Hollow and porous Pt-based nanomaterials are promising catalysts with applications in many sustainable energy technologies such as fuel cells. Economical and green synthetic routes are highly desirable. Here, we repor...Hollow and porous Pt-based nanomaterials are promising catalysts with applications in many sustainable energy technologies such as fuel cells. Economical and green synthetic routes are highly desirable. Here, we report a facile approach to prepare double- and single-layered Pt-Ni nanobowls （DLNBs and SLNBs） with porous shells. Microstructural analysis revealed that the shells were constructed of alloyed Pt-Ni nanocrystals and small amounts of Ni compounds. X-ray photoelectron spectra showed that their Pt 4f binding energies shifted in the negative direction compared to those of the commercial Pt/C catalyst. Furthermore, the DLNBs contained greater contents of oxidized Ni species than the SLNBs. The layer-controlled growth processes were confirmed by microscopy, and a formation mechanism was proposed based on the assistance of citrate and poly（vinylpyrrolidone） （PVP）. For the methanol oxidation reaction, the DLNBs and SLNBs exhibited 2.9 and 2.5 times higher mass activities than that of the commercial Pt/C catalyst, respectively. The activity enhancements were attributed to electronic effects and a bifunctional mechanism. Chronoamperometry and prolonged cyclic voltammetry indicated that the Pt-Ni bowl-like structures had better electrochemical properties and structural stability than the commercial Pt/C catalyst, thus making the Pt-Ni nanobowls excellent electrocatalysts for use in direct methanol fuel cells.展开更多
Hierarchical Ag/SiO_(2)/TiO_(2) nanobowl(NB)arrays were fabricated for use as plasmonic photoanodes for solar-hydrogen conversion.The nanobowls had large pore size and were composed of an upper TiO_(2) nanoring and a ...Hierarchical Ag/SiO_(2)/TiO_(2) nanobowl(NB)arrays were fabricated for use as plasmonic photoanodes for solar-hydrogen conversion.The nanobowls had large pore size and were composed of an upper TiO_(2) nanoring and a lower TiO_(2) nanohole.A thin SiO_(2) inter-layer was introduced as an electron transmission channel to change the mechanism of hot electron transport.Simulations were performed to characterize the variation of electron concentration in Ag/SiO_(2)/TiO_(2) NB arrays,taking into account both the optical transition of photogenerated electrons,and electron tunneling.The multiphysics coupling function of COMSOL software provided the light source for optical transition of photogenerated electrons,and a Wentzel-Kramers-Brillouin model was employed to represent the tunneling.The results demonstrate that the TiO_(2) nanoring was a transporter,which transmitted electrons downward to the nanohole.The SiO_(2) layer replaces the Schottky barrier to become a bridge for tunneling of hot electrons in high-and low-energy states into TiO_(2).Moreover,the coverage of the SiO_(2) layer helped increase the light absorption of TiO_(2),it also reduced the near electric field coupling between Ag and TiO_(2).Accordingly,under AM 1.5 light irradiation,the photocurrent density and average hydrogen evolution rate of Ag/SiO_(2)/TiO_(2) were 1.8 and 2.2 times higher,respectively,than those of pure TiO_(2),implying far more efficient migration of carriers.展开更多
基金Acknowledgements This work was supported by the National Natural Science Foundation of China （Nos. 51371015 and 51331002）, the Beijing Natural Science Foundation （No. 2142018） and the Fundamental Research Funds for the Central Universities （No. FRF-BR-15-009B）.
文摘Hollow and porous Pt-based nanomaterials are promising catalysts with applications in many sustainable energy technologies such as fuel cells. Economical and green synthetic routes are highly desirable. Here, we report a facile approach to prepare double- and single-layered Pt-Ni nanobowls （DLNBs and SLNBs） with porous shells. Microstructural analysis revealed that the shells were constructed of alloyed Pt-Ni nanocrystals and small amounts of Ni compounds. X-ray photoelectron spectra showed that their Pt 4f binding energies shifted in the negative direction compared to those of the commercial Pt/C catalyst. Furthermore, the DLNBs contained greater contents of oxidized Ni species than the SLNBs. The layer-controlled growth processes were confirmed by microscopy, and a formation mechanism was proposed based on the assistance of citrate and poly（vinylpyrrolidone） （PVP）. For the methanol oxidation reaction, the DLNBs and SLNBs exhibited 2.9 and 2.5 times higher mass activities than that of the commercial Pt/C catalyst, respectively. The activity enhancements were attributed to electronic effects and a bifunctional mechanism. Chronoamperometry and prolonged cyclic voltammetry indicated that the Pt-Ni bowl-like structures had better electrochemical properties and structural stability than the commercial Pt/C catalyst, thus making the Pt-Ni nanobowls excellent electrocatalysts for use in direct methanol fuel cells.
基金the National Natural Science Foundation of China(No.51776009)for their financial support.
文摘Hierarchical Ag/SiO_(2)/TiO_(2) nanobowl(NB)arrays were fabricated for use as plasmonic photoanodes for solar-hydrogen conversion.The nanobowls had large pore size and were composed of an upper TiO_(2) nanoring and a lower TiO_(2) nanohole.A thin SiO_(2) inter-layer was introduced as an electron transmission channel to change the mechanism of hot electron transport.Simulations were performed to characterize the variation of electron concentration in Ag/SiO_(2)/TiO_(2) NB arrays,taking into account both the optical transition of photogenerated electrons,and electron tunneling.The multiphysics coupling function of COMSOL software provided the light source for optical transition of photogenerated electrons,and a Wentzel-Kramers-Brillouin model was employed to represent the tunneling.The results demonstrate that the TiO_(2) nanoring was a transporter,which transmitted electrons downward to the nanohole.The SiO_(2) layer replaces the Schottky barrier to become a bridge for tunneling of hot electrons in high-and low-energy states into TiO_(2).Moreover,the coverage of the SiO_(2) layer helped increase the light absorption of TiO_(2),it also reduced the near electric field coupling between Ag and TiO_(2).Accordingly,under AM 1.5 light irradiation,the photocurrent density and average hydrogen evolution rate of Ag/SiO_(2)/TiO_(2) were 1.8 and 2.2 times higher,respectively,than those of pure TiO_(2),implying far more efficient migration of carriers.
