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Featured researches published by Chaojun Lei.


Journal of Materials Chemistry | 2018

An ultrathin cobalt-based zeolitic imidazolate framework nanosheet array with a strong synergistic effect towards the efficient oxygen evolution reaction

Junhui Cao; Chaojun Lei; Jian Yang; Xiaodi Cheng; Zhongjian Li; Bin Yang; Xingwang Zhang; Lecheng Lei; Yang Hou; K. Ostrikov

Development of highly efficient and stable zeolitic imidazolate framework (ZIF) nanosheets has recently received growing interest as alternatives to noble-metal electrocatalysts towards the oxygen evolution reaction (OER). Herein, we develop a novel vapor-phase hydrothermal growth strategy for in situ synthesis of ultrathin cobalt-based zeolitic imidazolate framework (ZIF-67) nanosheets grown on the surface of Co(OH)2 nanosheets vertically aligned on electrochemically exfoliated graphene (EG) foil. Ultrathin ZIF-67 nanosheets with a thickness of ∼5 nm are uniformly coated on the surface of a Co(OH)2 nanosheet array to form a 2D core–shell structure. Benefitting from the strong coupling and synergistic effects, the resulting EG/Co(OH)2/ZIF-67 hybrid exhibits excellent catalytic activity for the OER in alkaline electrolytes, which only requires an overpotential of 280 mV to attain a current density of 10 mA cm−2 with a low Tafel slope of 63 mV dec−1 and high stability. Such high OER performance for the EG/Co(OH)2/ZIF-67 hybrid is superior to that of commercial Ir/C catalysts and even better than that of all previously reported ZIF-based OER electrocatalysts. In situ Raman analyses demonstrate that under OER conditions, the Co–O species are converted into Co–OOH groups, which are responsible for the excellent catalytic activity of EG/Co(OH)2/ZIF-67 in the OER.


Energy and Environmental Science | 2018

Efficient alkaline hydrogen evolution on atomically dispersed Ni–Nx Species anchored porous carbon with embedded Ni nanoparticles by accelerating water dissociation kinetics

Chaojun Lei; Yu Wang; Yang Hou; Pan Liu; Jian Yang; Tao Zhang; Xiaodong Zhuang; Mingwei Chen; Bin Yang; Lecheng Lei; Chris Yuan; Ming Qiu; Xinliang Feng

Developing inexpensive and efficient electrocatalysts for hydrogen evolution reaction (HER) during alkaline water electrolysis is crucial for renewable and sustainable energy harvesting. Herein, we report a novel hybrid electrocatalyst comprising atomically dispersed Ni–Nx species anchored porous carbon (Ni–N–C) matrix with embedded Ni nanoparticles for HER. This new catalyst is synthesized via pyrolysis of hydrothermally prepared supermolecular composite of dicyandiamide and Ni ions followed by an acid etching treatment. The achieved hybrid exhibits superior catalytic performance toward HER with a small overpotential of 147 mV at 10 mA cm−2 and a low Tafel slope of 114 mV dec−1, comparable to those of state-of-the-art heteroatom-doped nanocarbon catalysts and even outperforming other reported transition-metal-based compounds in basic media. Experimental observations and theoretical calculations reveal that the presence of Ni nanoparticles can optimize surface states of Ni−Nx active centers and reduce energy barriers of dissociated water molecules, which synergistically improve OH− adsorption and promote HER kinetics. When served as electrodes for both cathode and anode, an alkaline water electrolyzer could afford a current density of 10 mA cm−2 at a low cell voltage of 1.58 V, rivalling the sufficiently high overpotentials of integrated Pt/C–Ir/C benchmark electrodes.


Chemsuschem | 2018

Porous Cobalt Oxynitride Nanosheets for Efficient Electrocatalytic Water Oxidation

Wei Liu; Yang Hou; Zhan Lin; Shikuan Yang; Chunlin Yu; Chaojun Lei; Xiaolin Wu; Denghong He; Qing Jia; Guokui Zheng; Xingwang Zhang; Lecheng Lei

Exploring efficient and cheap oxygen evolution reaction (OER) electrocatalysts is of great significance for electrochemical water splitting. Herein, we successfully prepared an efficient ternary electrocatalyst of porous cobalt oxynitride (Co3 Ox Ny ) nanosheets by a simple nitridation strategy. Specifically, CoON PNS-400 (cobalt oxynitride with porous nanosheet structure obtained at 400 o C) offered a low OER overpotential of 0.23 V to achieve the catalytic current density of 10 mA cm-2 and a small Tafel slope of 48 mV dec-1 in alkali media, outperforming most of the first-row transition-metal-based OER electrocatalysts. The calculated density of states (DOS) analysis and electron spin resonance (ESR) measurements revealed that the introduction of foreign N atoms into pristine Co3 O4 nanosheets can optimize the electronic structure and create more oxygen vacancies, thus leading to enhanced electrical conductivity. Density functional theory (DFT) calculations demonstrated that the foreign N atoms can also improve the energetics for OER by modulating the free energy for adsorbed intermediates (OOH*, OH*, O*), further improving the OER electrocatalytic activity of CoON PNS-400. This work provides a possibility for rationally designing ternary transition-metal compounds as advanced OER electrocatalysts.


