Desarrollo de electrodos y electrolitos para baterías sólidas de ión litio en lámina delgada obtenidos por sol-gel

Tesis doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Química Inorgánica. Fecha de lectura: 18-12-2015Esta tesis tiene embargado el acceso al texto completo hasta el 18-06-2017Este trabajo ha sido realizado en el marco del Proyecto de I+D del Ministerio de Ciencia e Innovación: “Development of new electrolyte and electrode materials for all-solid-state thin film lithium batteries through solution process”, Programa Nacional de Internacionalización de la I+D. Subprograma: FCCI 2009. Modalidad ACI-PLAN E (cooperación España- Japón en Nanotecnología y Nuevos Materiales). Referencia: PLE2009-0074

Nanostructured poly(hydroquinonyl-benzoquinonyl sulfide)/multiwalled carbon nanotube composite cathodes

Cost-effective, simple, and easily reproducible synthesis methods of polymers are of profound significance when it comes to extracting high battery performance metrics from polymeric redox-active materials. This work reports a procedure for the solvothermal synthesis of a poly(hydroquinonyl-benzoquinonyl sulfide) (PHBQS) polymer and the development of its nanostructured composites with multiwalled carbon nanotubes (MWCNTs). Polymers are tested as high-performance cathode materials for Li$^+$ and Mg$^{2+}$ batteries. In configurations, compared to neat PHBQS, the PHBQS@5%MWCNT cathode exhibits superior electrochemical performance with high active material utilization owing to improved ion/electron transport pathways. Galvanostatic characterization of the PHBQS@5%MWCNT cathode in lithium batteries exhibited peak capacity up to 358 mAh g$^{−1}$ at a current density of 50 mA g$^{−1}$ (C/8) and excellent rate performance with a discharge capacity of 236 mAh g$^{−1}$ maintained even at high current density of 10C. The galvanostatic characterization in Mg batteries reveals more sluggish kinetics with a stable capacity of 200 mAh g$^{−1}$ at 50 mA g$^{−1}$

High-surface-area organic matrix tris(aza)pentacene supported platinum nanostructures as selective electrocatalyst for hydrogen oxidation/evolution reaction and suppressive for oxygen reduction reaction

Developing a Pt-based electrocatalytic material able to selectively catalyze hydrogen oxidation (HOR) while supressing oxygen reduction (ORR) is beneficial for durability of the fuel cells. Namely, degradation of carbon supported Pt particles is dramatically influenced by the unwanted ORR enrolling at the anode due to the air penetration during start-up/shut-down events. We present an organic matrix tris(aza)pentacene (TAP), which belongs to π-functional materials with ladder-like conjugated nitrogen-containing units, as the support for Pt to form a “smart” fuel cell anode able to selectively catalyze HOR and to suppress ORR. “Switching-on/off” of the composite material activity is provided by reversible reduction/oxidation of the TAP in the low potential region which provokes TAP - HxTAP transition. Conductivity of the reduced HxTAP enables supported Pt particles to effectively run HOR. In contrast, restricted conductivity of oxidized TAP analogue leads to the substantial drop in the ORR activity with respect to benchmark Pt/C catalyst

Suppressing platinum electrocatalyst degradation via a high-surface-area organic matrix support

Degradation of carbon-supported Pt nanocatalysts in fuel cells and electrolyzers hinders widespread commercialization of these green technologies. Transition between oxidized and reduced states of Pt during fast potential spikes triggers significant Pt dissolution. Therefore, designing Pt-based catalysts able to withstand such conditions is of critical importance. We report here on a strategy to suppress Pt dissolution by using an organic matrix tris(aza)pentacene (TAP) as an alternative support material for Pt. The major benefit of TAP is its potential-dependent conductivity in aqueous media, which was directly evidenced by electrochemical impedance spectroscopy. At potentials below ∼0.45 V$_{RHE}$, TAP is protonated and its conductivity is improved, which enables supported Pt to run hydrogen reactions. At potentials corresponding to Pt oxidation/reduction (>∼0.45 V$_{RHE}$), TAP is deprotonated and its conductivity is restricted. Tunable conductivity of TAP enhanced the durability of the Pt/TAP with respect to Pt/C when these two materials were subjected to the same degradation protocol (0.1 M HClO$_4$ electrolyte, 3000 voltammetric scans, 1 V/s, 0.05−1.4 V$_{RHE}$). The exceptional stability of Pt/TAP composite on a nanoscale level was confirmed by identical location TEM imaging before and after the used degradation protocol. Suppression of transient Pt dissolution from Pt/TAP with respect to the Pt/C benchmark was directly measured in a setup consisting of an electrochemical flow cell connected to inductively coupled plasma-mass spectrometry