The charge transfer characteristics of BPA and c-BPA (loaded on the electrode) were also investigated using the PEC tests. Fig. 7a shows the photocurrent generation under UV irradiation, which is much higher with BPA than c-BPA. This is also consistent with the photocatalytic activities for hydrogen NMS-P715 and 4-CP degradation. In addition, the decay in the open circuit potential (OCP) of the BPA electrode, which was monitored immediately after turning off the UV light, is markedly slower than that of the c-BPA electrode. This implies a slower recombination rate in the BPA electrode (Fig. 7b). Such similarities between the photocatalytic activities (for H2 evolution and 4-CP degradation) and the PEC properties clearly indicate that the structural and morphological advantages of the BPA significantly enhance the charge-separation efficiency within the agglomerate unit and reduce the recombination rate by the interparticle charge transfer through the 1 0 1 facets. To further confirm the enhanced charge transfer rate in the BPA electrode, electrochemical impedance spectroscopy (EIS) measurements were carried out. As shown in Fig. 7c, the arc size of the BPA sample is significantly smaller than that of c-BPA or P25. The smaller arc size in an EIS Nyquist plot indicates the smaller charge-transfer resistance on the electrode interface . This also supports the more efficient charge transfer within the BPA electrode as compared with that of c-BPA or P25.