks result from the constructive interference of a monochromatic X-ray beam at the specified angle, as illustrated in the figure below [33]. However, the position, intensity, and width of the peak mostly depend on the characteristics of the atomic structure. It applies the principle of diffraction, where X-rays interact with the atoms in the crystal lattice of the material and produces a diffraction pattern that provides important information which aids the identification of a material's structure. Figure 1 Phenomenon of constructive interference observed during X-ray diffraction (XRD) [34] 4.2.2. Bragg’s Law and Diffraction Principle The Bragg’s Law, which describes the conditions for constructive interference of X-rays diffracted from crystal planes. Bragg’s Law is expressed as: where: n is an integer (order of diffraction), λ is the wavelength of the X-rays, d is the interplanar spacing between atoms in the crystal lattice, θ is the angle of incidence and diffraction [35]. This law explains how X-rays diffracted from different atomic planes interfere constructively when the path difference between the waves is an integer multiple of the wavelength [36]. 4.2.3. X-ray Generation and Instrumentation X-rays are produced using an X-ray tube, where high-energy electrons strike a metal target (e.g., copper or molybdenum) and produces X-rays of a given. An XRD device consists of an X-ray Source, a Collimator, Sample Holder and a detector [37]. World Journal of Advanced Research and Reviews, 2025, 27(01), 2728-2744 2733 Figure 2 A Schematic representation of a basic Bragg-Brentano (BB) instrument configuration, angular resolution is determined by the receiving slit opening and the radius of the measuring circle [38] 4.2.4. Diffraction Pattern and Analysis On interaction with a crystalline sample, X-rays diffract at specific angles and creates a diffraction pattern which is a blueprint of the material’s crystal structure and the various peak positions and peak intensities helps us understand the Phases present, the crystal Structure, structural Parameters such as grain size, strain, and defects [39]. XRD is most effective for materials with a well-defined crystal structure and provides limited information for amorphous substances. This technique requires careful sample preparation, especially for thin films and nanomaterials [40]. 4.2.5. Scanning Electron Microscopy (SEM) Scanning Electron Microscopy (SEM) is a research method that enables researchers to study a specimen's surface topography and chemical composition. However, in its simplest form, it uses a beam of electrons and SEM interacts with some atoms of the sample to emit some signals and information obtained from the signals can serve to provide the important information of the material characteristics and arrangement. By adjusting the control of the electron beam, material density differences in the sample can be examined precisely. This technique is remarkable due to its broad application in multiple sectors, ranging from materials science to semiconductor manufacturing to research in biology. The combination of high-resolution images with precise compositional information at the same times makes SEM especially useful for failure analysis, quality control as well as more complex scientific inquiries [41,42,43] World Journal of Advanced Research and Reviews, 2025, 27(01), 2728-2744 2734 Figure 3 SEM (at MISIS university) Figure 4 Schematic diagram of the scanning electron microscope [44]. 4.2.6. Transmission Electron Microscopy (TEM) The transmission electron microscopy or TEM for its acronym in English, is a visual analytical technique which uses an electron beam, positioned on a sample to get a magnified version of the material over a fluorescent screen [45]. TEM has been applied and used for both structural and morphological characterization of different materials as well as catalysts as it supplies detailed information about the size, shape, and distribution of nanoparticles which are necessary fundamentals for understanding the behaviors of materials as well as a material catalytic activity [46]. TEM has generally been used for studying the morphology of nanomaterials, nanomaterials-polymer interface, microanalysis by characteristic X-rays, localized chemical composition of nanomaterial or thin film, electron diffraction patterns, In situ temperature changes in the sample, differentiating phases of nanomaterials by using electron energyloss spectroscopy, chemical mapping of an area of interest of the sample, live dynamics of the nanomaterials in liquid phase by using latest liquid-cell TEM holder [47]. A drawback of this technique is that it is time consuming and proceeds with little efficiency in terms of the preparation of the sample due to financial constraints [45]. World Journal