The neutral hydrogen evolution reaction(HER)is vital in the chemical industry,and its efficiency depends on the interior character of the catalyst.Herein,work function(WF)engineering is introduced via 3d metal(Fe,Co,N...The neutral hydrogen evolution reaction(HER)is vital in the chemical industry,and its efficiency depends on the interior character of the catalyst.Herein,work function(WF)engineering is introduced via 3d metal(Fe,Co,Ni,and Cu)doping for modulating the Fermi energy level of Mo2C.The defective energy level facilitates the free water molecule adsorption and,subsequently,promotes the neutral HER efficiency.Specifically,at a current density of 10 mA/cm2,Cu-Mo2C exhibits the best HER performance with an overpotential of 78 mV,followed by Ni-Mo2C,Co-Mo2C,Fe-Mo2C,and bare Mo2C with 90,95,100,and 173 mV,respectively,and the corresponding Tafel slope values are 40,43,42,56,and 102 mV/dec.The modified WF can also lead to an enhanced photocatalytic efficiency owing to the lowered Schottky barrier and excellent carrier transition across the electrocatalyst–solution interface.When coupling the metal-doped Mo2C samples with TiO2,enhanced photocatalytic neutral HER rates are obtained in comparison to the case with bare TiO2.Typically,the HER rates are 521,404,275,224,147,and 112μmol/h for Cu,Ni,Co,Fe,bare Mo2C,and bare TiO2,respectively.Time-resolved photoluminescence spectroscopy(TRPS)and ultrafast transient absorption(TA)measurements are carried out to confirm the recombination and migration of the photogenerated carriers.The fittedτvalues from the TRPS curves are 22.6,20.5,10.1,4.7,4.0,2.5,and 1.9 ns for TiO2,TiO2-Mo2C,TiO2-Fe-Mo2C,TiO2-Fe-Mo2C,TiO2-Fe-Mo2C,TiO2-Fe-Mo2C,and TiO2-Pt,respectively.Additionally,the fittedτvalues from the TA results are 31,73,and 105 ps for the TiO2-Mo2C,TiO2-Cu-Mo2C,and TiO2-Pt samples,respectively.This work provides in-depth insights into the WF modulation of an electrocatalyst for improving the HER performance.展开更多
We report a novel Mn-Co-Ni-O(MCN)nanocomposite in which the p-type semiconductivity of Mn-Co-Ni-O can be manipulated by addition of graphene.With an increase of graphene content,the semiconductivity of the nanocomposi...We report a novel Mn-Co-Ni-O(MCN)nanocomposite in which the p-type semiconductivity of Mn-Co-Ni-O can be manipulated by addition of graphene.With an increase of graphene content,the semiconductivity of the nanocomposite can be tuned from p-type through electrically neutral to n-type.The very low effective mass of electrons in graphene facilitates electron tunneling into the MCN,neutralizing holes in the MCN nanoparticles.XPS analysis shows that the multivalent manganese ions in the MCN nanoparticles are chemically reduced by the graphene electrons to lower-valent states.Unlike traditional semiconductor devices,electrons are excited from the filled graphite band into the empty band at the Dirac points from where they move freely in the graphene and tunnel into the MCN.The new composite film demonstrates inherent flexibility,high mobility,short carrier lifetime,and high carrier concentration.This work is useful not only in manufacturing flexible transistors,FETs,and thermosensitive and thermoelectric devices with unique properties but also in providing a new method for future development of 2D-based semiconductors.展开更多
We report a novel Mn-Co-Ni-O(MCN)nanocomposite in which the p-type semiconductivity of Mn-Co-Ni-O can be manipulated by addition of graphene.With an increase of graphene content,the semiconductivity of the nanocomposi...We report a novel Mn-Co-Ni-O(MCN)nanocomposite in which the p-type semiconductivity of Mn-Co-Ni-O can be manipulated by addition of graphene.With an increase of graphene content,the semiconductivity of the nanocomposite can be tuned from p-type through electrically neutral to n-type.The very low effective mass of electrons in graphene facilitates electron tunneling into the MCN,neutralizing holes in the MCN nanoparticles.XPS analysis shows that the multivalent manganese ions in the MCN nanoparticles are chemically reduced by the graphene electrons to lower-valent states.Unlike traditional semiconductor devices,electrons are excited from the filled graphite band into the empty band at the Dirac points from where they move freely in the graphene and tunnel into the MCN.The new composite film demonstrates inherent flexibility,high mobility,short carrier lifetime,and high carrier concentration.This work is useful not only in manufacturing flexible transistors,FETs,and thermosensitive and thermoelectric devices with unique properties but also in providing a new method for future development of 2D-based semiconductors.展开更多
