Electrochemical Raman Spectroscopy Research Articles

Dual confinement of RuOx nanoparticle using polar MnNiO and armored carbon for boosting water electrolysis

The poor stability of nanoparticle catalysts with catalytic activity is a significant obstacle to their industrial application. The establishment of rational nanoparticle structures to elucidate the relationship between catalyst structure and its catalytic activity and stability is crucial for constructing nanoparticle catalysts that are both highly active and stable. We propose a strategy to construct a dual-confinement effect of the nanoparticle, specifically by regulating the polarization of the MnNiO support to enhance strong oxide-support interactions (SOSI) and encapsulating the outer layer of nanoparticles with a carbon shell, which has been proven effective in improving the activity and stability of nanoparticle-based oxygen evolution reaction (OER) electrocatalysts. At a current density of 100 mA cm−2, the armor C@RuOx@MnNiO catalyst displays an overpotential of 260 mV for the OER. After the OER test for 100 h, the current density of C@RuOx@MnNiO shows no significant decay, whereas that of RuOx@MnNiO and RuOx@MnO rapidly decreases, indicating significant catalytic activity and stability of the catalyst. The assembled C@RuOx@MnNiO||Pt/C electrode demonstrates excellent alkaline water electrolysis performance in an MEA electrolyzer, requiring only a low cell voltage of 1.76 V to achieve an ampere-level current density of 1 A cm−2. In-situ electrochemical Raman spectroscopy reveals the significant interaction between nanoparticles and the polar support. The reduction in Gibbs free energy, which establishes the rate-determining step (RDS) of OER, is caused by the charge redistribution caused by polar Mn doping in RuOx@MnNiO and the coordination structure modifications, as shown by density functional theory calculations. This work provides an approach to designing efficient and stable nanoparticle electrocatalysts through the dual-confinement effect of SOSI-induced strong interactions and armor carbon layers.

Operando characterization of Cr-containing alloy passivation film by synchrotron radiation

Techniques of electrochemical-spectroscopic ellipsometry, electrochemical-Raman spectroscopy, and electrochemical-grazing incidence X-ray diffraction using the electrochemical synchrotron radiation source were combined to characterize the growth process of chromium-containing passivation film. The operando method can characterize passivation film in detail and monitor the growth process of these films, which can not be done sufficiently using uncombined traditional structural characterization techniques. For example, Fe-18 wt%Cr steel was used to monitor the passivation process, such as adsorbed species that transformed into stable species and the decrease in the dissolution of internal metals. This means that the operando method developed in this work could effectively monitor passivation.

Asymmetric Coordination Regulating D‐Orbital Spin‐Electron Filling in Single‐Atom Iron Catalyst for Efficient Oxygen Reduction

AbstractThe single‐atom Fe−N−C catalyst has shown great promise for the oxygen reduction reaction (ORR), yet the intrinsic activity is not satisfactory. There is a pressing need to gain a deeper understanding of the charge configuration of the Fe−N−C catalyst and to develop rational modulation strategies. Herein, we have prepared a single‐atom Fe catalyst with the co‐coordination of N and O (denoted as Fe−N/O−C) and adjacent defect, proposing a strategy to optimize the d‐orbital spin‐electron filling of Fe sites by fine‐tuning the first coordination shell. The Fe−N/O−C exhibits significantly better ORR activity compared to its Fe−N−C counterpart and commercial Pt/C, with a much more positive half‐wave potential (0.927 V) and higher kinetic current density. Moreover, using the Fe−N/O−C catalyst, the Zn‐air battery and proton exchange membrane fuel cell achieve peak power densities of up to 490 and 1179 mW cm−2, respectively. Theoretical studies and in situ electrochemical Raman spectroscopy reveal that Fe−N/O−C undergoes charge redistribution and negative shifting of the d‐band center compared to Fe−N−C, thus optimizing the adsorption free energy of ORR intermediates. This work demonstrates the feasibility of introducing an asymmetric first coordination shell for single‐atom catalysts and provides a new optimization direction for their practical application.

Asymmetric Coordination Regulating D-Orbital Spin-Electron Filling in Single-Atom Iron Catalyst for Efficient Oxygen Reduction.

