Direct identification of the carbonate intermediate during water-gas shift reaction at Pt-NiO interfaces using surface-enhanced Raman spectroscopy

Noble metal-reducible oxide interfaces have been regarded as one of the most active sites for water-gas shift reaction.However,the molecular reaction mechanism of water-gas shift reaction at these interfaces still remains unclear.Herein,water-gas shift reaction at Pt-NiO interfaces has been in-situ explored using surface-enhanced Raman spectroscopy by construction of Au@Pt@NiO nanostructures.Direct Raman spectroscopic evidence demonstrates that water-gas shift reaction at Pt-NiO interfaces proceeds via an associative mechanism with the carbonate species as a key intermediate.The carbonate species is generated through the reaction of adsorbed CO with gaseous water,and its decomposition is a slow step in water-gas shift reaction.Moreover,the Pt-NiO interfaces would promote the formation of this carbonate intermediate,thus leading to a higher activity compared with pure Pt.This spectral information deepens the fundamental understanding of the reaction mechanism of water-gas shift reaction,which would promote the design of more efficient catalysts.

In situ tracking of the lithiation and sodiation process of disodium terephthalate as anodes for rechargeable batteries by Raman spectroscopy

Organic compounds represent an appealing group of electrode materials for rechargeable batteries due to their merits of biomass,sustainability,environmental friendliness,and processability.Disodium terephthalate(Na_(2)C_(8)H_(4)O_(4),Na_(2)TP),an organic salt with a theoretical capacity of 255 mAh·g^(-1),is electroactive towards both lithium and sodium.However,its electrochemical energy storage(EES)process has not been directly observed via in situ characterization techniques and the underlying mechanisms are still under debate.Herein,in situ Raman spectroscopy was employed to track the de/lithiation and de/sodiation processes of Na2TP.The appearance and then disappearance of the–COOLi Raman band at 1625 cm^(-1) during the de/lithiation,and the increase and then decrease of the–COONa Raman band at 1615 cm^(-1) during the de/sodiation processes of Na2TP elucidate the one-step with the 2Li+or 2Na+transfer mechanism.We also found that the inferior cycling stability of Na2TP as an anode for sodium-ion batteries(SIBs)than lithium-ion batteries(LIBs)could be due to the larger ion radium of Na+than Li+,which results in larger steric resistance and polarization during EES.The Na2TP,therefore,shows greater changes in spectra during de/sodiation than de/lithiation.We expect that our findings could provide a reference for the rational design of organic compounds for EES.

In situ Raman,FTIR,and XRD spectroscopic studies in fuel cells and rechargeable batteries

As state-of-the-art electrochemical energy conversion and storage(EECS)techniques,fuel cells and rechargeable batteries have achieved great success in the past decades.However,modern societies’ever-growing demand in energy calls for EECS devices with high efficiency and enhanced performance,which mainly rely on the rational design of catalysts,electrode materials,and electrode/electrolyte interfaces in EESC,based on in-deep and comprehensive mechanistic understanding of the relevant electrochemical redox reactions.Such an understanding can be realized by monitoring the dynamic redox reaction processes under realistic operation conditions using in situ techniques,such as in situ Raman,Fourier transform infrared(FTIR),and X-ray diffraction(XRD)spectroscopy.These techniques can provide characteristic spectroscopic information of molecules and/or crystals,which are sensitive to structure/phase changes resulted from different electrochemical working conditions,hence allowing for intermediates identification and mechanisms understanding.This review described and summarized recent progress in the in situ studies of fuel cells and rechargeable batteries via Raman,FTIR,and XRD spectroscopy.The applications of these in situ techniques on typical electrocatalytic electrooxidation reaction and oxygen reduction reaction(ORR)in fuel cells,on representative high capacity and/or resource abundance cathodes and anodes,and on the solid electrolyte interface(SEI)in rechargeable batteries are discussed.We discuss how these techniques promote the development of novel EECS systems and highlight their critical importance in future EECS research.

Manipulating the light-matter interactions in plasmonic nanocavities at 1 nm spatial resolution

The light-matter interaction between plasmonic nanocavity and exciton at the sub-diffraction limit is a central research field in nanophotonics.Here,we demonstrated the vertical distribution of the light-matter interactions at~1 nm spatial resolution by coupling A excitons of MoS2 and gap-mode plasmonic nanocavities.Moreover,we observed the significant photoluminescence(PL)enhancement factor reaching up to 2800 times,which is attributed to the Purcell effect and large local density of states in gap-mode plasmonic nanocavities.Meanwhile,the theoretical calculations are well reproduced and support the experimental results.

Plasmonic photocatalysis:Mechanism,applications and perspectives

The process of photocatalysis,regarded as a promising approach for tackling the energy crisis and environmental pollution issues,is crucial for turning solar light into chemical resources.However,the solar-chemical conversion efficiency of typical semiconductor catalysts is still too low,so it is vital to figure out how to boost photocatalytic performance of semiconductors.Under visible light illumination,the local surface plasmon resonance(LSPR)induced by coinage metal would enhance the local electric field and improve photocatalytic performance of semiconductors,especially in the visible range.Therefore,its attachment to semiconductors has been regarded as an efficient strategy to improve photocatalytic performance.This paper reviews the latest research progress of plasmonic photocatalysis from theory to application.Starting from the excitation and relaxation of plasmons,four main mechanisms of plasmon-enhanced semiconductor photocatalysis are introduced,including enhanced light absorption and scattering,local electromagnetic field enhancement,improved hot carriers(HCs)injection and enhanced thermal effect.Secondly,the current mainstream plasmonic photocatalysts,such as monometallic,bimetallic and non-noble metal-based plasmonic catalysts,are reviewed.Finally,the applications of plasmonic photocatalysts in H_(2) production,CO_(2) reduction,and antibacterial are further summarized.

Plasmonic Core−Shell Materials:Synthesis,SpectroscopicCharacterization,and Photocatalytic Applications

CONSPECTUS:The ability to concentrate light at the nanoscale and produce extremely high local electromagnetic(EM)fields makes plasmonics a promising and rapidly developing research area.In the region with high EM field intensity(usually called the“hot spot”),various processes can be significantly enhanced,including spectroscopy,luminescence,catalysis,etc.However,only coinage metals(material limitation)with nanoscale roughness(morphological limitation)exhibit significant plasmonic effects under the visible light region,which greatly hinders wider and further applications of plasmonics.Constructing plasmonic core−shell materials by coating a second material onto the surface of a plasmonic metal core is a potential solution to these limitations.The plasmonic core can amplify the signals and/or accelerate the processes of the shell materials or other substrates of interest,making plasmonic research on nonplasmonic materials possible,thus expanding the applications of plasmonics.Besides,through controllable synthesis,the size and composition of both the core and the shell can be tuned simultaneously and precisely.This offers huge possibilities to study and tune plasmonic structure−performance effects at the(sub)nanometer level,which would otherwise not be feasible.