3.7 Photophysical and electrochemical properties
In order to further gain some insights into the excellent performance of bi-heterostructured O/ZCS/P-3 cages, various electro-/photo-chemical characterizations are carried out as displayed in Fig. 8. The most accelerated charge migration kinetics in O/ZCS/P-3 is clearly reflected by the significantly increased photocurrent response as shown in Fig. 8a. Moreover, electrochemical impedance spectra (EIS) exhibit that ITO/O/ZCS/P-3 electrode possesses a smaller high-frequency semicircle compared with other three electrodes (Fig. 8b), indicating a lower electron-transport resistance in the O/ZCS/P-3 material that ensures the faster charge migration. On the other hand, steady-state photoluminescence (PL) quenching reveals the most inhibited recombination of light-excited electron-hole pairs in O/ZCS/P-3 (Fig. 8c). Furthermore, time-resolved photoluminescence (TRPL) spectroscopy is applied to investigate the charge carrier dynamics of the as-prepared semiconductors (Fig. 8d). The decay kinetics of O/ZCS/P-3 exhibits shorter average lifetime (1.62 ns) in comparison with those of ZCS (1.78 ns), ZCS/CoP (1.75 ns) and ZCS/ Co3O4 QDs (1.70 ns), which signifies the O/ZCS/P-3 can faster promote the separation of photo-induced charge carriers. These results verify the faster separation and migration of light-excited charges in O/ZCS/P-3, thus leading to the high-performance H2 evolution.