Heterometallic Metal-Organic Frameworks for Enhanced Hydrogen Generation from Syngas: A Density Functional Theory Approach.

Although methane poses environmental concerns, it is employed in hydrogen production processes such as steam-methane reforming (SMR), which has an issue of by-products released. Initiatives are being pursued to address CO and CO2 emissions using carbon capture methods, with the goal of minimizing environmental harm while improving pure hydrogen generation from syngas. In this study, porous coordination network (PCN-250) has been studied for its selective adsorption property towards CO, CO2 and H2O as syngas mixture to obtain pure hydrogen. For this purpose, the trimetallic cluster node Fe2M (where Fe2 represents the 3+ oxidation state and M is Cr(II), Mn(II), Fe(II), Co(II), Ni(II), and Zn(II)) has been considered. Fe(III) in combination with metal atoms like Cr(II), Co(II), or Ni(II) has been found to exhibit enhanced adsorption properties towards CO, CO2 and H2O. The molecule with the strongest interaction was found to be H2O over Fe(III)2Zn(II) cluster and weakest interaction was found between H2 and Fe(III)2Ni(II). Charge transfer, natural bond orbital (NBO) and spin density analyses reveal the electronic structural properties of this combination, leading to enhanced adsorption of CO and CO2.

Active Site Engineering and Theoretical Aspects of "Superhydrophilic" Nanostructure Array Enabling Efficient Overall Water Electrolysis.

The rational design of noble metal-free electrocatalysts holds great promise for cost-effective green hydrogen generation through water electrolysis. In this context, here, the development of a superhydrophilic bifunctional electrocatalyst that facilitates both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in alkaline conditions is demonstrated. This is achieved through the in situ growth of hierarchical NiMoO4 @CoMoO4 ·xH2 O nanostructure on nickel foam (NF) via a two-step hydrothermal synthesis method. NiMoO4 @CoMoO4 ·xH2 O/NF facilitates OER and HER at the overpotentials of 180 and 220 mV, respectively, at the current density of 10 mA cm-2 . The NiMoO4 @CoMoO4 ·xH2 O/NF ǁ NiMoO4 @CoMoO4 ·xH2 O/NF cell can be operated at a potential of 1.60 V compared to 1.63 V displayed by the system based on the Pt/C@NFǁRuO2 @NF standard electrode pair configuration at 10 mA cm-2 for overall water splitting. The density functional theory calculations for the OER process elucidate that the lowest ΔG of NiMoO4 @CoMoO4 compared to both Ni and NiMoO4 is due to the presence of Co in the OER catalytic site and its synergistic interaction with NiMoO4 . The preparative strategy and mechanistic understanding make the windows open for the large-scale production of the robust and less expensive electrode material for the overall water electrolysis.

Mapping the Finite-Temperature Behavior of Conformations to Their Potential Energy Barriers: Case Studies on Si6B and Si5B Clusters.

Dynamical simulations of molecules and materials have been the route to understand the rearrangement of atoms within them at different temperatures. Born-Oppenheimer molecular dynamical simulations have further helped to comprehend the reaction dynamics at various finite temperatures. We take a case study of Si6B and Si5B clusters and demonstrate that their finite-temperature behavior is rather mapped to the potential energy surface. The study further brings forth the fact that an accurate description of the dynamics is rather coupled with the accuracy of the method in defining the potential energy surface. A more precise potential energy surface generated through the coupled cluster method is finally used to identify the most accurate description of the potential energy surface and the interconnected finite-temperature behavior.