The addition–elimination (A–E) mechanism proposed for the oxidation of methanol to formaldehyde by PQQ-containing methanol dehydrogenase (MDH) enzyme is investigated at the Becke–Lee–Yang–Parr/double numerical with polarisation density functional theory level with the DMol³ module of the Materials Studio^® software. Two different models representing the Methylobacterium extorquens MDH (1H4I) active site are considered and tested upon methanol oxidation in gas phase. Model A consists of the PQQ molecule, the Ca^2 +  ion and aspartic acid (ASP-303), and model B contains also glutamic acid (GLU-177) and asparagine (ASN-261) in addition to the contents of model A. The first proton transfer from methanol to ASP-303 and from ASP-303 to PQQ is affected by the model size; however, the second proton transfer corresponding to the cleavage of C_met–H17 is practically unaffected by the MDH active site model under consideration. The energy barrier for the cleavage of the C atom of methanol (C_met) and H17 is 13 and 17 kcal/mol for models A and B, respectively, in good agreement with the general kinetic requirements of an enzymatic process. Step 1 as proposed in the literature is not kinetically favourable in the gas phase at this theory level. It is possible then, that either solvent effects are critical or that one or more intermediate steps leading to the formation of the first intermediate complex are missing from the proposed methanol A–E mechanism for the oxidation of methanol by MDH.

Using impedance spectroscopy the electrical response of sensors with various porous Y-stabilized ZrO₂ (YSZ) microstructures was measured for gas concentrations containing 0–100 ppm NO with 10.5%O₂ at temperatures ranging from 600–700 °C. The impedance response increased substantially as the sensor porosity increased from 46%–50%. Activation energies calculated based on data from the impedance measurements increased in magnitude (97.4–104.9 kJ/mol for 100 ppm NO) with respect to increasing YSZ porosity. Analysis of the oxygen partial pressure dependence of the sensors suggested that dissociative adsorption was the dominant rate limiting. The PWC/DNP theory level was used to investigate the gas-phase energy barrier of the 2NO+O₂→2NO₂ reaction on a 56-atom YSZ/Au model cluster using Density Functional Theory and Linear Synchronous Transit/Quadratic Synchronous Transit calculations. The reaction path shows oxygen surface reactions that begin with NO association with adsorbed O₂ on a Zr surface site, followed by O₂ dissociative adsorption, atomic oxygen diffusion, and further NO₂ formation. The free energy barrier was calculated to be 181.7 kJ/mol at PWC/DNP. A qualitative comparison with the extrapolated data at 62% ± 2% porosity representing the YSZ model cluster indicates that the calculated barriers are in reasonable agreement with experiments, especially when the RPBE functional is used.

Structure and stability of pristine and modified NaAlH₄ are first investigated using density functional theory (DFT) with plane-wave basis and PW91 functional. Vacancy and Ti-dopant effects in the sodium alanate bulk, (0 0 1) surface, and on-top (0 0 1) surface are then studied considering Na and interstitial lattice sites. Calculated substitution energies of Ti-doped (0 0 1) NaAlH₄ surfaces have shown almost equal probability of substitution at both lattice and interstitial sites. Ti–Al–H complexes are formed depending on the accessible AlH₄ groups around the Ti dopant. TiAl₂H₇ and TiAl₂H₂ complexes are found after geometry optimising doped-NaAlH₄ surface models. Their stability and dynamics over time at 423 and 448 K are investigated using periodic density functional molecular dynamics (DFT-MD) simulations. Results have shown increased association of Al and H with the complexes as time evolves. DFT-MD simulations show evolution from TiAl₂H₇ to TiAl₅H₇ as time and temperature increase in case of Ti dopant at Na surface site (Ti → S_Na), and evolution from TiAl₂H₂ to TiAl₃H₆ at 423 K and TiAl₃H₇ at 448 K in case of Ti dopant on-top of the interstitial surface site (Ti → T_I) with time.

The environmental performance of chitosan production is evaluated through a rigorous computational comparison between traditional thermochemical deacetylation and innovative green synthesis pathways utilizing Deep Eutectic Solvents (DES). Implementation of the Waste Reduction (WAR) algorithm facilitates the quantification of the Potential Environmental Impact (PEI) across eight toxicological and ecotoxicological categories, providing a systematic benchmark for process sustainability. While the conventional route, characterized by the intensive consumption of HCl and NaOH, generates a substantial environmental burden of 1.37 × 10⁷ PEI/ton, the optimized green architecture leveraging a choline chloride:ethylene glycol (ChCl:EG) system achieves a radical reduction to 2.25 × 10⁴ PEI/ton. This 99.8% decrease in PEI is primarily driven by the mitigation of Human Toxicity Potential (HTP) and Acidification Potential (AP) through the substitution of corrosive mineral acids and volatile organics with biodegradable, low-vapor-pressure alternatives. These findings substantiate the integration of DES-mediated biorefineries as a high-efficiency strategy for the valorization of marine waste into high-purity biopolymers, aligning with the requirements for industrial process intensification and circular bioeconomy standards.