文摘The neutral hydrogen evolution reaction(HER)is vital in the chemical industry,and its efficiency depends on the interior character of the catalyst.Herein,work function(WF)engineering is introduced via 3d metal(Fe,Co,Ni,and Cu)doping for modulating the Fermi energy level of Mo2C.The defective energy level facilitates the free water molecule adsorption and,subsequently,promotes the neutral HER efficiency.Specifically,at a current density of 10 mA/cm2,Cu-Mo2C exhibits the best HER performance with an overpotential of 78 mV,followed by Ni-Mo2C,Co-Mo2C,Fe-Mo2C,and bare Mo2C with 90,95,100,and 173 mV,respectively,and the corresponding Tafel slope values are 40,43,42,56,and 102 mV/dec.The modified WF can also lead to an enhanced photocatalytic efficiency owing to the lowered Schottky barrier and excellent carrier transition across the electrocatalyst–solution interface.When coupling the metal-doped Mo2C samples with TiO2,enhanced photocatalytic neutral HER rates are obtained in comparison to the case with bare TiO2.Typically,the HER rates are 521,404,275,224,147,and 112μmol/h for Cu,Ni,Co,Fe,bare Mo2C,and bare TiO2,respectively.Time-resolved photoluminescence spectroscopy(TRPS)and ultrafast transient absorption(TA)measurements are carried out to confirm the recombination and migration of the photogenerated carriers.The fittedτvalues from the TRPS curves are 22.6,20.5,10.1,4.7,4.0,2.5,and 1.9 ns for TiO2,TiO2-Mo2C,TiO2-Fe-Mo2C,TiO2-Fe-Mo2C,TiO2-Fe-Mo2C,TiO2-Fe-Mo2C,and TiO2-Pt,respectively.Additionally,the fittedτvalues from the TA results are 31,73,and 105 ps for the TiO2-Mo2C,TiO2-Cu-Mo2C,and TiO2-Pt samples,respectively.This work provides in-depth insights into the WF modulation of an electrocatalyst for improving the HER performance.
基金supported by theShaanxi Fundamental Education Research Funds for the Universities(2017e065201102)the Special Fund for Support by 2019 Guangdong Special Funds(2019B090904007).
文摘We report a novel Mn-Co-Ni-O(MCN)nanocomposite in which the p-type semiconductivity of Mn-Co-Ni-O can be manipulated by addition of graphene.With an increase of graphene content,the semiconductivity of the nanocomposite can be tuned from p-type through electrically neutral to n-type.The very low effective mass of electrons in graphene facilitates electron tunneling into the MCN,neutralizing holes in the MCN nanoparticles.XPS analysis shows that the multivalent manganese ions in the MCN nanoparticles are chemically reduced by the graphene electrons to lower-valent states.Unlike traditional semiconductor devices,electrons are excited from the filled graphite band into the empty band at the Dirac points from where they move freely in the graphene and tunnel into the MCN.The new composite film demonstrates inherent flexibility,high mobility,short carrier lifetime,and high carrier concentration.This work is useful not only in manufacturing flexible transistors,FETs,and thermosensitive and thermoelectric devices with unique properties but also in providing a new method for future development of 2D-based semiconductors.
基金supported by the Shaanxi Fundamental Education Research Funds for the Universities(2017e065201102)the Special Fund for Support by 2019 Guangdong Special Funds(2019B090904007).
文摘We report a novel Mn-Co-Ni-O(MCN)nanocomposite in which the p-type semiconductivity of Mn-Co-Ni-O can be manipulated by addition of graphene.With an increase of graphene content,the semiconductivity of the nanocomposite can be tuned from p-type through electrically neutral to n-type.The very low effective mass of electrons in graphene facilitates electron tunneling into the MCN,neutralizing holes in the MCN nanoparticles.XPS analysis shows that the multivalent manganese ions in the MCN nanoparticles are chemically reduced by the graphene electrons to lower-valent states.Unlike traditional semiconductor devices,electrons are excited from the filled graphite band into the empty band at the Dirac points from where they move freely in the graphene and tunnel into the MCN.The new composite film demonstrates inherent flexibility,high mobility,short carrier lifetime,and high carrier concentration.This work is useful not only in manufacturing flexible transistors,FETs,and thermosensitive and thermoelectric devices with unique properties but also in providing a new method for future development of 2D-based semiconductors.
