The investigation of earth-abundant electrocatalysts for efficient water electrolysis is of central importance in renewable energy system, which is currently impeded by the large overpotential of oxygen evolution reac...The investigation of earth-abundant electrocatalysts for efficient water electrolysis is of central importance in renewable energy system, which is currently impeded by the large overpotential of oxygen evolution reaction (OER). NiFe sulfides show promising OER activity but are troubled by their low intrinsic conductivities. Herein, we demonstrate the construction of the porous core-shell heterojunctions of FeNi3@(Fe,Ni)S_(2) with tunable shell thickness via the reduction of hierarchical NiFe(OH)x nanosheets followed by a partial sulfidization. The conductive FeNi3 core provides the highway for electron transport, and the (Fe,Ni)S_(2) shell offers the exposed surface for in situ generation of S-doped NiFe-oxyhydroxides with high intrinsic OER activity, which is supported by the combined experimental and theoretical studies. In addition, the porous hierarchical morphology favors the electrolyte access and O_(2) liberation. Consequently, the optimized catalyst achieves an excellent OER performance with a low overpotential of 288 mV at 100 mA·cm^(−2), a small Tafel slope of 48 mV·dec^(−1), and a high OER durability for at least 1,200 h at 200 mA·cm^(−2). This study provides an effective way to explore the advanced earth-abundant OER electrocatalysts by constructing the heterojunctions between metal and corresponding metal-compounds via the convenient post treatment, such as nitridation and sulfidization.展开更多
The purpose of this study was to prepare a proof-of-concept CO_(2) adsorbing material based on a new amine grafted silica aerogel microsphere(AGSAM)that could be used on both fixed and fluidized beds.A low-cost water ...The purpose of this study was to prepare a proof-of-concept CO_(2) adsorbing material based on a new amine grafted silica aerogel microsphere(AGSAM)that could be used on both fixed and fluidized beds.A low-cost water glass and environment-friendly water were used as precursor and solvent of the silica aerogel,respectively.The silica aerogel microsphere(SAM)was prepared by dropping the siliceous solution into hot oil bath.The effect of the pH value of the siliceous solution,stirring speed and stirring paddle position on the sphericity and size of the SAM was investigated.The SAM with good sphericity was obtained when the pH value was 5.69–5.79.The mean diameter of the SAM decreased from 5 to 1 mm when the stirring speed increased from 1000 to 2000 rpm.The SAM with excellent sphericity was prepared when the paddle was placed on the top of the oil bath.When the paddle was placed at the middle and bottom of the oil bath,some liquid drops aggregated together and formed large aggregations.AGSAM was obtained by grafting the amine groups onto the framework of the silica gel microsphere.The CO2 adsorption capacity of the AGSAM was 1.04 mmol g^(-1) with 1%CO2 at 300 mL min^(-1).The AGSAM with 4,3.2,2 and 1 mm in diameters had the fluidizing velocities of 0.531,0.425,0.265 and 0.159 m s^(-1),respectively.The AGSAM with different sizes met different fluidizing conditions.展开更多
基金This work was jointly supported by the National Key Research and Development Program of China (Nos. 2017YFA0206500 and 2018YFA0209103)the National Natural Science Foundation of China (Nos. 52071174, 21832003, 21773111, and 21972061)+1 种基金the Fundamental Research Funds for the Central Universities (No. 020514380126)The numerical calculations have been done on the computing facilities in the High Performance Computing Center (HPCC) of Nanjing University. We thank the staff of the BL14W1 beamline at Shanghai Synchrotron Radiation Facility for assistance with the X-ray absorption measurements.
文摘The investigation of earth-abundant electrocatalysts for efficient water electrolysis is of central importance in renewable energy system, which is currently impeded by the large overpotential of oxygen evolution reaction (OER). NiFe sulfides show promising OER activity but are troubled by their low intrinsic conductivities. Herein, we demonstrate the construction of the porous core-shell heterojunctions of FeNi3@(Fe,Ni)S_(2) with tunable shell thickness via the reduction of hierarchical NiFe(OH)x nanosheets followed by a partial sulfidization. The conductive FeNi3 core provides the highway for electron transport, and the (Fe,Ni)S_(2) shell offers the exposed surface for in situ generation of S-doped NiFe-oxyhydroxides with high intrinsic OER activity, which is supported by the combined experimental and theoretical studies. In addition, the porous hierarchical morphology favors the electrolyte access and O_(2) liberation. Consequently, the optimized catalyst achieves an excellent OER performance with a low overpotential of 288 mV at 100 mA·cm^(−2), a small Tafel slope of 48 mV·dec^(−1), and a high OER durability for at least 1,200 h at 200 mA·cm^(−2). This study provides an effective way to explore the advanced earth-abundant OER electrocatalysts by constructing the heterojunctions between metal and corresponding metal-compounds via the convenient post treatment, such as nitridation and sulfidization.
基金supports from the National Natural Science Foundation of China(51602151)the Natural Science Foundation of Jiangsu Province-China(BK20161003)+1 种基金the Project funded by China Postdoctoral Science Foundation(2018T110490,2018M642228)the Priority Academic Program Development of Jiangsu Higher Education Institution(PAPD)-China.
文摘The purpose of this study was to prepare a proof-of-concept CO_(2) adsorbing material based on a new amine grafted silica aerogel microsphere(AGSAM)that could be used on both fixed and fluidized beds.A low-cost water glass and environment-friendly water were used as precursor and solvent of the silica aerogel,respectively.The silica aerogel microsphere(SAM)was prepared by dropping the siliceous solution into hot oil bath.The effect of the pH value of the siliceous solution,stirring speed and stirring paddle position on the sphericity and size of the SAM was investigated.The SAM with good sphericity was obtained when the pH value was 5.69–5.79.The mean diameter of the SAM decreased from 5 to 1 mm when the stirring speed increased from 1000 to 2000 rpm.The SAM with excellent sphericity was prepared when the paddle was placed on the top of the oil bath.When the paddle was placed at the middle and bottom of the oil bath,some liquid drops aggregated together and formed large aggregations.AGSAM was obtained by grafting the amine groups onto the framework of the silica gel microsphere.The CO2 adsorption capacity of the AGSAM was 1.04 mmol g^(-1) with 1%CO2 at 300 mL min^(-1).The AGSAM with 4,3.2,2 and 1 mm in diameters had the fluidizing velocities of 0.531,0.425,0.265 and 0.159 m s^(-1),respectively.The AGSAM with different sizes met different fluidizing conditions.
