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Nitric oxide conversion to nitrogen on the W3O6 cluster through the ammonia selective catalytic reduction reaction: a DFT study
(2026-05-05)
Aziz, Hafiz Aji
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Daengngern, Rathawat
Nitric oxide (NO), a harmful byproduct of fossil fuel combustion, can be effectively removed via the Selective Catalytic Reduction (SCR) process using ammonia (NH<inf>3</inf>), producing N<inf>2</inf> and H<inf>2</inf>O. This study investigates the SCR mechanism of NO by NH<inf>3</inf> over the W<inf>3</inf>O<inf>6</inf> cluster using the DFT/M06-L/LANL2DZ-ECP/aug-cc-pVTZ method. Chemisorption of NO on W<inf>3</inf>O<inf>6</inf> forms a stable W<inf>3</inf>O<inf>6</inf>–NO intermediate (−34.47 kcal·mol−1), initiating the reaction, followed by NH<inf>3</inf> adsorption (−25.14 kcal·mol−1). The overall mechanism includes: (i) NH<inf>3</inf> adsorption and dehydrogenation, (ii) NO adsorption and nitrosamine formation, (iii) nitrosamine rearrangement, (iv) N<inf>2</inf> and H<inf>2</inf>O formation, and (v) gas desorption and catalyst regeneration. Nitrosamine formation is identified as the rate-determining step, with an activation barrier of 33.45 kcal·mol−1. The calculated rate constant (1.88 × 10−12 s−1) from Harmonic Transition State Theory (HTST) confirms its critical role in controlling the SCR reaction kinetics.
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Bridging the Gap in Understanding the Mechanism of NH3 Formation During NO Reduction by CO in the Presence of H2O Over Rh/Al2O3 Catalysts: DFT Study
(2026-02-01)
Wangphon, Chanthip
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Khajondetchairit, Patcharaporn
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Rittiruam, Meena
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Ektarawong, Annop
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Alling, Björn
Ammonia (NH<inf>3</inf>) formation from nitric oxide (NO) and carbon monoxide (CO) in the presence of water is a promising pathway for low-temperature NO<inf>x</inf> reduction. In this work, density functional theory (DFT) calculations were used to investigate the mechanism of NH<inf>3</inf> formation on a Rh(111)/γ-Al<inf>2</inf>O<inf>3</inf>(110), in which the Rh(111) and γ-Al<inf>2</inf>O<inf>3</inf>(110) were considered separately. NO readily dissociates on the Rh site, forming N*, which reacts with CO to produce the key intermediate of NCO*. Meanwhile, water dissociates more easily on γ-Al<inf>2</inf>O<inf>3</inf>(110), providing H* species. The hydrolysis of NCO* can proceed via two pathways: on Rh(111), it forms HNCO, while on γ-Al<inf>2</inf>O<inf>3</inf>(110), it forms HNCOH*. Both intermediates subsequently decompose into NH* species, which are then hydrogenated to produce NH<inf>3</inf>. The Rh pathway is more favorable in both kinetics and thermodynamics, while the support mainly supplies hydrogen through water activation. These results suggest a dual-site mechanism in which Rh drives the main transformation, and γ-Al<inf>2</inf>O<inf>3</inf>(110) assists via hydrogen transfer. This work presents the individual roles of Rh and Al<inf>2</inf>O<inf>3</inf> surfaces in NO reduction with CO, producing NH<inf>3</inf>, which is relevant to catalytic behavior under humid conditions.
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Unraveling H2 dissociation in CO2 hydrogenation on frustrated Lewis pair-functionalized UiO–67: DFT and nuclear quantum effects
(2025-12-04)
Yodsin, Nuttapon
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Udagawa, Taro
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Daengngern, Rathawat
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Jungsutthiwong, Siriporn
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Tachikawa, Masanori
Understanding hydrogen (H<inf>2</inf>) activation is fundamental to developing efficient CO<inf>2</inf> hydrogenation catalysts. Thus, in this study, we examine H<inf>2</inf> dissociation and subsequent CO<inf>2</inf> hydrogenation on 12 UiO–67 frameworks functionalized with frustrated Lewis pairs (FLPs), employing both conventional density functional theory (DFT) and multicomponent DFT (MC_DFT) to account for nuclear quantum effects (NQEs). The results reveal that all FLP–MOFs lower the H<inf>2</inf> activation barrier through heterolytic cleavage, with NQEs further reducing the barriers—most notably in systems containing electron-donating groups (EDGs), where pronounced H–H bond elongation characterizes the transition state. Conversely, FLPs bearing strong electron-withdrawing groups stabilize the 2H adsorption state, rendering H<inf>2</inf> dissociation thermodynamically favorable but suppressing CO<inf>2</inf> hydrogenation owing to excessively strong hydrogen binding. Strong correlations are observed among H<inf>2</inf> dissociation energies, CO<inf>2</inf> hydrogenation activation barriers, and FLP acidity, enabling catalytic performance prediction. Incorporating NQEs enhances these correlations, providing a refined descriptor for rational catalyst screening. Overall, this study highlights the critical role of NQEs in hydrogen activation and demonstrates that EDG-functionalized FLP–MOFs are particularly promising candidates for promoting H<inf>2</inf> activation and CO<inf>2</inf> conversion.
