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1. Surface Entropy Mediated Hydrogen Spillover on Au/TiO ₂ : Influences of Strongly Adsorbed Water on H ₂ Adsorption Thermodynamics

   https://doi.org/10.1021/jacs.5c06813  

   Yun, Tae Yong; Battiste, Audrey M; Pathickal_Abraham, Angela; Hart, Kelle D; Chandler, Bert D (August 2025, Journal of the American Chemical Society)

   Hydrogen spillover, a poorly understood adsorption phenomenon, plays an important role in hydrogen storage, catalytic hydrogenation, and energy conversion processes. While widely invoked to explain anomalous observations, the fundamental mechanisms underlying spillover remain under debate, particularly regarding the influence of surface adsorbates, such as water. In this study, we investigate how strongly adsorbed water (SAW) impacts hydrogen spillover (H*) on Au/TiO2 catalysts using in situ Fourier transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA). By carefully correlating IR and TGA data, we quantify the relationship between water coverage and spillover. At low to moderate temperatures (<200 °C), SAW resides primarily on Ti Lewis acid sites, while hydrogen spillover is associated with surface hydroxyl groups. Our findings reveal that even though H* and SAW do not directly compete for surface adsorption sites, SAW suppresses H*. Van’t Hoff studies indicate SAW suppresses spillover by modifying the surface entropy of the titania, presumably by perturbing multiple proton transfer equilibria across the support surface. Maintaining constant water and hydroxyl coverage over a modest temperature range allowed for the determination of reliable thermodynamic parameters for hydrogen spillover on titania, yielding a slightly exothermic heat of adsorption (−7 ± 1 kJ/mol H*). These insights highlight the indirect role that surface water can play in catalytic reactions involving hydrogen spillover and offer a new perspective on catalyst design and optimization for hydrogen-involved reactions. This work also highlights the importance of considering the entropy of oxide surfaces in understanding catalysis over oxides. 

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2. Electronic modulation of metal-support interactions improves polypropylene hydrogenolysis over ruthenium catalysts

   https://doi.org/10.1038/s41467-022-32934-5  

   Kots, Pavel A.; Xie, Tianjun; Vance, Brandon C.; Quinn, Caitlin M.; de Mello, Matheus Dorneles; Boscoboinik, J. Anibal; Wang, Cong; Kumar, Pawan; Stach, Eric A.; Marinkovic, Nebojsa S.; et al (September 2022, Nature Communications)

   Abstract Ruthenium (Ru) is the one of the most promising catalysts for polyolefin hydrogenolysis. Its performance varies widely with the support, but the reasons remain unknown. Here, we introduce a simple synthetic strategy (using ammonia as a modulator) to tune metal-support interactions and apply it to Ru deposited on titania (TiO₂). We demonstrate that combining deuterium nuclear magnetic resonance spectroscopy with temperature variation and density functional theory can reveal the complex nature, binding strength, and H amount. H₂activation occurs heterolytically, leading to a hydride on Ru, an H⁺on the nearest oxygen, and a partially positively charged Ru. This leads to partial reduction of TiO₂and high coverages of H for spillover, showcasing a threefold increase in hydrogenolysis rates. This result points to the key role of the surface hydrogen coverage in improving hydrogenolysis catalyst performance. 

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3. Continuous flow synthesis of phase transition-resistant titania microparticles with tunable morphologies

   https://doi.org/10.1039/D0RA01442G  

   Campbell, Zachary S.; Jackson, Daniel; Lustik, Jacob; Al-Rashdi, Amur K.; Bennett, Jeffrey A.; Li, Fanxing; Abolhasani, Milad (February 2020, RSC Advances)

   Titania microspheres have attracted substantial attention for a variety of applications, including ion scavenging, catalysis, and energy generation, though most synthetic techniques are limited to a few basic morphologies and narrow size ranges. Here, an intensified microfluidic strategy for continuous synthesis of anatase titania microspheres is presented. In-flow photo crosslinking, incorporated with a flow reactor and polar aprotic solvent, enables access to precursor compositions up to an order of magnitude higher than those previously reported, with size tunability approaching two orders of magnitude. Morphological and surface area effects associated with precursor composition are explored, resulting in hollow, yolk–shell, macroporous, and dense titania microspheres containing no detectable rutile phase and possessing surface areas exceeding 350 m 2 g −1 post calcination. Furthermore, effects of calcination temperature and time on the surface area, crystallinity and phase composition, and morphology of the synthesized titania microspheres are studied in detail. The synthesized microspheres are shown to remain completely in the anatase phase, even at temperatures up to 900 °C, far beyond the expected phase transition temperature. Thus, the breadth of attainable morphologies, specific surface areas, and phase compositions present a variety of intriguing substrate candidates for such applications as heterogeneous (photo) catalysis, adsorption and ion capture, electrochemistry, and photovoltaics. 

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4. First-principles study of hydrogen storage application of Ti3C2Tx monolayer MXene

   https://doi.org/10.1016/j.ijhydene.2024.01.136  

   Chu, Yi Zhi; Lau, Kah Chun (February 2024, International Journal of Hydrogen Energy)

   MXene, with its high aspect ratio and adjustable surface properties, has garnered significant attention in the realm of hydrogen storage research. For the first time, considering a ternary/quaternary mixed terminated MXene surface, the authors have investigated comprehensively the hydrogen storage potential of two-dimensional (2D) titanium carbide Ti3C2Tx monolayer MXene using density functional theory (DFT). By considering mixed terminated surfaces, this study indicated the locally induced dipole due to the mixed termination is beneficial in facilitating hydrogen adsorption with stronger average adsorption energies than that of the uniform F-/O-/OH-/H-terminated surfaces. The authors estimated a compelling average H2 surface adsorption energy on the ternary mixed termination and total surface storage capacity to be −0.14 eV/H2 and ∼2 wt% H2, which is comparable to that of the metal-organic frameworks (MOFs). This study also reveals the importance of the local surface chemistry effects on hydrogen adsorption. 

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5. Exploring adsorption of neutral aromatic pollutants onto graphene nanomaterials via molecular dynamics simulations and theoretical linear solvation energy relationships

   https://doi.org/10.1039/C8EN00575C  

   Wang, Ya; Comer, Jeffrey; Chen, Zhongfang; Chen, Jingwen; Gumbart, James C. (January 2018, Environmental Science: Nano)

   Predicting adsorption of organic pollutants onto graphene nanomaterials is not only useful for exploring their potential adsorbent applications, but also helpful for better understanding their fate and risks in aquatic environments. Herein molecular dynamics (MD) simulations and theoretical linear solvation energy relationships (TLSERs) were employed to construct prediction models for adsorption of neutral organic pollutants onto graphene and graphene oxides. The MD simulations for adsorption of 43 aromatic compounds onto graphene and diverse models of graphene oxides with various functional groups (hydroxyl, epoxy and carbonyl) demonstrate that graphene has a stronger affinity for the aromatic compounds than graphene oxides. The hydroxyl and carbonyl groups of graphene oxides were found to form hydrogen bonds with the aromatic adsorbates, while epoxy groups did not. TLSER models were developed for predicting the adsorption equilibrium coefficients ( K ) onto graphene and graphene oxide nanosheets. In the graphene prediction model, H-donating ability ( ε α ) and dispersion/hydrophobic interactions ( V ) have significant effects on log  K values, while in the graphene oxide model, ε α is the most influential factor on log  K values. The models provide in silico approaches for predicting adsorption affinities onto graphenic nanomaterials. 

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