Instantly Detecting Catalysts’ Hot Spots Temperature In Situ during Photocatalysis by Operando Raman Spectroscopy

Abstract

Precisely detecting the catalysts' hot spots temperature in situ instantly during photocatalysis is a great challenge but extremely important for chemical reactions. However, no efficient method has been developed to instantly detect the hot spots temperature in situ during photocatalysis. Herein, we designed a simple and convenient method to measure the instant hot spots temperature in situ on the nanostructure surface during photocatalysis by operando Raman spectroscopy using 4-methoxyphenyl isocyanide (MI) as the probe molecule. The ν NC frequency of MI varied linearly with temperature, which is caused by the orientation change of the MI induced by temperature, leading to the change in the frequency of the ν NC bond that directly interacts with the nanostructure surface. Using in situ surface-enhanced Raman spectroscopy (SERS), the surface temperature of the catalysts illuminating for each time can be measured instantly. Interestingly, the catalytic activity of the hydrogen evolution reaction (HER) for the Au−Ag/Ag 2 S heterojunction nanorods (HJNRs) are higher than that for the Ag−Au−Ag HJNRs, although they have a lower surface temperature during photocatalysis; therefore, hot carriers and electronic structure contributed more to the catalytic activity of the Au−Ag/Ag 2 S HJNRs than that of the Ag−Au−Ag HJNRs. Such an instant hot spots temperature detecting method of catalysts can greatly facilitate the analysis of the mechanism of catalytic processes.

Self-Referenced SERS Thermometry of Molecules on a Metallic Nanostructure

“…The anti-Stokes continuum spectrum ,− of a plasmon-excited metal nanostructure can offer the electronic temperature of the metal. The temperature dependences of the fluorescence ,, of dyes close to the nanostructure and the peak shifts , or intensity changes , of the surface-enhanced Raman scattering (SERS) spectra of some adsorbates can provide the local temperatures of molecules. These molecular thermometry techniques rely on probe-specific spectral responses to the temperature changes, requiring a careful selection of probes and full temperature–spectrum calibrations for each probe.…”

Exploring the Effect of Pd on the Oxygen Reduction Performance of Pt by In Situ Raman Spectroscopy

“…As one of the high-efficiency, high-reliability, and environment-friendly energy conversion technologies, fuel cells are promising to reduce the dependence on traditional fossil fuels to solve the global environmental problems. − However, the practical application and development of the fuel cells are hindered by the sluggish kinetics of oxygen reduction reaction (ORR), which is the most critical cathode reaction in fuel cells . Platinum (Pt) and Pt-based compounds are considered as the state-of-the-art electrocatalysts for ORR in the past decades, − but their widespread implementation is still severely restricted by the high cost and reserve scarcity.…”

Studying the Generation of Hot Electrons in Plasmonic Nanoparticle Monolayers

“…The compound 4-methoxyphenyl isocyanide (4-MI) is used to probe the temperature on the NPs surface. 49 The NP surface temperature is probed using 4-MI and SERS. The 4-MI molecule attaches to the NP's surface through the carbon atom in the isocyanide (νC≡N) functional group, the chemical structure of 4-MI can be observed in Figure 23.…”

“…The 4-MI molecule attaches to the NP's surface through the carbon atom in the isocyanide (νC≡N) functional group, the chemical structure of 4-MI can be observed in Figure 23. 49,50 Figure 23: Chemical structure of 4-MI, the molecule attaches to a metal NP's surface through the carbon atom in the isocyanide functional group. The chemical structure of 4-MI was made using the online ChemDraw program.…”

“…50 The SERS spectra of 4-MI on AuAg nanorods can be observed in Figure 24, a SERS spectrum was obtained for a range of temperatures (20 0 C -100 0 C) using an external temperature controlled apparatus. 49 In the SERS spectra, the peak associated with the isocyanide functional group appears around 2188 cm -1 at 20 0 C, the peak shifted to 2172 cm -1 when the temperature was increased to 100 0 C. 49 A calibration curve can be constructed using the wavenumber values of the isocyanide peak at each temperature, Figure 24. 49 With the calibration curve constructed, the experiment could be run without the external temperature apparatus; then, the position of the isocyanide peak in the SERS spectra can give an indication of the NPs surface temperature.…”