The decrease of oxygen evolution current is attributed to the decrease in electrode area and to the loss in the electrochemical activity.
If we exclude the decrease of porosity, this evolution could be explained by the increasing contribution of some phases with lower refractive index upon annealing (like SiO2 (1.46)) [8]. Figure 2a represents the evolution of the FTIR spectra as a function of TA.
In our study, the decrease of the photosynthetic O2 evolution rate under heat stress was associated with electron transport capacity, which showed that the PSII of the photosynthetic apparatus was damaged.
Based on these loadings, the significant observations are: a small residual strain, the decrease of transformation yield stresses and the evolution of the hysteresis size with the number of cycles.
Now, a decrease of H2 evolution has been found proportional to the coverage of metal adatoms.
Chlamydomonas reinhardtii has shown a 75% decrease of oxygen evolution in cells being starved from P after 4 days, and a similar decrease in oxygen evolution after 1 day of S deprivation (Wykoff et al., 1998).
However, in a truly symmetrical case the increase in the rate of evolution in the fast-evolving copy will be of the same magnitude as the decrease in the rate of evolution of the slow copy.
At ca. −1.45 V, i.e. just before the hydrogen evolution reaction, the abrupt decrease of the cathodic current is due to the electrode poisoning by adsorbed hydrogen.
The early burst model (Blomberg et al., 2003; Freckleton and Harvey, 2006) offers an alternative that decreases the rate of evolution exponentially through time, and describes a process of adaptive radiation [ Harmon et al. (2010) provide a detailed comparison].
Irradiation of the solution under a high concentration of O2 in the headspace presumably also resulted in the formation of increased amounts of singlet O2, causing the decreased lifetime of the photo-H2 evolution system.