Chemosphere | 2018

Electrochemical activation of sulfate by BDD anode in basic medium for efficient removal of organic pollutants

Luchuan Chen; Chaojun Lei; Zhongjian Li; Bin Yang; Xingwang Zhang; Lecheng Lei

Electrochemical advanced oxidation processes (EAOPs) based on hydroxyl radicals (OH) have some limitations when they are applied to real wastewater treatment, such like strict requirements on pH (acidic electrolyte) and high energy consumption. Compared to OH, Sulfate radicals (SO4-) have high redox potential in wider range of pH (2-9). In this study, SO4- were efficiently produced by electrochemical activation of SO42- at boron doped diamond (BDD) anode. The degradation rate of 2,4-DCP (k = 0.828 ± 0.05 h-1) in the presence of Na2SO4 was approximately 4 times than that without Na2SO4 (k = 0.219 ± 0.01 h-1), indicating that SO4- exhibited higher reactivity than OH at initial pH = 9. Moreover, the amount of O2 decreased by 65% after 100 min during electro-oxidation of 2,4-DCP and the specific energy consumption per unit TOC (ECTOC) was reduced by 70% when the concentration of Na2SO4 increased from 0.01 to 0.1 M. The impact of sulfate ions in the electrochemical advanced oxidation were investigated. Electron spin resonance (ESR) measurements were conducted to identify the formation of SO4-. Electrolysis of 2,4-DCP with specific radical scavengers (ethanol and tert-Butanol) were conducted and the results revealed that SO4- were mainly produced by one-electron loss of sulfate at basic condition. Electro-generation persulfate was measured and participation of non-radical activation of persulfate was investigated. O2 production was quantified and we found electrochemical activation of sulfate could inhibit water dissociation. Taken all findings, a mechanism of electrochemical activation of sulfate at BDD anode was summarized. This technology eliminates the requirement for pH adjustment for wastewater treatment and makes EAOPs more effective and economic as well.


Advanced Energy Materials | 2018

FeN4 Sites Embedded into Carbon Nanofiber Integrated with Electrochemically Exfoliated Graphene for Oxygen Evolution in Acidic Medium

Chaojun Lei; Hengquan Chen; Junhui Cao; Jian Yang; Ming Qiu; Ying Xia; Chris Yuan; Bin Yang; Zhongjian Li; Xingwang Zhang; Lecheng Lei; Janel Abbott; Yu Zhong; Xinhui Xia; Gang Wu; Qinggang He; Yang Hou


ACS Sustainable Chemistry & Engineering | 2018

Nitrogen Vacancy Structure Driven Photoeletrocatalytic Degradation of 4-Chlorophenol Using Porous Graphitic Carbon Nitride Nanosheets

Yang Hou; Jian Yang; Chaojun Lei; Bin Yang; Zhongjian Li; Yu Xie; Xingwang Zhang; Lecheng Lei; Junhong Chen


Chinese Chemical Letters | 2017

CuS/RGO hybrid by one-pot hydrothermal method for efficient electrochemical sensing of hydrogen peroxide

Wei Liu; Chaojun Lei; Hongxiu Zhang; Xiaolin Wu; Qing Jia; Denghong He; Bin Yang; Zhongjian Li; Yang Hou; Lecheng Lei; Xingwang Zhang


ACS Sustainable Chemistry & Engineering | 2018

Metal Organic Framework Derived Fe-doped CoSe2 Incorporated in Nitrogen-doped Carbon Hybrid for Efficient Hydrogen Evolution

Xiaolin Wu; Song Han; Denghong He; Chunlin Yu; Chaojun Lei; Wei Liu; Guokui Zheng; Xingwang Zhang; Lecheng Lei


Journal of The Electrochemical Society | 2018

Evidence of the Strong Metal Support Interaction in a Palladium-Ceria Hybrid Electrocatalyst for Enhancement of the Hydrogen Evolution Reaction

Tengyang Gao; Jian Yang; Masahiko Nishijima; Hamish A. Miller; Francesco Vizza; Heyun Gu; Hengquan Chen; Yongfeng Hu; Zheng Jiang; Lin Wang; Ling Shuai; Ming Qiu; Chaojun Lei; Anyun Zhang; Yang Hou; Qinggang He


Journal of Energy Chemistry | 2018

High performance n + p-Si/Ti/NiS x O y photocathode for photoelectrochemical hydrogen evolution in alkaline solution

Qing Jia; Chunlin Yu; Wei Liu; Guokui Zheng; Chaojun Lei; Lecheng Lei; Xingwang Zhang

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