Direct Z-scheme WO_(3-x) nanowire-bridged TiO_(2) nanorod arrays for highly efficient photoelectrochemical overall water splitting

All-solid-state Z-scheme photocatalysts for overall water splitting to evolve H_(2) is a promising strategy for efficient conversion of solar energy.However,most of these strategies require redox mediators.Herein,a direct Z-scheme photoelectrocatalytic electrode based on a WO_(3-x)nanowire-bridged TiO_(2)nanorod array heterojunction is constructed for overall water splitting,producing H_(2).The as-prepared WO_(3-x)/TiO_(2)nanorod array heterojunction shows photoelectrochemical(PEC)overall water splitting activity evolving both H_(2) and O_(2)under UV-vis light irradiation.An optimum PEC activity was achieved over a 1.67-WO_(3-x)/TiO_(2)photoelectrode yielding maximum H_(2) and O_(2)evolution rates roughly 11 times higher than that of pure TiO_(2)nanorods without any sacrificial agent or redox mediator.The role of oxygen vacancy in WO_(3-x)in affecting the H_(2) production rate was also comprehensively studied.The superior PEC activity of the WO_(3-x)/TiO_(2)electrode for overall water splitting can be ascribed to an efficient Z-scheme charge transfer pathway between the WO_(3-x)nanowires and TiO_(2)nanorods,the presence of oxygen vacancies in WO_(3-x),and a bias potential applied on the photoelectrode,resulting in effective spatial charge separation.This study provides a novel strategy for developing highly efficient PECs for overall water splitting.

Electron transition manipulation under graphene-mediated plasmonic engineering nanostructure

Monolayer graphene has attracted enormous attention owing to its unique electronic and optical properties.However,achieving an effective approach without applying electrical bias for manipulating the charge transfer based on graphene is elusive to date.Herein,we realized the manipulation of excitons’transition from emitter to the graphene surface with plasmonic engineering nanostructures and firstly obtained large enhancements for photon emission on the graphene surface.The localized plasmons generated from the plasmonic nanostructures of shell-isolated nanoparticle coupling to ultra-flat Au substrate would dictate a consistent junction geometry while enhancing the optical field and dominating the electron transition pathways,which may cause obvious perturbations for molecular radiation behaviors.Additionally,the three-dimensional finite-difference time-domain and time-dependent density functional theory were also carried out to simulate the distributions of electromagnetic field and energy levels of hybrid nanostructure respectively and the results agreed well with the experimental data.Therefore,this work paves a novel approach for tunning graphene charge/energy transfer processes,which may hold great potential for applications in photonic devices based on graphene.

Converting CO_(2)to ethanol on Ag nanowires with high selectivity investigated by operando Raman spectroscopy

Electrochemical conversion of CO_(2)into liquid fuels provides an efficient way to store the renewable energy in the production of fuels and chemicals.However,effectively converting CO_(2)to ethanol remains extremely challenging due to the low activity and selectivity.Herein,we achieve a high ethanol Faradaic efficiency(FE)as high as 85%on Ag nanowires(NWs)for CO_(2)electroreduction at-0.95 V.X-ray photoelectron spectroscopy and electrochemical experiments prove that such Ag NWs are partially oxidized.Operando Raman spectroscopy finds the important CO intermediate adsorbed on partially oxidized Ag NWs,facilitating the ethanol formation.Density functional theory calculations prove that the reaction energy of CO coupling with the*CHO to*COCHO intermediate on the partially oxidized Ag NWs is smaller than that on the surface of Cu,which explains why the ethanol FE of such partially oxidized Ag NWs can exceed that of Cu,and therefore is the most favorable pathway for the formation of C_(2)products on partially oxidized Ag NWs.This study provides a new insight to design efficient catalysts and investigate the mechanisms to improve the selectivity.