The single-atom Fe-N-C catalyst has shown great promise for the oxygen reduction reaction (ORR), yet the intrinsic activity is not satisfactory. There is a pressing need to gain a deeper understanding of the charge configuration of the Fe-N-C catalyst and to develop rational modulation strategies. Herein, we have prepared a single-atom Fe catalyst with the co-coordination of N and O (denoted as Fe-N/O-C) and adjacent defect, proposing a strategy to optimize the d-orbital spin-electron filling of Fe sites by fine-tuning the first coordination shell. The Fe-N/O-C exhibits significantly better ORR activity compared to its Fe-N-C counterpart and commercial Pt/C, with a much more positive half-wave potential (0.927 V) and higher kinetic current density. Moreover, using the Fe-N/O-C catalyst, the Zn-air battery and proton exchange membrane fuel cell achieve peak power densities of up to 490 and 1179 mW cm-2, respectively. Theoretical studies and in situ electrochemical Raman spectroscopy reveal that Fe-N/O-C undergoes charge redistribution and negative shifting of the d-band center compared to Fe-N-C, thus optimizing the adsorption free energy of ORR intermediates. This work demonstrates the feasibility of introducing an asymmetric first coordination shell for single-atom catalysts and provides a new optimization direction for their practical application.

Ligand-Induced Electronic Structure Modulation of Self-Evolved Ni3S2 Nanosheets for the Electrocatalytic Oxygen Evolution Reaction.

Modulating the electronic structure of the electrocatalyst plays a vital role in boosting the electrocatalytic performance of the oxygen evolution reaction (OER). In this work, we introduced a one-step solvothermal method to fabricate 1,1-ferrocene dicarboxylic acid (FcDA)-decorated self-evolved nickel sulfide (Ni3S2) nanosheet arrays on a nickel foam (NF) framework (denoted as FcDA-Ni3S2/NF). Benefiting from the interconnected ultrathin nanosheet architecture, ligand dopants induced and facilitated in situ structural reconstruction, and the FcDA-decorated Ni3S2 (FcDA-Ni3S2/NF) outperformed its singly doped and undoped counterparts in terms of OER activity. The optimized FcDA-Ni3S2/NF self-supported electrode presents a remarkably low overpotential of 268 mV to achieve a current density of 10 mA cm-2 for the OER and demonstrates robust electrochemical stability for 48 h in a 1.0 M KOH electrolyte. More importantly, in situ electrochemical Raman spectroscopy reveals the generation of catalytically active oxyhydroxide species (NiOOH) derived from the surface construction during the OER of pristine FcDA-Ni3S2/NF, contributing significantly to its superior electrocatalytic performance. This study concerns the modulation of electronic structure through ligand engineering and may provide profound insight into the design of cost-efficient OER electrocatalysts.

Unleashing Ultrahigh Capacity and Lasting Stability: Aqueous Zinc‐Sulfur Batteries

AbstractDespite of multifarious dominance of sulfur‐based batteries, polysulfide‐shuttling and use of high‐cost organic electrolytes with flammability risks hinder their applicability as commercial devices. Herein a polysulfide‐free aqueous zinc‐sulfur (Zn─S) rechargeable battery is explored, which offers a low‐cost and environmentally friendly energy storage system being Zn and Sulfur (S) highly abundant with high theoretical capacity. However, the stability of Zn anode is quite challenging due to dendritic growth and corrosion leading to the capacity decay. This work showcases the utilization of ethylene glycol (EG) and iodine (I2) as an electrolyte additive in aqueous zinc acetate [Zn(OAc)2] electrolyte for stabilizing the Zn─S battery performance. EG as an additive is able to mitigate the corrosion rate of the Zn electrode by 15 times which is supported by molecular dynamics simulation. The assembled Zn─S battery delivered an outstanding capacity of 1210 mA h g−1 at 0.1 C with a 91% capacity retention even after 250 cycles, along with remarkable reversible prolonged cycling stability of 3000 cycles at 1 C, with 64.5% capacity retention. More importantly, in situ electrochemical Raman spectroscopy is utilized to monitor the real‐time formation of zinc sulfide (ZnS) as a single discharge product and simultaneously debunking the polysulfide shuttling in the system which is further supported by XPS, UV‐Vis and IR spectroscopy.

Enhancing Hydrogen Evolution Catalysis through Potential-Induced Structural Phase Transition in Transition-Metal Dichalcogenide Thin Sheets.

