Zengxin Pu,Bing Xiao,Siman Mao,Yingxue Sun,Dandan Ma,Hongkang Wang,Jun Zhou,Yonghong Cheng,Jian-Wen Shi
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-C 3 N 4 (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 H 2 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.
Huijie Li,Jingli Zhao,Yan Geng,Zhongjun Li,Yike Li,Jianshe Wang
CoP/g-C 3 N 4 , a kind of noble-metal-free binary photocatalyst , has been demonstrated to be active for water splitting. However, high recombination rate of charge carriers is still one of the biggest factors to restrict the photoactivity of CoP/g-C 3 N 4 . In this paper, Boron doped g-C 3 N 4 nanodots (BCNDs) were introduced to CoP/g-C 3 N 4 nanosheets (CoP/CNNS) and a novel CoP/BCNDs/CNNS ternary photocatalyst was constructed. Experimental characterization and testing results indicate that BCNDs/CNNS heterojunction was formed in CoP/BCNDs/CNNS ternary photocatalyst. Comparing with CoP/g-C 3 N 4 , CoP/BCNDs/CNNS facilitates electron-hole separation, and the photocatalytic hydrogen evolution rate can reach 1332.81 μmolg −1 ·h −1 , which is approximately 9.7 times as high as CoP/CNNS. It owns an apparent quantum efficiency of 10.78% at 420 nm. This work would provide a novel strategy to construct high activity g-C 3 N 4 based catalyst without noble metals.
How to overcome the intrinsic low activity of most oxidase and peroxidase mimics at neutral pH has been extremely challenging. Herein, we represent a chromium-mediated and ligand-dependent strategy to activate the oxidase-like activity of boron-doped g-C3N4 (B-g-C3N4, denoted as BG), aiming at breaking the pH limitation. Cr (III) can be in situ oxidized to Cr (IV) by generated •O2– upon UV light irradiation, which then works as a catalysis mediator to oxidize TMB under a neutral environment. Excitingly, the TMB oxidation can be rationally modulated by ligands on the BG coordinating with chromium. We verify that the PEI-Cr3+ coordination outperformed Cit-PEI-Cr3+ on the oxidase-like activity through a more accelerated electron transfer, unveiled by the Gauss theoretical calculations. This study highlights a paradigm of tuning the coordination environment on nanozyme surface via the ligand engineering strategy for boosting the oxidase-mimicking activity and breaking the pH limitation. Meanwhile, the catalysis-based colorimetric assay for accurate and selective identification of Cr3+ was achieved.
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