As a choke point in water electrolysis,the oxygen evolution reaction(OER)suffers from the severe electrode polarization and large overpotential.Herein,the porous hierarchical hetero-(Nis Fe)FeN/Ni catalysts are in sit...As a choke point in water electrolysis,the oxygen evolution reaction(OER)suffers from the severe electrode polarization and large overpotential.Herein,the porous hierarchical hetero-(Nis Fe)FeN/Ni catalysts are in situ constructed for the eficient electrocatalytic OER.X-ray absorption fine structure characterizations reveal the strong Ni-Fe bimetallic interaction in(Niz Fex)FeN/Ni.Theoretical study indicates the heterojunction and bimetallic interaction decrease the free-energy change for the rate-limiting step of the OER and the overpotential thereof.In addition,the high conductivity and porous hierarchical morphology favor the electron transfer,electrolyte access and O2 release.Consequently,the optimized catalyst achieves a low overpotential of 223 mV at 10 mA.cm^-2,a small Tafel slope of 68 mV:dec^-1,and a high stability.The excellent performance of the optimized catalyst is also demonstrated by the overall water electrolysis with a low working voltage and high Faradaic efficiency.Moreover,the correlation between the structure and performance is well established by the experimental characterizations and theoretical calculations,which confirms the origin of the OER activity from the surface metal oxyhydroxide in situ generated upon applying the current.This study suggests a promising approach to the advanced OER electrocatalysts for practical applications by constructing the porous hierarchical metal-compound/metal heterojunctions.展开更多
Metal-nitrogen-carbon materials are promising catalysts for CO2 electroreduction to CO. Herein, by taking the unique hierarchical carbon nanocages as the support, an advanced nickel-nitrogen-carbon single-site catalys...Metal-nitrogen-carbon materials are promising catalysts for CO2 electroreduction to CO. Herein, by taking the unique hierarchical carbon nanocages as the support, an advanced nickel-nitrogen-carbon single-site catalyst is conveniently prepared by pyrolyzing the mixture of NiCl2 and phenanthroline, which exhibits a Faradaic efficiency plateau of > 87% in a wide potential window of −0.6 – −1.0 V. Further S-doping by adding KSCN into the precursor much enhances the CO specific current density by 68%, up to 37.5 A·g−1 at −0.8 V, along with an improved CO Faradaic efficiency plateau of > 90%. Such an enhancement can be ascribed to the facilitated CO pathway and suppressed hydrogen evolution from thermodynamic viewpoint as well as the increased electroactive surface area and improved charge transfer fromkinetic viewpoint due to the S-doping. This study demonstrates a simple and effective approach to advanced electrocatalysts by synergetic modification of the porous carbon-based support and electronic structure of the active sites.展开更多
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
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.21832003,21773111,51571110,and 21573107)the Fundamental Research Funds for the Central Universities(No.020514380126).
文摘As a choke point in water electrolysis,the oxygen evolution reaction(OER)suffers from the severe electrode polarization and large overpotential.Herein,the porous hierarchical hetero-(Nis Fe)FeN/Ni catalysts are in situ constructed for the eficient electrocatalytic OER.X-ray absorption fine structure characterizations reveal the strong Ni-Fe bimetallic interaction in(Niz Fex)FeN/Ni.Theoretical study indicates the heterojunction and bimetallic interaction decrease the free-energy change for the rate-limiting step of the OER and the overpotential thereof.In addition,the high conductivity and porous hierarchical morphology favor the electron transfer,electrolyte access and O2 release.Consequently,the optimized catalyst achieves a low overpotential of 223 mV at 10 mA.cm^-2,a small Tafel slope of 68 mV:dec^-1,and a high stability.The excellent performance of the optimized catalyst is also demonstrated by the overall water electrolysis with a low working voltage and high Faradaic efficiency.Moreover,the correlation between the structure and performance is well established by the experimental characterizations and theoretical calculations,which confirms the origin of the OER activity from the surface metal oxyhydroxide in situ generated upon applying the current.This study suggests a promising approach to the advanced OER electrocatalysts for practical applications by constructing the porous hierarchical metal-compound/metal heterojunctions.
基金the National Key Research and Development Program of China(Nos.2017 YFA0206500 and 2018YFA0209103)the National Natural Science Foundation of China(Nos.21832003,21773111,21972061,51571110,and 21573107).The numerical calculations have been done on the computing facilities in the High Performance Computing Center(HPCC)of Nanjing University.
文摘Metal-nitrogen-carbon materials are promising catalysts for CO2 electroreduction to CO. Herein, by taking the unique hierarchical carbon nanocages as the support, an advanced nickel-nitrogen-carbon single-site catalyst is conveniently prepared by pyrolyzing the mixture of NiCl2 and phenanthroline, which exhibits a Faradaic efficiency plateau of > 87% in a wide potential window of −0.6 – −1.0 V. Further S-doping by adding KSCN into the precursor much enhances the CO specific current density by 68%, up to 37.5 A·g−1 at −0.8 V, along with an improved CO Faradaic efficiency plateau of > 90%. Such an enhancement can be ascribed to the facilitated CO pathway and suppressed hydrogen evolution from thermodynamic viewpoint as well as the increased electroactive surface area and improved charge transfer fromkinetic viewpoint due to the S-doping. This study demonstrates a simple and effective approach to advanced electrocatalysts by synergetic modification of the porous carbon-based support and electronic structure of the active sites.
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.
