Hydrogen discharge curves

Figure 7. Hydrogen discharge curves (1 SCFM) for Ergenics storage unit (90 SCF)...

Figure 12. Top Schematic model showing the mechanism of lithium storage in hydrogen containing carbons as proposed in Ref. [2471. Below Schematic charge/discharge curve of a hydrogen containing carbon.

Titanium disulfide, 25 57, 58 Titanium disulfide electrodes sloping discharge curve, 3 414 Titanium esters, 25 1 Titanium fluorides, 25 47-49 Titanium halides, 25 47-55 Titanium hydride, 13 626 Titanium hydrides, 25 5 Titanium-hydrogen system, 25 3-5 phase diagram for, 25 5 Titanium iodides, 25 54-55 Titanium/isopropoxy/nitrilotriethoxy ratio, 25 93... 

Predictions based on the volcano curve do not show any general validity since only a few combinations give more active materials. In particular, it is to be noted that Ni, Co and Fe appear on the right branch of the volcano curve if the A//ad measured in the gas phase is used [54], Thus, they would be on the same branch as Mo. They appear on the left branch of the curve [66] if the heat of adsorption is derived in situ from electrochemical measurements [80]. This indicates that these metals are modified by hydrogen discharge, probably because of hydrogen absorption which renders the surface adsorption bond weaker. The same possibility has been pointed out for Pt [81]. Thus, the verification of the prediction based on the volcano curve does not appear to be entirely convincent. 

Figure 10-12. Energy cost of the plasma-chemical pyrolysis of methane as a function of the specific plasma energy input upper curve, total energy cost of the process with respect to the total produced hydrogen lower curve, electrical energy cost with respect to additional hydrogen produced by the discharge.

Electrochemical cell with quartz window and saturated calomel electrode as a reference electrode was used (Fig. 3). Photoelectrochemical measurements were conducted with Pl-50-1 potentiostat under illumination power density of 75 mW/cm. At first the efficiency of energy accumulation (in the form of absorbed hydrogen) was estimated from the cathode discharge curves and from the hydrogen volume released under cathode heating. The volume of hydrogen released was measured in the tailor-made setup. The discharge capacity measurements were performed in electrochemical cell with nickel counter electrode. 

Figure 29.2. Charging-discharge curves for HSC at / = lOmA/cm. (1) Voltage U on HSC terminals (2) and (3) potentials of the positive and negative electrodes versus the hydrogen electrode in the same solution.

Fig. 9. Charge-discharge curves for medium-temperature hydrogen-oxygen storage devices.

II turns into case I. Consequently, this could be an explanation for the experimental increase in the steady-state Tafel slope v/iih decreasing pH. The second set of experimental data corresponds to case III, that is, a very high standard rate of Volmer-Heyrovsky cathodic hydrogen discharge in comparison with the rates of oxidation of atomic hydrogen and of physical desorption of molecular hydrogen, at kinks. Theoretical polarization curves computed on the basis of kinetic formulas describing cases II and... 

From a careful analysis of Eqs. (81) and (82)in conjunction with (71), one can notice that there is no other possible correlation between the terms of these equations leading to low Tafel slopes. Thus, if according to the inequalities in Eq. (86) the contribution of the hydrogen discharge to the total current is negligible in the linear region of the polarization curve, the predominance of any other term, except Ci ty /Ai in the denominator, yields Tafel slopes between 120 and o. Concomitantly, the coverage by bare metal atoms drastically decreases. 

---