Atomic layer deposition of Pt@CsH_2PO_4 for the cathodes of solid acid fuel cells

Atomic layer deposition (ALD) has been used to apply continuous Pt films on powders of the solid acid CsH_2PO_4 (CDP), in turn, used in the preparation of cathodes in solid acid fuel cells (SAFCs). The film deposition was carried out at 150 °C using trimethyl(methylcyclopentadienyl)platinum (MeCpPtMe_3) as the Pt source and ozone as the reactant for ligand removal. Chemical analysis showed a Pt growth rate of 0.09 ± 0.01 wt%/cycle subsequent to an initial nucleation delay of 84 ± 20 cycles. Electron microscopy revealed the contiguous nature of the films prepared using 200 or more cycles. The cathode overpotential (0.48 ± 0.02 V at a current density of 200 mA/cm^2) was independent of Pt deposition amount beyond the minimum required to achieve these continuous films. The cell electrochemical characteristics were moreover extremely stable with time, with the cathode overpotentials increasing by no more than 10 mV over a 100 h period of measurement. Thus, ALD holds promise as an effective tool in the preparation of SAFC cathodes with high activity and excellent stability

Atomic layer deposition of Pt@CsH_2PO_4 for the cathodes of solid acid fuel cells

Atomic layer deposition (ALD) has been used to apply continuous Pt films on powders of the solid acid CsH_2PO_4 (CDP), in turn, used in the preparation of cathodes in solid acid fuel cells (SAFCs). The film deposition was carried out at 150 °C using trimethyl(methylcyclopentadienyl)platinum (MeCpPtMe_3) as the Pt source and ozone as the reactant for ligand removal. Chemical analysis showed a Pt growth rate of 0.09 ± 0.01 wt%/cycle subsequent to an initial nucleation delay of 84 ± 20 cycles. Electron microscopy revealed the contiguous nature of the films prepared using 200 or more cycles. The cathode overpotential (0.48 ± 0.02 V at a current density of 200 mA/cm^2) was independent of Pt deposition amount beyond the minimum required to achieve these continuous films. The cell electrochemical characteristics were moreover extremely stable with time, with the cathode overpotentials increasing by no more than 10 mV over a 100 h period of measurement. Thus, ALD holds promise as an effective tool in the preparation of SAFC cathodes with high activity and excellent stability

Partially reduced graphene oxide-gold nanorods composite based bioelectrode of improved sensing performance

The present work proposes partially reduced graphene oxide-gold nanorods supported by chitosan (CH-prGO-AuNRs) as a potential bioelectrode material for enhanced glucose sensing. Developed on ITO substrate by immobilizing glucose oxidase on CH-prGO-AuNRs composite, these CH-prGO-AuNRs/ITO bioelectrodes demonstrate high sensitivity of 3.2 mu A/(mg/dL)/cm(2) and linear range of 25-200 mg/dL with an ability to detect as low as 14.5 mg/dL. Further, these CH-prGO-AuNRs/ITO based electrodes attest synergistiacally enhanced sensing properties when compared to simple graphene oxide based CH-GO/ITO electrode. This is evident from one order higher electron transfer rate constant (K-s) value in case of CH-prGO-AuNRs modified electrode (12.4 x 10(-2) cm/s), in contrast to CH-GO/ITO electrode (6 x 10(-3) cm/s). Additionally, very low K-m value [15.4 mg/dL(0.85 mM)] ensures better binding affinity of enzyme to substrate which is desirable for good biosensor stability and resistance to environmental interferences. Hence, with better loading capacity, kinetics and stability, the proposed CH-prGO-AuNRs composite shows tremendous potential to detect several bio-analytes in the coming future

Elucidating the Reaction Pathway in the Ammonolysis of MoO₃ via In Situ Powder X‑ray Diffraction and Transmission Electron Microscopy

Molybdenum nitrides and oxynitrides are of interest as catalysts for a wide variety of applications. They are commonly synthesized via the high-temperature ammonolysis of MoO3 in which the oxide precursor is reacted with gas-phase ammonia at an elevated temperature. Despite the widespread adoption of ammonolysis as a synthetic approach, the reaction pathway leading to the formation of molybdenum nitrides by this method remains poorly understood. In this work, combined in situ powder X-ray diffraction (PXRD) and in situ transmission electron microscopy (TEM) are used to fully map the transformation of MoO3 to the final product and identify the structure relationships among the precursors, intermediates, and product. Two key intermediates, MoO2 and HxMoO3-I (x ≈ 0.3), are identified, with hexagonal δ-MoN occurring as a minor, short-lived, high-temperature intermediate, depending on reaction conditions. Notably, the reaction is topotactic throughout the transformation from MoO3 to HxMoO3-I to MoO2 and finally to cubic γ-MoOxNy. There is no evidence for direct transformation from HxMoO3-I to γ-MoOxNy, a route suggested in the prior literature. Moreover, even when the reaction follows a pathway in which the material fully transforms to MoO2 at intermediate temperatures, single-phase γ-MoOxNy is obtained after reaction at 800 °C. This comprehensive elucidation of the reaction pathway provides a roadmap for future tuning of the molybdenum oxynitride morphology and chemistry