Enhancing electrocatalytic performance relies on effective phase control, which influences key catalytic properties, such as chemical stability and electrical conductivity. Traditional methods for manipulating the phase of transition-metal dichalcogenides (TMDs), including high-temperature synthesis, Li intercalation, and doping, involve harsh conditions and energy-intensive processes. This study introduces an innovative approach to crafting heterophase structures (2H-1T-WS2) in TMDs, using WS2 as a model compound, encompassing both semiconducting (2H) and metallic (1T) types through a straightforward potential activation method. Insights from in situ electrochemical Raman spectroscopy, HR-TEM, and XPS measurements reveal distinctive partial phase-transition behavior. This behavior enables the partially exposed basal plane of 2H-1T-WS2 to demonstrate superior activity in the hydrogen evolution reaction (HER), attributed to enhanced electrical conductivity and the exposure of highly active sites. The potential-induced phase transition presents promising avenues for the development of catalysts with heterophase structures.

ALD-Engineered CuxO Overlayers Transform ZnO Nanorods for Selective Production of CO in Electrochemical CO2 Reduction.

The electrochemical CO2 reduction reaction (CO2RR) holds tremendous promise as a strategy for lowering atmospheric CO2 levels and creating new clean energy sources. The conversion of CO2RR to CO, in particular, has garnered significant scientific interest due to its industrial feasibility. Within this context, the CuZn-based electrocatalyst presents an attractive alternative to conventional CO-selective electrocatalysts, which are often costly and scarce. Nevertheless, the wide-range utilization of CuZn electrocatalysts requires a more comprehensive understanding of their performance and characteristics. In this study, we synthesized ZnO nanorods through electrodeposition and subsequently coated them with CuxO overlayers prepared by atomic layer deposition (ALD). CuxO significantly enhanced CO selectivity, and 88% CO selectivity at a relatively low potential of -0.8 V was obtained on an optimized CuxO overlayer thickness (CuxO-250/ZnO). The addition of CuxO on ZnO was found to dramatically increase the electrochemical surface area (ESCA), lower the charge-transfer resistance (Rct), and introduce new active sites in the ε-CuZn4 phase. Furthermore, electrochemical Raman spectroscopy results showed that the CuxO-250/ALD electrode developed a ZnO layer on the surface during the CO2RR, while the bare ZnO electrode showed no evidence of ZnO during the reaction. These results suggest that the addition of CuxO by ALD played a crucial role in stabilizing ZnO on the surface. The initial amount of CuxO was shown to further affect the redeposition of the ZnO layer and hence affect the final composition of the surface. We attribute the improvement in CO selectivity to the introduction of both ε-CuZn4 and ZnO that developed during the CO2RR. Overall, our study provides new insights into the dynamic behavior and surface composition of CuZn electrocatalysts during CO2RR.

Direct Electroreduction of Carbonate to Formate

A cause of losses in energy and carbon conversion efficiencies during the electrochemical CO2 reduction reaction (eCO2RR) can be attributed to the formation of carbonates (CO3 2–), which is generally considered to be an electrochemically-inert species. Herein, we employ in-situ electrochemical Raman spectroscopy, liquid chromatography, nuclear magnetic resonance spectroscopy, 13C isotope-labelling and density functional theory (DFT) simulations to understand the role of carbonate species formed on copper catalysts during eCO2RR, and its ability to reduce to formate. Direct carbonate-to-formate conversion was confirmed by the the direct reduction of CuCO3, and by pulse reduction of N2-saturated K2CO3 electrolyte on Cu,. DFT simulations elucidated the nature of the active sites generating the Cu-CO3 2– species and revealed the mechanism for the pulse-enabled carbonate reduction to formate. Combining both experimental and computational results, we proposed that a dynamic carbonate intermediate was constantly formed on Cu during eCO2RR, that further evolves to formate between –0.4 to –1.2 VRHE on Cu. Control systems using Pb, Ag and Au electrodes were also studied.

In Situ Electrochemical Raman Spectroscopy of MXenes in Confined Electrolytes

MXenes, a large family of two-dimensional materials, have attracted interest due to their large chemistry space and diverse chemical, electrical, mechanical, and optical properties. MXenes follow the general formula Mn+1XnT x (n = 1-4) with M representing an early transition metal, X—carbon and/or nitrogen, and T—surface terminations (=O, –OH, and –F). In particular, MXenes’ metallic conductivities and redox-active surfaces make them attractive for electrochemical energy storage. Like with many other 2D materials, Raman spectroscopy has proven to be a crucial tool for MXene characterization. More recently, in situ Raman was used to elucidate structural changes in MXene electrodes during electrochemical cycling with a subset of aqueous electrolytes. Confined electrolytes (water-in-salt, PEG, etc.) have shown promise in various electrochemical systems, with recent results pointing to new charge storage mechanisms in MXenes. Further exploration is needed to understand the effect of the cations, anions, and concentrations of confined electrolytes on charge storage mechanisms. This work focuses on using in situ electrochemical Raman spectroscopy to analyze different confined electrolyte systems in MXene cells. The findings demonstrate the potential of using MXenes in aqueous electrochemical devices.