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Ultrasonic-driven synthesis of Cu-chlorophyllin-stabilized silver nanoparticles for high-efficiency antimicrobial surgical suture coatings
(2025-12-01)
Sombutjiraporn, Saran
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Mathaweesansurn, Arjnarong
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Daengngern, Rathawat
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Detsri, Ekarat
A novel Cu-chlorophyllin-stabilized silver nanoparticle (Ag0<inf>NPs</inf>-Chl<inf>Cu</inf>) with potent antimicrobial properties was synthesized for the first time using an ultrasonically driven chemical reduction approach. In this approach, Cu-chlorophyllin (Chl<inf>Cu</inf>) acts as a stabilizing ligand, while sodium borohydride functions as the chemical reductant. The formation mechanism of Ag0-NPs<inf>CHL</inf> was elucidated, revealing that ultrasonic irradiation facilitates the in situ reduction of Ag (I) and its subsequent incorporation into the Chl<inf>Cu</inf> complex. Four pyrrole rings coordinate with Ag0<inf>NPs</inf> through four nitrogen atoms, which serve as adsorption sites for the anchorage of Ag0-NPs<inf>CHL</inf>. Characterization by XPS revealed the presence of Ag-N bonding involving pyrrole units on the FCC structure of Ag0<inf>NPs</inf>. Ag0<inf>NPs</inf>-Chl<inf>Cu</inf> demonstrated a zeta potential of (-) 35.57±3.54 mV with a spherical shape and an average size of 6.72±1.72 nm, resulting in a stable colloidal dispersion with a monodispersed index. The synthesized Ag0-NPs<inf>CHL</inf> nanocomposites were subsequently deposited onto polyamide surgical sutures via an electrostatic Layer-by-Layer (LbL) self-assembly technique. The coated sutures exhibited >99.9 % antibacterial efficiency against E. coli (ATCC25922), S. aureus (ATCC25923), and A. baumanii (ATCC19606). While nanoparticle accumulation was observed in human primary epidermal keratinocyte (HEKa) cells, no cytotoxic effects were detected in the epidermis. This study highlights the effectiveness of Chl<inf>Cu</inf> as a dual stabilizing and coordinating agent for Ag⁰<inf>NPs</inf>, offering a promising approach for developing antimicrobial surgical materials.
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Theoretical investigation on the role of external oxygen facilitating oxidative dehydrogenation of hydrogen sulfide on Fe-based oxide catalysts
(2025-11-15)
Saelee, Tinnakorn
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Setasuban, Sorawee
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Noppakhun, Jakapob
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Rittiruam, Meena
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Khajondetchairit, Patcharaporn
The oxidative dehydrogenation (ODH) of hydrogen sulfide (H<inf>2</inf>S) is a critical process in biogas purification, enabling cleaner and more efficient utilization of renewable energy sources. This study employs density functional theory (DFT) and microkinetic modeling to investigate the role of external oxygen (O<inf>ext</inf>) in enhancing the catalytic performance of O<inf>2</inf>/α-Fe<inf>2</inf>O<inf>3</inf>(0 0 0 1) surfaces. The findings reveal that O<inf>ext</inf> significantly lowers the activation energy of key reaction steps, promotes more favorable reaction pathways, and mitigates sulfur poisoning by stabilizing lattice oxygen and suppressing the formation of oxygen vacancies. The unique electronic and structural properties of the O<inf>2</inf>/α-Fe<inf>2</inf>O<inf>3</inf>(0 0 0 1) surface facilitate improved catalyst activity and extended operational stability, addressing key challenges in sustainable energy technologies. The existence of the O<inf>ext</inf> can decrease the optimal temperature of ODH of H<inf>2</inf>S from >1150 K on the pristine α-Fe<inf>2</inf>O<inf>3</inf>(0 0 0 1) surface to 850 K on the O<inf>2</inf>/α-Fe<inf>2</inf>O<inf>3</inf>(0 0 0 1) surface. Furthermore, undergoing the ODH reaction to the steady state is 1.25 × 103 times faster than that of a lean α-Fe<inf>2</inf>O<inf>3</inf>(0 0 0 1) surface. Also, the amount of poisoned species of S* on the O<inf>2</inf>/α-Fe<inf>2</inf>O<inf>3</inf>(0 0 0 1) surface is lowered significantly. This work advances the design of robust catalysts for efficient H<inf>2</inf>S removal by providing a deeper understanding of catalytic behavior and deactivation mechanisms. The insights presented here contribute to cleaner energy production and environmental protection, bridging fundamental knowledge and practical applications in catalysis.
