ABSTRACT
The thermoelectric (TE) performance of conducting polymers can be improved by the incorporation of carbon nanomaterials. In this work, the impact of carbon black (CB) on polypyrrole (PPy) and polypyrrole/polyaniline (PPy/PANI) binary composite have been investigated. Herein, PPy/PANI binary composite was initially prepared through chemical oxidative polymerization and then solution mixed with CB to form PPy/PANI/CB ternary nanocomposite. The structural and morphological analyses confirmed the formation of composites, and the strong interaction present between polymer matrix and CB. This was further confirmed by theoretical study, which showed strong noncovalent interaction and high complex stability between the materials. The thermoelectric results showed that both the electrical conductivity (σ) and Seebeck coefficient (S) has been increased with the increase in CB content (from 10 wt% to 30 wt%) and temperature (303 K to 373 K), while the thermal conductivity (κ) increase was low. The ternary nanocomposite involving 30 wt% of CB was found to be the most promising material which showed an enhanced power factor (PF) of 0.0251 µW/mK2 and high figure of merit (ZT) of 4.37x10-5 at 370 K. The enhancement in ZT for PPy/PANI/CB ternary composite is 2 times, 316 times, 17.3 times, 3.97 times, 11.7 times, and 6.8 times greater than other samples. The enhancement in power factor and ZT was due to energy filtering effect and strong non-covalent interactions between the homopolymers and CB.
ABSTRACT
A combined theoretical and experimental study of the dissociation of the di- and trication of the CH3Cl molecule has been performed. Experimentally, these multi-charged ions were produced after interactions of a CH3Cl effusive jet with a mono-energetic beam of H+ or Ar9+ projectile ions. Theoretically, we mapped the multi-dimensional potential energy surfaces of CH3Cl2+, H2CClH2+ and CH3Cl3+ species in their electronic ground and electronically excited states using post-Hartree-Fock configuration interaction methods. In addition to the obvious bond-breaking ionic fragments (i.e. H+ + CH2Cl+, H+ + CH2Cl2+ and CH3+ + Cl+), the formation of H2+ (+CHCl+ or CHCl2+), H3+ (+CCl+) and HCl+ (+CH2+) was observed upon bond rearrangement after ion impact of CH3Cl. The interaction strength of the incident projectiles is found to affect the relative yields on the observed dissociation channels, however, it has no effect on the kinetic energy releases of the fragmentation pathways. For the observed dissociation channels, plausible formation mechanisms were proposed. These reaction pathways take place on the ground and/or electronic excited potential energy surfaces of the doubly and triply charged CH3Cl ions, where spin-orbit and vibronic couplings are in action. Moreover, this work suggests that the mechanisms undertaken may depend on the multiply charged ion preparation by valence or inner-shell single photon photoionization, fast ion beam impact or ultrafast intense laser ionization.
ABSTRACT
The attachment and dissociation of a proton from a water molecule and the proton transfers at solid-liquid interfaces play vital roles in numerous biological, chemical processes and for the development of sustainable functional materials for energy harvesting and conversion applications. Using first-principles computational methodologies, we investigated the protonated forms of polyhedral oligomeric silsesquioxane (POSS-H+) interacting with water clusters (Wn, where n = 1-6) as a model to quantify the proton conducting and localization ability at solid-liquid interfaces. Successive addition of explicit water molecules to POSS-H+ shows that the assistance of at least three water molecules is required to dissociate the proton from POSS with the formation of an Eigen cation (H9O4+), whereas the presence of a fourth water molecule highly favors the formation of a Zundel ion (H5O2+). Reaction pathway and energy barrier analysis reveal that the formation of the Eigen cation requires significantly higher energy than the Zundel features. This confirms that the Zundel ion is destabilized and promptly converts in to Eigen ion at this interface. Moreover, we identified a Grotthuss-type mechanism for the proton transfer through a water chain close to the interface, where symmetrical and unsymmetrical arrangements of water molecules around H+ of protonated POSS-H+ are involved in the conduction of proton through water wires where successive Eigen-to-Zundel and Zundel-to-Eigen transformations are observed in quick succession.
