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Graphical abstract Distinctive ternary CdS/Ni 2 P/g-C 3 N 4 photocatalyst achieved outstanding photocatalytic activity for overall water splitting via the Ni 2 P electron-bridge to separate the photocarriers efficiently. Highlights • Distinctive ternary CdS/Ni 2 P/g-C 3 N 4 composite was constructed successfully. • CdS/Ni 2 P/g-C 3 N 4 displayed excellent photocatalytic overall water splitting activity. • CdS/Ni 2 P/g-C 3 N 4 composite had efficient separation efficiency of photocarriers. • Ni 2 P strengthened the electron transfer performance from g-C 3 N 4 to CdS. Abstract Efficient overall water splitting over semiconductor photocatalyst is vital but difficult for resolving the energy and environmental crises. In this report, a novel transition metal phosphide Ni 2 P-based ternary CdS/Ni 2 P/g-C 3 N 4 composite was constructed for achieving efficient overall water splitting activity under visible light (λ > 420 nm). The H 2 and O 2 evolution ratios are 15.56 and 7.75 μmol·g–1 h–1 over CdS/Ni 2 P/g-C 3 N 4 with 3 wt% Ni 2 P, respectively, which is 4.02 times higher than that of binary type II CdS/g-C 3 N 4. The separation efficiency of photocarriers of CdS/Ni 2 P/g-C 3 N 4 is enhanced through greatly speeding up the transfer efficiency of electrons from the conduction band of g-C 3 N 4 to that of CdS using Ni 2 P as electron-bridge, proved by the photoluminescence, transient photocurrent measurements and electrochemical impendence spectroscopy. The significant finding of this paper sheds light on the important role of transition metal phosphide as electron-bridge to connect the two conduction bands of type II semiconductor heterojuction for strengthening the separation efficiency of photocarriers. [ABSTRACT FROM AUTHOR]

The Z-scheme heterojunction has great potential in synchronous CO 2 reduction and tetracycline degradation due to its strong redox capacity. However, the high interfacial migration resistance severely restricts its practical application. Herein, a difunctional Ni 2 P, as an electron-bridge and co-catalyst, was rationally introduced into the BiVO 4 /g-C 3 N 4 Z-scheme system to reduce interfacial transfer resistance, which presented a better photocatalytic property than that of BiVO 4 /g-C 3 N 4 heterojunction. What is more, the difunctional roles of Ni 2 P in boosting photocatalytic activity were deeply discussed. Obviously, the metallic Ni 2 P, as an electron-bridge could effectively reduce the interfacial migration resistance of electrons, meanwhile, as a co-catalyst on the surface of g-C 3 N 4 not only accelerated separation and migration of carriers, but also increased more active sites for CO 2 reduction, thereby, maximizing the separation efficiency of carriers. This work highlighted the synergistic effect of transition metal phosphides electron-bridge and co-catalyst to design efficient photocatalysts for environment and energy applications. [Display omitted] • A difunctional Ni 2 P was rationally introduced into the BiVO 4 /g-C 3 N 4 Z-scheme system. • Ni 2 P as an electron-bridge could effectively reduce the interfacial migration resistance of electrons. • Ni 2 P as a co-catalyst on the surface of g-C 3 N 4 could increase more active sites for CO 2 reduction. • The difunctional Ni 2 P synergistically boosted the photocatalytic CO 2 reduction and TC oxidation. • Coupled reaction system realized the full utilization of the charges. [ABSTRACT FROM AUTHOR]

• Carbon materials was obtained from green tea and acted as the electron transfer medium to effectively enhance photocatalytic performance. • Charge was transferred through dual paths. • The Ni 2 P and CDs were all acted as the active sites for improving the photocatalytic performance. Carbon materials can act as electron transfer media to effectively enhance photocatalytic performance. In this study, carbon dots (CDs) were prepared using green tea to modify Ni 2 P/NiCo-LDH heterostructures. Benefitting from the Co-P bond formed between Ni 2 P and NiCo-LDH and biomass CDs, charge transfer was improved via dual channel. Ni 2 P and CDs acted as active sites for improving the photocatalytic performance. Owing to the synergistic process, the photoresponse capability of CDs/Ni 2 P/NiCo-LDH was significantly increased. In addition, the possible active species in the photocatalytic process are discussed. This study provides a design for ternary photocatalysts with carbon materials and phosphides. [Display omitted] [ABSTRACT FROM AUTHOR]