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Unlocking efficient CO2–to–methanol conversion on frustrated Lewis pair-functionalized UiO–67: A synergistic approach using DFT and SISSO
(2025-10-01)
Yodsin, Nuttapon
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Pimbaotham, Pimjai
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Maihom, Thana
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Daengngern, Rathawat
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Tachikawa, Masanori
Metal–organic framework-based catalysts demonstrate considerable promise for converting CO<inf>2</inf> into valuable chemicals, particularly when combined with Frustrated Lewis Pairs (FLPs) to enhance H<inf>2</inf> dissociation during hydrogenation reactions. This study employs density functional theory (DFT) calculations to investigate modified UiO–67 frameworks wherein FLPs are introduced via eight different functional groups (UiO–67–X) into the organic linker to facilitate H<inf>2</inf> activation during CO<inf>2</inf> hydrogenation to methanol (CH<inf>3</inf>OH). The reaction proceeds through three stages: (i) hydrogenation of CO<inf>2</inf> to formic acid (HCOOH), (ii) conversion of HCOOH to formaldehyde (HCHO), and (iii) hydrogenation of HCHO to CH<inf>3</inf>OH. This study specifically focuses on steps (ii) and (iii), analyzing the detailed reaction mechanisms using optimized molecular structures and Gibbs free energy calculations to acquire insights into methanol formation on UiO–67–X. During HCOOH conversion to HCHO, adsorbed H<inf>2</inf> undergoes heterolytic cleavage at the FLP sites, producing a proton (H+) and a hydride (H−) for subsequent HCOOH hydrogenation and dehydration. The energy barriers identified at this stage represent key kinetic limitations hindering efficient CO<inf>2</inf>-to-methanol conversion. Similarly, HCHO conversion to CH<inf>3</inf>OH proceeds via H<inf>2</inf> dissociation, followed by concerted H+/H− transfer. Among the tested UiO–67–X catalysts, UiO–67–B(CH<inf>3</inf>)<inf>2</inf> exhibits the highest catalytic activity for CO<inf>2</inf> hydrogenation to methanol. Kinetic analyses are performed to assess reaction rates across a relevant temperature range, highlighting the notable influence of functional groups on catalytic performance. Additionally, the Sure Independence Screening and Sparsifying Operator (SISSO) machine-learning approach is used to identify optimal physical descriptors and derive a predictive model for the energetic span (δG), considerably lowering the computational cost associated with full reaction pathway calculations. Statistical validation confirms the robustness of these predictions. Overall, these findings underscore the vital role of FLP-assisted H<inf>2</inf> dissociation in promoting CO<inf>2</inf> hydrogenation to CH<inf>3</inf>OH, with UiO–67–B(CH<inf>3</inf>)<inf>2</inf> serving as a promising catalyst.
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A proton transfer competition of 1,8-di(pyridin-2-yl)-9H-carbazole in excited-state intramolecular proton transfer through on-the-fly dynamic simulation
(2025-10-01)
Inporn, Wutthana
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Kungwan, Nawee
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Daengngern, Rathawat
Excited-state intramolecular proton transfer (ESIPT) of 1,8-di(pyridin-2-yl)-9H-carbazole (DPyCz) was investigated using static and excited-state dynamic simulations. Three-distinct configurations, each involving a different pyridyl moiety forming an intramolecular hydrogen bond, were identified to explore the competition in ESIPT. Additionally, slower PT, occurring at ∼200 fs, was found to depend on the competition between the pyridyl nitrogen atoms as acceptors. In contrast, DPyCz-B, which features only a single acceptor site, facilitated twice faster PT than that of DPyCz-A. Thus, our findings suggested that the ESIPT process of DPyCz is possibly governed by the interplay of intramolecular hydrogen bonding and excited-state charge redistribution.
