In this study we compared the electrochemical pressure-concentration-temperature (EPCT) method with the gaseous phase pressure-concentration-temperature (PCT) method and demonstrated the differences between the two. Experimentally, this was done by electrochemically charging/discharging the electrodes of four different metal hydride (MH) alloys. The results indicate that in the PCT curve is flatter with a smaller hysteresis and a higher storage capacity compared to the EPCT curve. Moreover, while the PCT curves (up to around one third of the hydrogen storage capacity) reside in between the charge and discharge EPCT curves, the rest of the PCT curves are below the EPCT curves. Finally, we demonstrated a new calibration method based on the inflection points observed in the EPCT isotherms of a physical mixture of more than one alloy. This turning point can be used to find a preset calibration point to determine the state-of-charge.

Electrochemical Open-Circuit Voltage and Pressure-Concentration-Temperature Isotherm Comparison for Metal Hydride Alloys

TiVMn and TiCrMn alloys are promising hydrogen storage materials for onboard application due to their high hydrogen absorption content. However, the traditional synthesis method of melting and continuous necessary heat treatment and activation process are energy- and time-consuming. There is rarely any report on kinetics improvement and nanoprocessing in TiVMn- and TiCrMn-based alloys. Here, through ball milling with carbon black as additive, we synthesized face-centered cubic (FCC) structure TiVMn- and TiCrMn-based nanoalloys with mean particle sizes of around a few to tens of μm and with the crystallite size just 10 to 13 nm. Differential scanning calorimetry (DSC) measurements under hydrogen atmosphere of the two obtained TiVMn and TiCrMn nanoalloys show much enhancement on the hydrogen absorption performance. The mechanism of the property improvement and the difference in the two samples were discussed from microstructure and morphology aspects. The study here demonstrates a new potential methodology for development of next-generation hydrogen absorption materials.

/pdf/synthesis-morphology-and-hydrogen-absorption-properties-of-4pimom3ejk.pdf

Synthesis, Morphology, and Hydrogen Absorption Properties of TiVMn and TiCrMn Nanoalloys with a FCC Structure.

The hydrogen storage alloy electrodes of the type Ti4Ni2Oy (y=0, 0.3 and 0.6) and Ti3.5Zr0.5Ni2Oy (y=0.15 and 0.3) were investigated by impedance spectroscopy for potential application as negative electrode in alkaline secondary nickel-metal hydride (MH) batteries. The phase Ti4Ni2O0.30 was found to be electrochemically more stable during the cycling. The addition of copper or nickel powder as current collector improved the electrochemical behavior of the electrodes. It was possible in this way to decrease the charge transfer resistance. These additions have a negligible influence on the stability of electrode material during cycling.

AC impedance behavior of the Ti4Ni2Oy and Ti3.5Zr0.5Ni2Oy type metal hydride electrodes

In this chapter different materials used for hydrogen storage have been discussed in detail.

Maria Beltowska-Brzezinska

Papers

Electrochemical behaviour of multicomponent ZrTiVMnCrNi alloys in alkaline solution