An electron-hole separation mechanism caused by the pseudo-gap formed at the interfacial Co-N bond between cobalt porphyrin metal organic framework and boron-doped g-C3N4 for boosting photocatalytic H2 production.

Photocatalytic hydrogen evolution from water splitting presents an attractive prospect in dealing with the energy crisis, but the low efficiency of charge separation and migration still seriously hinders its further practical application. Here, an acidified boron-doped g-C3N4 (HBCNN) and cobalt porphyrin metal organic frameworks (CoPMOF) self-assembled two-dimensional and two-dimensional (2D/2D) hybrid photocatalyst is fabricated successfully. The resultant HBCNN/CoPMOF with optimum ratio exhibits a superior H2 evolution rate of 33.17 mmol g-1 h-1, which is 3.04 and 100.50 times higher than the single HBCNN and CoPMOF, respectively. It is found that a coordination connection has formed between CoPMOF and HBCNN through Co-N bond, and the interfacial Co-N bond then forms a pseudo-gap in the up-spin channel of electronic states, establishing an electron-hole separation mechanism. It is this electron-hole separation mechanism that contributes to a Z-scheme transport mode of photogenerated carriers, which greatly promotes the photocatalytic H2 production performance of HBCNN/CoPMOF heterostructure. This work may provide an idea for the design of heterojunction to improve the photocatalytic performance by constructing electron-hole separation through interfacial bond.

Ultrahigh sorption and reduction of Cr(VI) by two novel core-shell composites combined with Fe3O4 and MoS2.

In this investigation, two novel magnetic core-shell Fe3O4@MoS2 (F@M) and MoS2@Fe3O4 (M@F) composites were synthesized and exploited for Cr(VI) elimination. Eco-friendly preparation methods were applied for the synthesis of Fe3O4 and MoS2 composites. The experimental results showed that both F@M and M@F have high saturation magnetization values (43.2 emu/g for F@M and 49.9 emu/g for M@F), excellent maximum sorption capacities of Cr(VI) at pH 5.0 and 298 K (324.3 mg/g for F@M, 290.2 mg/g for M@F), remarkable Cr(VI) removal efficiencies (Cr(VI) sorption equilibrium by both F@M and M@F can be reached in 90 min) and nice regeneration properties (the sorption capabilities of F@M and M@F decreased slightly after five consecutive sorption/desorption cycles). Chemical reduction of Cr(VI) to Cr(III) occurred on the surface of F@M and M@F, and the synergetic reduction of sulfur and ferrous ions made F@M an outstanding material for Cr(VI) removal. This paper highlights F@M and M@F as potential, eco-friendly and ultrahigh-efficiency materials for Cr(VI) pollution cleanup.