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First-Principles Screening of 3d-Transition-Metal-Doped Hydrous Cobalt Phosphate Catalysts for Enhanced Oxygen Evolution Reaction
(2025-09-01)
Rittiruam, Meena
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Saelee, Tinnakorn
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Khajondetchairit, Patcharaporn
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Ektarawong, Annop
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Alling, Björn
Hydrous cobalt phosphate (CoPO) is a promising OER catalyst, but its activity is limited by poor electron transport and weak intermediate binding. This study reveals how 3d transition metal dopants can be used to tune these properties through first-principles calculations. Sc, Ti, V, and Cr improve catalytic activity by promoting electron transfer and stabilizing *O intermediates, while Mn, Fe, Cu, and Zn reduce performance. Among all candidates, Ni doping strikes the optimal balance, enhancing conductivity and providing moderate *O binding energy that minimizes overpotential. These trends follow electronic descriptors such as d-band center and electronegativity, and are validated by volcano plot analysis. Ni-CoPO emerges as the most effective design, offering a clear strategy for improving OER catalysts by controlling dopant identity and electronic structure.
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Experimental and Theoretical Exploration of Ultrafast Excited State Double Proton Transfer in 2,5-Bis(2-benzimidazolyl)hydroquinone
(2025-07-01)
Prommin, Chanatkran
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Chaihan, Komsun
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Daengngern, Rathawat
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Mori, Seiji
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Akutsu-Suyama, Kazuhiro
The electronic properties and excited-state intramolecular double proton transfer of 2,5-bis(2-benzimidazolyl)hydroquinone (bis-HBI) in a nonpolar solvent were investigated using a combined experimental and theoretical approach. Bis-HBI was successfully synthesized and its characterization was confirmed through 1H NMR and FT-IR. Three distinct emission peaks of bis-HBI were observed at 484, 597, and 730 nm, which were theoretically assigned to the di-enol (EE), mono-keto (EK), and di-keto (KK) species, respectively. The emission peaks at longer wavelengths (597 and 730 nm) are attributed to tautomerization upon photoexcitation and are assigned to the mono-keto and di-keto species, which result from multiple proton transfers. These species exhibit kinetically and thermodynamically favorable behaviors. On-the-fly dynamics simulations reveal that the double proton transfer process occurs ultrafast, within 433 fs. Additionally, both backward and forward proton transfers are observed during the first and second proton transfers, indicating tautomeric equilibria between the three species—EE, EK, and KK—on the excited-state surface. This is consistent with the potential energy surface along the proton transfer coordinate.
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A theoretical investigation into the demethylation mechanism of dimethylsulfide over the W3O6 cluster
(2025-07-01)
Aziz, Hafiz Aji
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Kungwan, Nawee
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Gleeson, Duangkamol
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Saelee, Tinnakorn
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Daengngern, Rathawat
Understanding how dimethyl sulfide (DMS) breaks down to form value-added products such as methanol on transition metal oxide catalysts is important for improving desulfurization processes. In this study, the reaction mechanism over a tungsten oxide cluster (W₃O₆) is elucidated using density functional theory (DFT) at the M06-L/LANL2DZ/aug-cc-pVTZ level of theory. Two competing mechanistic pathways were discovered over the W₃O₆ cluster: Pathway A) direct demethylation followed by methanol desorption and Pathway B) a water-assisted concerted demethylation pathway. Pathway A involves sequential steps with a moderate demethylation barrier (49.43 kcal/mol), but a significantly higher barrier (68.78 kcal/mol) for subsequent methanol formation, imposing a kinetic bottleneck. Remarkably, Pathway B, mediated by an explicit water molecule, facilitates a lower-barrier concerted transformation (56.19 kcal/mol), effectively bypassing the high-energy intermediate. Kinetic modeling via Transition State Theory and the Energetic Span Model reveal that despite the very low turnover frequency (TOF = 9.29 × 10−30 s⁻¹), the water-assisted pathway is energetically superior. These findings highlight the important role of water in helping the reaction proceed and offer insight for designing better catalysts for sulfur removal from DMS to methanol over the W₃O₆ cluster.

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