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Influence of Ordered Mesoporous Oxides in Plasma-Assisted Ammonia Synthesis
Widespread implementation of dielectric barrier discharge (DBD)-assisted NH 3 synthesis, a nascent technology operating under sustainable, ambient conditions, is hindered by low energy yields due to, in part, poor fundamental understanding. Porous oxides used to support metal nanoparticle catalysts have shown significant energy yield contributions for DBD-assisted NH 3 synthesis even without metal. Using an AC-powered, coaxial, single-stage reactor at 16 kV with equimolar (N 2 /H 2 ) feed, we measured NH 3 synthesis rates in the presence of different nonordered oxides, ordered SiO 2 structures (SBA-15 and MCM-41), and ordered Al-incorporated analogues (γ-Al 2 O 3 -coated with varying Al-loadings and Al-substitution, respectively: Al 2 O 3 -SBA-15 and Al-MCM-41). We systematically quantified NH 3 energy yield dependence on pore structures and material identities (i.e., ordered pores and Al incorporation) known to facilitate higher DBD-assisted NH 3 synthesis rates. SBA-15 displayed a higher steady-state energy yield than MCM-41, indicating that framework type is a crucial factor, with both ordered porous systems outperforming fumed SiO 2 . 10 wt % Al maximized in situ NH 3 uptake among the various Al loadings, exhibiting a higher steady-state energy yield and similar power to SBA-15. However, Al-MCM-41 had a similar steady-state energy yield and lower power than MCM-41, likely due to the extended γ-Al 2 O 3 surface that has a dielectric constant higher than that of SiO 2 . Both Al-incorporated analogues benefit from surface acid sites that can adsorb NH 3 in situ, resulting in higher overall NH 3 energy yields than that of their parent ordered SiO 2 . Al 2 O 3 -SBA-15 shielded more NH 3 than Al-MCM-41, likely due to a higher acid site density than the acid site identity. Furthermore, Al incorporation via γ-Al 2 O 3 coating more successfully improves the NH 3 energy yield; together with the high-performing ordered framework, these analogues are potential metal catalyst supports with promising energy yields for DBD-assisted synthesis of NH 3 and other chemicals.
First-Principles Microkinetic Model for Ammonia Synthesis on Fe(110) under Nonequilibrium Programmable Heating and Quenching Operation
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Plasma-Assisted Surface Nitridation of Proton Intercalatable WO 3 for Efficient Electrocatalytic Ammonia Synthesis
Electrocatalytic nitrogen reduction (eNRR) offers a green pathway for the production of NH 3 from N 2 and H 2 O under ambient conditions. Transition metal oxynitrides (TMO x N y ) are among the most promising catalysts but face challenges in achieving a high yield and faradaic efficiency (FE). This work develops a hybrid WO x N y /WO 3 catalyst with a unique heterogeneous interfacial complexion (HIC) structure. This design enables in situ generation and delivery of highly active hydrogen atoms (H*) in acidic electrolytes, promoting nitrogen hydrogenation and the formation of nitrogen vacancies (Nv) on the WO x N y surface. This significantly enhances the selectivity of eNRR for NH 3 synthesis while suppressing the hydrogen evolution reaction (HER). A simple two-step fabrication process─microwave hydrothermal growth followed by plasma-assisted surface nitridation─was developed to fabricate the designed catalyst electrode, achieving an NH 3 yield of 3.2 × 10 –10 mol·cm –2 ·s –1 with 40.1% FE, outperforming most TMN/TMO x N y electrocatalysts. Multiple control experiments confirm that the eNRR follows an HIC-enhanced Mars–van Krevelen (MvK) mechanism.
A Flexible Phosphonate Metal–Organic Framework for Enhanced Cooperative Ammonia Capture
Not provided.
Selective Stepwise Reduction of Nitrate and Nitrite to Dinitrogen or Ammonia
Not Available
Heterobimetallic Iridium-Niobia Catalyst for Efficient and Selective Methane Ammonia Reforming
A Surface OrganoMetallic Chemistry (SOMC) approach, leveraging a molecularly defined heterobimetallic niobium–iridium complex, was used to prepare a mesoporous SBA-15 silica-supported Ir-NbOx catalyst. The resulting Ir-NbOx/SiO2 catalyst exhibited excellent catalytic performance in selective methane/ammonia reforming. Specifically, the Ir-NbOx/SiO2 catalyst showed significantly higher activity (turnover frequency 8.5 s–1), selectivity (75%), and stability than the Ir/SiO2 analog, whereas the NbOx/SiO2 counterpart was almost inactive. This contrasts with ethane/ammonia reforming via C–C cleavage, for which the bimetallic Ir-NbOx/SiO2 was less active than Ir/SiO2, demonstrating tuned selectivity toward C–H activation rather than C–C cleavage due to the Ir/NbOx synergy. Importantly, an Ir-NbOx/SiO2 reference catalyst, prepared by conventional impregnation/calcination/reduction steps, was found to be inactive, highlighting the value of the SOMC catalyst preparation approach using well-defined heterobimetallic precursors. These results represent a significant advance over existing catalysts due to the atomic-scale synergy between Ir and NbOx sites, enabling access to activity and selectivity regimes inaccessible to monometallic analogs.