Dual‐laser pulse‐patterned α‐Co(OH)2/rGO heterointerface for accelerated water oxidation and surface phase‐transition via in‐situ Raman spectroscopy

AbstractThe dynamic surface reconstruction of electrodes is a legible sign to understand the deep phase‐transition mechanistic and electrocatalytic origin during the oxygen evolution reaction (OER). Herein, we report a dual‐laser pulse‐patterned heterointerface of α‐Co(OH)2 and reduced graphene oxide (rGO) nanosheets via pulsed laser irradiation in liquid (PLIL) to accelerate OER kinetics. α‐Co(OH)2 was formed from the OH− ions generated during the PLIL of GO at neutral pH. Co2+ modulation in tetrahedral coordination sites benefits as an electrophilic surface for water oxidation. Few d‐vacancies in Co2+ increase its affinity toward oxygen, lowering the energy barrier and generating many CoOOH and CoO2 active sites. rGO with an ordered π‐conjugated system aids the surface adsorption of OOH*, O*, and OH* during OER. α‐Co(OH)2 surface phase‐transition and OER mechanistic steps occurred via phase‐reconstruction to CoOOH and CoO2 reactive intermediates, uncovered using in situ electrochemical–Raman spectroscopy. Our findings in the dual‐laser pulse strategy and the surface reconstruction correlation in active OER catalysts pave the path for paramount in multiple energy technologies.image

Electric-Field-Induced Assembly of an Ionic Liquid-Water Interphase Enables Efficient Heavy Metal Electrosorption.

Controlling ion desolvation, transport, and charge transfer at the electrode-electrolyte interface (EEI) is critical to enable the rational design of the efficient and selective separation of targeted heavy metals and the decontamination of industrial wastewater. The main challenge is to sufficiently resolve and interrogate the desolvation of solvated metal ions and their subsequent electroreduction at the EEI and establish pathways to modulate these intermediate steps to achieve efficient energy transfer for targeted reactive separations. Herein, we obtained a predictive understanding of modulating the desolvation and electrosorption of Pb2+ cations using the hydrophobic ionic liquid 1-ethyl-3-methylimidazolium chloride (EMIMCl) in aqueous electrolyte. We revealed the formation of a compact interphase layer consisting of EMIMCl-Pb complexes under an applied electric field using operando electrochemical Raman spectroscopy, atomic force microscopy, and electrochemical impedance spectroscopy measurements combined with classical molecular dynamics simulations. A lower negative potential was shown to result in the formation of a well-oriented layer with the positive imidazolium ring of EMIMCl lying perpendicular to the electrode and the hydrophobic alkyl chain extending into the bulk electrolyte. This oriented layer, which formed from a dilute concentration of EMIMCl added to the electrolyte, was demonstrated to facilitate desolvation of incoming solvated Pb2+ cations and decrease the charge transfer resistance for Pb electrodeposition, which has important implications for the selective removal of Pb from contaminated mixtures. Overall, our findings open up new opportunities to modulate ion desolvation using hydrophobic ionic liquids in aqueous electrolytes for efficient heavy-metal separation.

Highly dispersed copper-iron nanoalloy enhanced electrocatalytic reduction coupled with plasma oxidation for ammonia synthesis from ubiquitous air and water

Conversion of nitrogen to ammonia at ambient conditions is a promising avenue for future distributed energy storage and fertilizer supply. However, it is currently hindered by the difficult nitrogen activation and competitive hydrogen evolution reaction. Herein, we develop a new strategy of highly dispersed copper-iron (Cu-Fe) nanoalloy enhanced electrocatalytic nitrate reduction to ammonia (NRA), in which nitrate can be derived from nitrogen and oxygen in the air via plasma process. The nitrate obtained by plasma oxidation of air is more than 3 times as much as nitrite, and the total yield rate of nitrate and nitrite is over 137 μmol·h1 by a single electrode of Tesla coil. Highly dispersed Cu-Fe nanoalloy with different ratios of Cu to Fe were prepared for NRA catalysts using the Joule heating method with instantaneous thermal shock, Cu10Fe1 nanoalloy demonstrates the best NRA activity, exhibits an excellent ammonia yield rate of 190.46 μmol·h1·cm2 and Faraday efficiency of 93.74 %. The Kelvin probe force microscope, in situ electrochemical Raman spectroscopy and density functional theory reveal the enhancing effect and tuning mechanism of Fe atom on the adsorption energy and electronic structure of Cu. This work opens up a new pathway for ammonia synthesis from air and water and provides a new strategy for the construction of high-performance NRA catalysts and the analysis of the reaction mechanism.