of Advanced Research and Reviews, 2025, 27(01), 2728-2744 2735 Figure 5 Transmission electron microscope Illustration [45] 4.2.7. X-Ray Photoelectron Spectroscopy (XPS) XPS has found great application in surface analysis of materials cutting across areas such as corrosion, catalysis, electronics, nanomaterials, biomedicine, mineral processing, automotive and aerospace etc. Most often, the technique is used to obtain the chemical composition, surface functionalization, adsorbates, layer thickness and in some cases even particle size of nanomaterials [48]. It employs the use of X-rays which knocks off photoelectrons from a material and then measures the kinetic energy of the photoelectrons. This kinetic energy measured allows researchers to determine the binding energies of the electrons which are specific to different elements and their chemical environments. The technique is particularly useful for analyzing surfaces and thin films and this makes XPS ideal for studying surface phenomena such as corrosion, catalysis, and the properties of nanomaterials [49,50]. This method of spectroscopic analysis can be used to confirm the presence of all elements with exception to hydrogen and helium which have detection limits ranging between 0.1%–1% approximately. XPS is extremely surface sensitive and so necessary care needs to be employed to avoid surface contamination [51]. Figure 6 Schematic view of the XPS instrumentation [52] World Journal of Advanced Research and Reviews, 2025, 27(01), 2728-2744 2736 4.2.8. The Brunauer-Emmett-Teller (Bet) Method The BET method is a major technique applied to access and measure the specific surface area of materials (porous materials) more especially solids which may be amorphous in nature like activated carbons or may possess crystalline structure like metalorganic frameworks (MOFs) and covalent organic frameworks (COFs) [53]. The specific surface area of a material is an essential characteristic that impacts its performance in applications such as catalysis, gas adsorption, and chemical reactions. This technique enables the measurement of the surface area of materials with precision and consistency and is used greatly in scientific, industrial, and quality assurance fields. The BET method begins by an exposure of the solid material to a gas at a known temperature and pressure which is increased gradually with the quantity of adsorbed gas recorded at each pressure attained. The data obtained are then used to plot the BET isotherm which is a graph of the amount of adsorbed gas (typically nitrogen) against the relative pressure and the characteristic shapes and linear region at intermediate pressures obtained is utilized for analysis [54]. 4.2.9. The BET theory The fundamental element of the BET theory is associated with the adsorption of a gas on the material’s surface. The working principle of the BET is derived from the Langmuir theory of multi-layer adsorption of gas molecules on a solid surface [55]. This theory is rooted on some assumptions that may not be ideal for determining the surface area of microporous materials such as MOFs and has such intrigued the curiosity of many researchers who have delved into the investigation of the suitability of this method [56] The assumptions of the BET theory are as adopted from [55,57] are • Adsorption occurs on a uniform/homogeneous surface and all the gas molecules in the first adsorbed layer have equal energies of adsorption, • The uppermost molecules in adsorbed stacks are in dynamic equilibrium with the vapor, • The differential energy of physisorption for the first layer, E1 is higher than the heat of liquefaction, EL, • There is no lateral interaction between adsorbate molecules in the same layer, and • The second and subsequent layers formation start before the completion of the first layer. It has been observed that the effective predictability of the number of adsorbate molecules available in the outermost covering of the solid guarantees the success of these assumptions. Operando DRIFTS: As mentioned, this technique links surface chemistry with catalytic activity in real-time. For example, in a study of La-promoted PtGa/Al₂O₃, operando DRIFTS showed that the presence of lanthanum facilitated faster removal of surface hydrogen, which correlated with a lower rate of coke formation observed by thermogravimetric analysis (TGA) [26]. The combination of these techniques provides a powerful "triangulation" method, correlating atomic structure (STEM), electronic state (XAFS), and surface reactivity (DRIFTS) with macroscopic performance (activity, selectivity, stability). 5. Performance Benchmarking The ultimate measure of a catalyst's utility is its performance relative to established and emerging alternatives. 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