Pressure Induced Topochemical Polymerizationof Solid Acryalmide Facilitated by Anisotropic Response of Hydrogen Bond Network

The pressure induced polymerization of molecular solids is an appealing route to obtain pure, crystalline polymers without the need for radical initiators. Here, we report a detailed density functional theory (DFT) based study of the structural and chemical changes that occur in defect free solid acrylamide, a hydrogen bonded crystal, when it is subjected to hydrostatic pressures. Our calculations predict a polymerization pressure of 94 GPa, in contrast to experimental estimates of 17 GPa, while being able to reproduce the experimentally measured pressure dependent spectroscopic features. Interestingly, we find that the two-dimensional hydrogen bond network templates a topochemical polymerization by aligning the atoms through an anisotropic response at low pressures. This results not only in conventional C-C, but also unusual C-O polymeric linkages, as well as a new hydrogen bonded framework, with both NH... O and C-H...O bonds.</p

Enhanced Pseudocapacitance of MoO₃‑Reduced Graphene Oxide Hybrids with Insight from Density Functional Theory Investigations

Hydrothermally obtained MoO₃/reduced graphene oxide (RGO) hybrid registered a specific capacitance of 724 F g^‑1 at 1 A g^‑1, superior to the supercapacitor performance obtained from similar hybrid structures. Density functional theory (DFT) simulations further corroborated our claim in terms of both enhanced quantum capacitance and relevant insight from the electronic density of states (DOS) for MoO₃/RGO. Maximum capacitance is achieved for 12 wt % of RGO and then it reduces as observed in the experiment. The appearance of additional density of states from the C p_<i>z</i> orbital in the band gap region near the Fermi level on introduction of RGO in MoO₃ is responsible for the enhanced capacitance in MoO₃/RGO

Urea-Assisted Room Temperature Stabilized Metastable β‑NiMoO₄: Experimental and Theoretical Insights into its Unique Bifunctional Activity toward Oxygen Evolution and Supercapacitor

Room-temperature stabilization of metastable β-NiMoO₄ is achieved through urea-assisted hydrothermal synthesis technique. Structural and morphological studies provided significant insights for the metastable phase. Furthermore, detailed electrochemical investigations showcased its activity toward energy storage and conversion, yielding intriguing results. Comparison with the stable polymorph, α-NiMoO₄, has also been borne out to support the enhanced electrochemical activities of the as-obtained β-NiMoO₄. A specific capacitance of ∼4188 F g^–1 (at a current density of 5 A g^–1) has been observed showing its exceptional faradic capacitance. We qualitatively and extensively demonstrate through the analysis of density of states (DOS) obtained from first-principles calculations that, enhanced DOS near top of the valence band and empty 4d orbital of Mo near Fermi level make β-NiMoO₄ better energy storage and conversion material compared to α-NiMoO₄. Likewise, from the oxygen evolution reaction experiment, it is found that the state of art current density of 10 mA cm^–2 is achieved at overpotential of 300 mV, which is much lower than that of IrO₂/C. First-principles calculations also confirm a lower overpotential of 350 mV for β-NiMoO<sub>4.</sub