The electrocatalytic N_(2)reduction reaction(NRR)is expected to supersede the traditional Haber-Bosch technology for NH3 production under ambient conditions.The activity and selectivity of electrochemical NRR are rest...The electrocatalytic N_(2)reduction reaction(NRR)is expected to supersede the traditional Haber-Bosch technology for NH3 production under ambient conditions.The activity and selectivity of electrochemical NRR are restricted to a strong polarized electric field induced by the catalyst,correct electron transfer direction,and electron tunneling distance between bare electrode and active sites.By coupling the chemical vapor deposition method with the poly(methyl methacylate)-transfer method,an ultrathin sandwich catalyst,i.e.,Fe atoms(polarized electric field layer)sandwiched between ultrathin(within electron tunneling distance)BN(catalyst layer)and graphene film(conducting layer),is fabricated for electrocatalytic NRR.The sandwich catalyst not only controls the transfer of electrons to the BN surface in the correct direction under applied voltage but also suppresses hydrogen evolution reaction by constructing a neutral polarization electric field without metal exposure.The sandwich electrocatalyst NRR system achieve NH3 yield of 8.9μg h^(−1)cm^(−2)and Faradaic Efficiency of 21.7%.The N_(2)adsorption,activation,and polarization electric field changes of three sandwich catalysts(BN-Fe-G,BN-Fe-BN,and G-Fe-G)during the electrocatalytic NRR are investigated by experiments and density functional theory simulations.Driven by applied voltage,the neutral polarized electric field induced by BN-Fe-G leads to the high activity of electrocatalytic NRR.展开更多
This study on the band structures and charge densities of nitrogen (N)-, carbon (C)- and boron (B)-doped titanium dioxide (TiO2) by first-principles simulation with the CASTEP code (Segall et al., 2002) showed that th...This study on the band structures and charge densities of nitrogen (N)-, carbon (C)- and boron (B)-doped titanium dioxide (TiO2) by first-principles simulation with the CASTEP code (Segall et al., 2002) showed that the three 2p bands of im-purity atom are located above the valence-band maximum and below the Ti 3d bands, and that along with the decreasing of im-purity atomic number, the fluctuations become more intensive. We cannot observe obvious band-gap narrowing in our result. Therefore, the cause of absorption in visible light might be the isolated impurity atom 2p states in band-gap rather than the band-gap narrowing.展开更多
Graphitic carbon nitride quantum dots(CNQDs) are emerging as attractive photoluminescent(PL)materials with excellent application potential in fluorescence imaging and heavy-metal ion detection. However, three limitati...Graphitic carbon nitride quantum dots(CNQDs) are emerging as attractive photoluminescent(PL)materials with excellent application potential in fluorescence imaging and heavy-metal ion detection. However, three limitations, namely, low quantum yields(QYs), self-quenching,and excitation-dependent PL emission behaviors, severely impede the commercial applications of crystalline CNQDs.Here we address these three challenges by synthesizing borondoped amorphous CNQDs via a hydrothermal process followed by the top±down cutting approach. Structural disorder endows the amorphous boron-doped CNQDs(B-CNQDs)with superior elastic strain performance over a wide range of pH values, thus effectively promoting mass transport and reducing exciton quenching. Boron as a dopant could fine-tune the electronic structure and emission properties of the PL material to achieve excitation-independent emission via the formation of uniform boron states. As a result, the amorphous B-CNQDs show unprecedented fluorescent stability(i.e., no obvious fading after two years) and a high QY of 87.4%;these values indicate that the quantum dots obtained are very promising fluorescent materials. Moreover, the B-CNQDs show bright-blue fluorescence under ultraviolet excitation when applied as ink on commercially available paper and are capable of the selective and sensitive detection of Fe^(2+) and Cd^(2+) in the parts-per-billion range. This work presents a novel avenue and scientific insights on amorphous carbon-based fluorescent materials for photoelectrical devices and sensors.展开更多
文摘The electrocatalytic N_(2)reduction reaction(NRR)is expected to supersede the traditional Haber-Bosch technology for NH3 production under ambient conditions.The activity and selectivity of electrochemical NRR are restricted to a strong polarized electric field induced by the catalyst,correct electron transfer direction,and electron tunneling distance between bare electrode and active sites.By coupling the chemical vapor deposition method with the poly(methyl methacylate)-transfer method,an ultrathin sandwich catalyst,i.e.,Fe atoms(polarized electric field layer)sandwiched between ultrathin(within electron tunneling distance)BN(catalyst layer)and graphene film(conducting layer),is fabricated for electrocatalytic NRR.The sandwich catalyst not only controls the transfer of electrons to the BN surface in the correct direction under applied voltage but also suppresses hydrogen evolution reaction by constructing a neutral polarization electric field without metal exposure.The sandwich electrocatalyst NRR system achieve NH3 yield of 8.9μg h^(−1)cm^(−2)and Faradaic Efficiency of 21.7%.The N_(2)adsorption,activation,and polarization electric field changes of three sandwich catalysts(BN-Fe-G,BN-Fe-BN,and G-Fe-G)during the electrocatalytic NRR are investigated by experiments and density functional theory simulations.Driven by applied voltage,the neutral polarized electric field induced by BN-Fe-G leads to the high activity of electrocatalytic NRR.
基金Project (No. 2004AA32G040) supported by the Hi-Tech Researchand Development Program (863) of China
文摘This study on the band structures and charge densities of nitrogen (N)-, carbon (C)- and boron (B)-doped titanium dioxide (TiO2) by first-principles simulation with the CASTEP code (Segall et al., 2002) showed that the three 2p bands of im-purity atom are located above the valence-band maximum and below the Ti 3d bands, and that along with the decreasing of im-purity atomic number, the fluctuations become more intensive. We cannot observe obvious band-gap narrowing in our result. Therefore, the cause of absorption in visible light might be the isolated impurity atom 2p states in band-gap rather than the band-gap narrowing.
基金supported by the National Natural Science Foundation of China (51772085 and 12072110)the Natural Science Foundation of Hunan Province (2020JJ4190)。
文摘Graphitic carbon nitride quantum dots(CNQDs) are emerging as attractive photoluminescent(PL)materials with excellent application potential in fluorescence imaging and heavy-metal ion detection. However, three limitations, namely, low quantum yields(QYs), self-quenching,and excitation-dependent PL emission behaviors, severely impede the commercial applications of crystalline CNQDs.Here we address these three challenges by synthesizing borondoped amorphous CNQDs via a hydrothermal process followed by the top±down cutting approach. Structural disorder endows the amorphous boron-doped CNQDs(B-CNQDs)with superior elastic strain performance over a wide range of pH values, thus effectively promoting mass transport and reducing exciton quenching. Boron as a dopant could fine-tune the electronic structure and emission properties of the PL material to achieve excitation-independent emission via the formation of uniform boron states. As a result, the amorphous B-CNQDs show unprecedented fluorescent stability(i.e., no obvious fading after two years) and a high QY of 87.4%;these values indicate that the quantum dots obtained are very promising fluorescent materials. Moreover, the B-CNQDs show bright-blue fluorescence under ultraviolet excitation when applied as ink on commercially available paper and are capable of the selective and sensitive detection of Fe^(2+) and Cd^(2+) in the parts-per-billion range. This work presents a novel avenue and scientific insights on amorphous carbon-based fluorescent materials for photoelectrical devices and sensors.