Molecular beam scattering of ammonia from a dodecane flat liquid jet
The evaporation and scattering of ND 3 from a dodecane flat liquid jet are investigated and the results are compared with previous studies on molecular beam scattering from liquid surfaces. Evaporation is well-described by a Maxwell–Boltzmann flux distribution with a cos θ angular distribution at the liquid temperature. Scattering experiments at E i = 28.8 kJ mol -1 over a range of deflection angles show evidence for impulsive scattering and thermal desorption. Further, at a deflection angle of 90°, the thermal desorption fraction is 0.49, which is higher than that of other molecules previously scattered from dodecane and consistent with work performed on NH 3 scattering from a squalane-wetted wheel. ND 3 scattering from dodecane results in super-specular scattering, as seen in previous experiments on dodecane. The impulsive scattering channel is fitted to a “soft-sphere” model, yielding an effective surface mass of 55 amu and an internal excitation of 5.08 kJ mol -1 . Overall, impulsively scattered ND 3 behaves similarly to other small molecules scattered from dodecane.
Single-atom vs. single-superatom as catalysts for ammonia production
A new class of single-superatom catalyst (TiO, ZrO, and WC) supported on graphene is shown to outperform the stability and activity of their corresponding single-atom catalysts (Ni, Pd and Pt) for the electrochemical nitrogen reduction reaction.
Ammonia-free synthesis of lithium manganese iron phosphate cathodes via a co-precipitation reaction
A novel precursor phase (Mn, Fe) 5 (PO 4 ) 2 (HPO 4 ) 2 ·4H 2 O is introduced with a co-precipitation reaction, enabling a low-cost, sustainable, scalable production of LMFP cathodes exhibiting excellent cycling stability with good tap density.
Electrochemical reduction of ammonia-captured CO 2 to CO over a nickel single-atom catalyst
Carbon reactive capture and conversion offers a sustainable route to valuable chemicals and fuels while aiding Green House Gas (GHG) reduction. Direct electrochemical conversion of capture solutions like bicarbonate avoids the energy demands of conventional CO 2 regeneration. Ammonium bicarbonate (NH 4 HCO 3 ) is particularly attractive due to its low decomposition temperature and ability to supply in situ CO 2 from dilute sources without requiring purified CO 2 . Meanwhile, single-atom catalysts (SACs) with nitrogen-coordinated metal sites further enhance CO 2 reduction efficiency using Earth-abundant materials. In this study, we demonstrate a nickel single-atom catalyst (Ni-SAC)-based electrolyzer that utilizes NH 4 HCO 3 as the CO 2 source, achieving significantly improved CO production performance compared to the conventional silver cathodes used in the CO 2 reduction reaction (CO 2 RR) to produce CO. The Ni-SAC cathode exhibited a Faradaic efficiency of 60.1% for CO production at −200 mA cm −2 , while the silver cathode achieved a Faradaic efficiency of only 2%, likely due to ammonium-induced poisoning. Furthermore, the integration of a customized microporous layer onto the electrode significantly increased the Faradaic efficiency from 64% to 83% at −100 mA cm −2 , emphasizing the crucial role of electrode structure optimization in enhancing CO selectivity. These findings demonstrate a sustainable and economically viable strategy for green CO production directly from CO 2 capture solutions.
In-situ species concentration measurements in ammonia mix flames using FTIR spectroscopy
Presentation at the 2024 ASME Turbo Expo detailing in-situ NO, NH3, H2O, and temperature measurements in CH4/NH3 and H2/NH3 flames using FTIR spectroscopy.
Recovery of valuable metals from electronic waste using a novel ammonia-based hydrometallurgical process
The growing quantity of waste electrical and electronic equipment (WEEE), also known as electronic waste (E-waste), has been an area of growing public concern. The abundance of valuable metals contained in waste printed circuit boards (WPCBs) has made it a promising secondary resource, especially for Cu and Au. Although the recovery of metals from WPCBs via hydrometallurgical routes has been studied extensively over the past 20 years, most of the research has been limited in the laboratory. In current hydrometallurgical processes, strong acids and expensive oxidizers are often used to ensure a high recovery of metals without considering the sustainability aspects of the environment and economics. To improve upon current hydrometallurgical offerings, the current study seeks to develop an energy-saving, environmentally friendly, economic and sustainable process to efficiently recover the valuable metals from real-world end-of-life WPCBs. The new contributions presented in this study are 1) design and evaluation of a comprehensive hydrometallurgical flowsheet; 2) employment of real end-of-life PCBs as feed materials in an investigation on Cu-NH3 leaching kinetics; 3) further application of kinetic model on a counter flow process simulation; and 4) evaluation of the influences by co-existing metals in Au-S2O3 leaching and recommendation for favorable leaching conditions.