Fig. 1. Charge-transfer route in type-II heterojunction and its inadequacies. (A) type-II heterojunction. (B) like charges repel and opposite charges attract due to columbic force. PC I and PC II stand for photocatalyst I and photocatalyst II, respectively. Figures taken from Ref. [1].

Fig. 2. Problems faced by charge transfer route in traditional and all-solid-state Z-scheme heterojunctions. (A) original proposed and (B) thermodynamically favored charge-transfer mode in traditional Z-scheme photocatalysts. (C) original proposed and (D) thermodynamically favored charge-transfer mode in all-solid-state Z-scheme photocatalysts. Figures taken from Ref. [1].

Fig. 2. Problems faced by charge transfer route in traditional and all-solid-state Z-scheme heterojunctions. (A) original proposed and (B) thermodynamically favored charge-transfer mode in traditional Z-scheme photocatalysts. (C) original proposed and (D) thermodynamically favored charge-transfer mode in all-solid-state Z-scheme photocatalysts. Figures taken from Ref. [1].

Fig. 3. Charge-transfer processes in an S-scheme heterojunction before contact (A), after contact (B), and photogenerated charge carrier transfer process under light irradiation (C). Figures taken from Ref. [1].

Fig. 3. Charge-transfer processes in an S-scheme heterojunction before contact (A), after contact (B), and photogenerated charge carrier transfer process under light irradiation (C). Figures taken from Ref. [1].