After reviewing relevant equations for the calculation of exchange current density, a new equation is derived for hydrogen electrode reactions to correct for the influences of the hydrogen concentration change in the vicinity to the electrode surface. This equation is able to describe the polarization curve shape in the small polarization region as well as to calculate the exchange current (density). The abilities of this equation are demonstrated by the data obtained with a Pt rotating disk electrode in 0.1 mol l−1 KOH solution. The exchange current density at 298 K under 1 atmosphere hydrogen pressure is found to be 0.103 mA cm−2 with an apparent activation energy of 33.5 kJ mol−1. At a constant temperature, the exchange current is found to be proportional to the square root of the hydrogen partial pressure in the solution.

This is the first report of a novel anode catalyst, Pt/Ti2O, and its use for the complete 8-electron oxidation of borohydride without hydrogen evolution in a potential region negative to reversible hydrogen electrode (RHE). A major obstacle to the development of direct borohydride fuel cells (DBFC) has been the hydrogen evolution at the negative electrode, which causes low coulombic efficiency and safety problems. Attempts to prevent hydrogen evolution during the oxidation of borohydride on a fuel cell anode have always resulted in a shift of the anode potential to values more positive than the RHE potential, thus losing the advantages of DBFC in comparison to conventional hydrogen fuel cells. Pt supported on conductive titanium oxides (Ti2O) has been found to catalyze the 8-electron oxidation of borohydride without hydrogen evolution in a potential range more negative than RHE, which is desired in order to have a DBFC that is practically applicable. Mechanism of the direct 8-electron oxidation process is discussed on the basis of a synergistic effect at the surface of Pt/Ti2O catalyst.

The potential transient during pulse discharge is studied for ultra-thin silver oxide electrodes with special attention to the potential valleys. The potential valley appears in different ways depending on the history of charge and discharge undergone by the electrode and is attributed to highly resistive Ag2O layers. The latter may exist on the surface of silver substrate (current collector) or inside the particles of active material. Moreover, the resistive Ag2O layer may be partially reduced during current pulses and partially restored during pulse intervals, leading to complicated potential responses to the pulse discharge. To prevent the annoying potential valley, the silver electrode is suggested to be charged to an extent below the full conversion of Ag to Ag2O.

Ultra-thin silver electrodes for high power density pulse batteries are prepared by anodic oxidation and cathodic reduction of thin silver foils in 0.1 mol/l HCl aqueous solution. The active layer thus formed has a porosity about 65%. The thickness of the active layer can be controlled by the charge passed in oxidation. Typically, silver foils 50 μm thick are used as the raw material and finished in 80 μm electrodes with nominal capacity 14 C/cm2 on each side. These electrodes can be charged and discharged at very high rates (typically 10C charge and 102C discharge) with about 90% utilization of the active material. Potential valleys, most possibly due to the resistive Ag2O, are observed on both steady-state and pulse discharges. To prevent the potential valleys, which are most annoying to pulse applications, charging is suggested to be confined within the low potential plateau region.

With the integrating sphere device, in situ UV–Vis diffuse reflectance spectra were obtained for the deintercalation process of a lithiated petroleum coke electrode. In the lowest frequency region studied the reflectance was found to increase with increasing lithium content, whereas little change was seen in the π–π* transition region. According to a simplified simulation, the spectral changes are thought to be associated mainly with the change of the number of free charge carrier electrons.