In a significant advancement for electrochemical research, a new technique known as in situ electrochemical surface-enhanced Raman spectroscopy (EC-SERS) has been developed to identify interfacial species in real-time. This method amplifies Raman signals using plasmonic nanostructures, allowing researchers to capture the vibrational signals of trace and transient species under operational conditions. The findings were published in the journal eScience in March 2025, offering a groundbreaking understanding of reaction mechanisms in electrocatalysis.
The review details how EC-SERS can track the dynamic evolution of Raman peaks related to interfacial species. By doing so, it reveals the influence of electrocatalyst properties and interfacial environments on reactions pertinent to fuel cells, water electrolysis, and CO2 reduction. This technique establishes direct correlations between interfacial species, reaction pathways, and mechanisms, providing critical insights for designing more efficient electrocatalysts and electric double layers (EDLs) aimed at sustainable energy solutions.
Researchers from various institutions highlighted the principles, substrate-engineering strategies, and experimental designs that facilitate the coupling of Raman enhancement with electrochemical control. The study emphasizes how EC-SERS can identify various intermediates and surface states of electrocatalysts, as well as their interactions in systems involving hydrogen, oxygen, and CO2 conversions. This molecular-level perspective enhances the interpretation of reaction pathways and mechanisms during operational conditions.
The authors describe how localized surface plasmon resonance (LSPR) on gold (Au), silver (Ag), and copper (Cu) nanostructures generates intense electromagnetic “hotspots.” These hotspots significantly amplify Raman signals, enabling the detection of species at monolayer levels. The review also summarizes effective strategies for constructing SERS substrates, including electrochemical roughening and core-shell nanoparticles, which are essential for electrocatalysts that do not possess intrinsic Raman activity.
By employing techniques such as potential-dependent Raman shifts and vibrational Stark effects, EC-SERS can distinguish key intermediates like H*, OH*, OOH*, and surface oxides. Case studies illustrate its capabilities, including differentiating between associative and dissociative oxygen-reduction pathways on platinum (Pt) single crystals and revealing kinetics related to hydrogen evolution on ruthenium (Ru) surfaces.
This innovative technique also offers insights into the structural evolution of interfacial water, investigating its hydrogen-bond network and orientation. By integrating EC-SERS with density functional theory (DFT) and ab initio molecular dynamics (AIMD) simulations, the study correlates vibrational frequencies with adsorption energies and reaction barriers. This establishes a direct link between electronic properties and electrocatalytic performance across various clean-energy reactions.
The authors assert that EC-SERS provides “molecular-level clarity that was previously unattainable in operando electrocatalysis.” They emphasize that subtle shifts in vibrational modes can track surface reorganizations, the appearance or disappearance of reaction intermediates, and the modulation of electron-proton transfer by interfacial water and cations. This visualization capability under working conditions positions EC-SERS as a vital link between spectroscopy and theoretical models.
Looking ahead, the authors discuss potential developments that could enhance the utility of EC-SERS, such as broader potential windows, multimodal spectroscopic integration, improved spatial resolution, and machine-learning-assisted spectral interpretation. These advancements could establish EC-SERS as a standard diagnostic tool for operando catalysis, accelerating the development of high-efficiency, durable energy-conversion systems essential for a low-carbon future.
The comprehensive review also acknowledges the funding support received from the National Natural Science Foundation of China and other institutions, underscoring the collaborative effort behind this pioneering work. The full article can be accessed through the DOI: 10.1016/j.esci.2024.100352, providing valuable insights for researchers and practitioners in the field of electrochemistry and sustainable energy technologies.