Highly Localized Charges of Confined Electrical Double‐Layers Inside 0.7‐nm Layered Channels

AbstractA confined electrical double‐layer (EDL) inside nanoporous electrodes has a large capacitance and deviates from traditional ones. Unfortunately, its capacitive mechanism is still unclear. Herein, expanded vertical graphene/diamond (EVG/D) films with regular and ordered 0.7‐nm layered channels are designed and synthesized to serve as an ideal model for understanding confined EDL. A clear overall picture of confined EDL is provided at an atomic resolution with the aid of in situ electrochemical Raman spectroscopy, electrochemical quartz crystal microbalance (EQCM), and density functional theory (DFT) calculations combined with three‐dimension reference interaction site method (3D‐RISM). It is especially interesting that the induced charges in electrode hosts are highly localized with a density far higher than that on a traditional EDL and even close to those of ion batteries. It is proposed that such a high localization of induced charges plays an essential role in the high energy storage efficiency of confined EDL capacitance. This work not only provides a previously unexplored way to refine the mechanism of confined EDL, but also further lays the foundation for understanding the functions of nanoporous or layered materials in electrochemical energy storage.

Selective electrocatalytic reforming of PET-derived ethylene glycol to formate with a Faraday efficiency of 93.2% at industrial-level current densities

The accumulation of plastic waste results in severe environmental pollution and enormous losses of valuable resources, and thus recycling plastic waste has become an urgent scientific and social challenge. Herein, we report the electrocatalytic reforming of polyethylene terephthalate (PET)-derived ethylene glycol (EG) to formate by using a Ni(OH)2/Ni foam catalyst, which exhibits > 90% Faraday efficiency and selectivity even at industrially relevant current densities (>500 mA cm-2 at 1.60 V vs RHE). In-situ electrochemical Raman spectroscopy reveals that NiOOH can be swiftly formed at a relatively low potential in the presence of EG and plays a crucial role toward PET-derived EG oxidation. The massive production of NiOOH leads to a large potential gap of 430 mV at 100 mA cm-2 compared to the oxygen evolution reaction (OER), hence improving the Faraday efficiency of EGOR. This work highlights the promising potential of electrocatalytic reforming of PET for practical applications.

The Guest Doping Effects of Fe on Bimetallic NiCo Layered Double Hydroxide for Enhanced Electrochemical Oxygen Evolution Reaction: Theoretical Screening and Experimental Verification

AbstractExploring efficient transition‐metal‐based electrocatalysts for oxygen evolution reaction (OER) is imperative but remain challenging for sustainable energy storage and conversion systems. Foreign species doping is a significant regulation strategy to enhance the intrinsic activity of host matrix. However, the potential relationship of structure‐activity caused by guest doping elements is seldom tracked systematically. In this case, both theoretical screening and experimental verification are complementarily employed to investigate the guest doping effects of ten first‐row transition metals (Sc∼Zn) on bimetallic NiCo layered double hydroxide (NiCo‐LDH). As a result, the optimized Fe‐doped NiCo‐LDH is identified as the most promising candidate toward alkaline electrocatalytic OER, which exhibits the quasi‐industrial current density of 1000 mA cm−2 at overpotential of 400 mV. Meanwhile, it also shows impressively long‐term stability of 500 h at 500 mA cm−2 with a negligible activity loss. Moreover, in situ electrochemical Raman spectroscopy unveils the dynamic structure evolution from pre‐catalytic state (Fe‐NiCo‐LDH) to metal oxyhydroxide (Fe‐(NiCo)OOH) during the oxidation reaction, and ab‐initio molecular dynamics simulations are further performed to confirm the thermodynamic stability of activated Fe‐(NiCo)OOH phase. This work provides a promising platform for exploring the critical role of transition metal guest doping on host matrix in developing industrially required OER electrocatalysts.

Reinforce the Co-O Covalency via Ce(4f)-O(2p)-Co(3d) Gradient Orbital Coupling for High-efficiency Oxygen Evolution.

Rare-earth (RE)-based transition metal oxides (TMO) are emerging as a frontier towards oxygen evolution reaction (OER), yet the knowledge regarding their electrocatalytic mechanism and active sites is very limited. Herein, we successfully design and synthesize atomically dispersed Ce on CoO by an effective plasma (P)-assisted strategy as a model (P-Ce SAs@CoO) to investigate the origin of OER performance in RE-TMO systems. The P-Ce SAs@CoO exhibits favorable performance with an overpotential of only 261mV at 10mA cm-2 and robust electrochemical stability, superior to individual CoO. X-ray absorption spectroscopy and in-situ electrochemical Raman spectroscopy uncover that the Ce-induced electron redistribution inhibits Co-O bond breakage in the Co-O-Ce unit site. Theoretical analyses demonstrate that the gradient orbital coupling reinforces the Co-O covalency of Ce(4f)-O(2p)-Co(3d) unit active site with an optimized Co-3d-eg occupancy, which can balance the adsorption strength of intermediates and in turn reach the apex of the theoretical OER maximum, in excellent agreement with experimental observations. We believe the establishment of this Ce-CoO model can set a basis for the mechanistic understanding and structural design of high-performance RE-TMO catalysts. This article is protected by copyright. All rights reserved.

Electrolysis of Glycerol by Non-Noble Metal Hydroxides and Oxides

A series of free-standing electrodes consisting of hydroxides (Ni(OH)2, Co(OH), NiFeLDH, and CoFeLDH) and oxides (NiO, Co3O4, NiFe2O4, and CoFe2O4) supported by carbon paper were fabricated via an in situ hydrothermal process and further examined for glycerol conversion. The morphology and structures of the samples were characterized by scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. The performance of the samples was studied by cyclic voltammetry, linear sweep voltammetry, and electrochemical impedance spectroscopy. The products of glycerol oxidation were analyzed by high-performance liquid chromatography. Operando electrochemical Raman spectroscopy was employed to monitor the variations on the active sites and intermediates. Among the samples, the NiO exhibited superior activity with the largest current density of 0.8 mA cm–2 at 1.7 V and selectivity of 97% for formic acid. Furthermore, coupling the hydrogen evolution reaction with the glycerol electro-oxidation reaction (GOR), we explored the electrolysis of water and glycerol. The potential of the electrolysis process was negatively shifted from 1.68 to 1.28 V by replacing the oxygen evolution reaction with GOR. The strategy reported in this work could afford a sustainable approach to produce hydrogen and value-added chemicals with high energy efficiency.

Impact of Highly Concentrated Alkaline Treatment on Mesostructured Cobalt Oxide for the Oxygen Evolution Reaction

AbstractCommercial alkaline water electrolysis cells typically use highly concentrate KOH as electrolyte, which strongly influences alteration of catalyst and its performance. Herein, the impact of alkaline treatment toward the structural alteration and electrochemical oxygen evolution reaction (OER) activity of well‐defined ordered mesoporous Co3O4 is systematically studied. The overall morphology of mesostructured Co3O4 is relatively resilient to the exposure of highly concentrated alkaline solution up to 13 m KOH. The spectroscopic analyses, including in situ diffuse reflectance infrared spectroscopy, reveal the presence of carbonate‐based species after the alkaline treatment due to impurities of the commercial KOH. The pre‐treated samples exhibit a higher electrochemically active surface area, decreased charge transfer resistance, and increased current density from 103 to 155 mA cm−2 at 1.7 V versus RHE. The in situ electrochemical Raman spectroscopy investigation supports formation of active CoOOH phase on KOH pre‐treated Co3O4, which might play a key role toward enhanced OER activity.

An experimental guide to in operando electrochemical Raman spectroscopy

Electrochemical Raman spectroscopy can provide valuable insights into electrochemical reaction mechanisms. However, it also shows various pitfalls and challenges. This paper gives an overview of the necessary theoretical background, crucial practical considerations for successful measurement, and guidance for in situ/in operando electrochemical Raman spectroscopy. Several parameters must be optimized for suitable reaction and measurement conditions. From the experimental side, considerations for the setup, suitable signal enhancement methods, choice of material, laser, and objective lens are discussed. Different interface phenomena are reviewed in the context of data interpretation and evaluation.Graphical