Infrared Absorption Research Articles

In Situ Surface-Enhanced Infrared Absorption Spectroscopy to Explore the Stability of Electrolyte in Nonaqueous Lithium Oxygen Batteries

Tetraethylene glycol dimethyl ether (TEGDME) decomposition on the Au electrode surface is studied using in situ attenuated total reflectance surface enhanced infrared absorption spectroscopy (ATR-SEIRAS). Due to the weak solvation of TEGDME, the superoxide intermediate (LiO2/O2−) of the discharge process rapidly gains electrons on the electrode surface to generate Li2O2. Furthermore, alkyl radical, formed by LiO2/O2− extracting hydrogen from ether, undergoes oxidative decomposition reactions to form by-products. During the charge process, amorphous film-like Li2O2 obtained from surface-phase mechanism oxidizes in the low potential range of 3–3.4 V, while the oxidation potential of large-sized crystal Li2O2 particles obtained from solution-phase mechanism is above 3.4 V. Besides, TEGDME is intrinsically unstable and can decompose at 3.8 V even the solution is saturated with argon, indicating that the degradation of ether-based electrolyte is inevitable during the cycling process. This work confirms the feasibility of ATR-SEIRAS in probing the reaction mechanism and electrolyte stability of lithium oxygen batteries, and provides direct spectroscopic evidence for subsequent optimization of electrolyte components.

External Cavity Quantum Cascade Laser Vibrational Circular Dichroism Spectroscopy for Fast and Sensitive Analysis of Proteins at Low Concentrations.

Proteins are characterized by their complex levels of structures, which in turn define their function. Understanding and evaluating these structures is therefore crucial to illuminating biological processes. One of the possible analytical methods is vibrational circular dichroism (VCD), which expands the structural sensitivity of classical infrared (IR) absorbance spectroscopy by the chiral sensitivity of circular dichroism. While this technique is powerful, it is plagued by low signal intensities and long measurement times. Here we present an optical setup leveraging the high brilliance of a quantum cascade laser to measure proteins in D2O at a path length of 204 μm. It was compared to classical Fourier-transform infrared spectroscopy (FT-IR) in terms of noise levels and in its applicability to secondary structure elucidation of proteins. Protein concentrations as low as 2 mg/mL were accessible by the laser-based system at a measurement time of 1 h. Further increase of the time resolution was possible by adapting the emission to cover only the amide I' band. This allowed for the collection of spectral data at a measurement time of 5 min without a loss of performance. With this high time resolution, we are confident that dynamic processes of protein can now be monitored by VCD, increasing our understanding of these reactions.

Excited State Dynamics of Geometrical Evolution of α-Substituted Dibenzoylmethanatoboron Difluoride Complex with Aggregation-Induced Emission Property.

Organic molecules with an aggregation-induced emission (AIE) property have been attracting much attention from the viewpoint of application to solid state emissive materials. For the AIE mechanism, quantum mechanical studies proposed the restriction of the intramolecular motion (RIM) model with the contribution of the conical intersection (CI) and deduced the importance of the restricted access to a conical intersection (RACI) in the potential energy surface (PES). Although these theoretical studies have contributed to the elucidation of AIE phenomena, direct detection of the reaction dynamics is indispensable to clarify the actual PES and the deactivation mechanism. Along this line, we investigated excited state dynamics of the AIE molecule with dibenzoylmethanatoboron difluoride complexes using time-resolved absorption spectroscopies in both visible and infrared (IR) regions. While the reference system of 1,3-bis(4-methoxyphenyl)methanatoboron difluoride (2aBF2) showed strong emission in solution, the methyl-substituted derivative at the α-position of the dioxaborine ring (2amBF2) led to the very weak fluorescence in solution but strong emission in the solid state. Time-resolved visible absorption measurements revealed a peak shift and broadening of the stimulated emission in the solution of 2amBF2, owing to the rapid change of the molecular geometry. With the temporal evolution of time-resolved IR absorption signals and density functional theory (DFT) calculation of these systems, it was deduced that 2amBF2 has two stable geometries, namely, planar and bending, in the S1 state and the bending geometry in the S1 state led to rapid conversion to the S0 state. These results support the RACI model in the aggregated states, leading to the AIE properties.

The Electrode/Electrolyte Interface Study during the Electrochemical CO2 Reduction in Acidic Electrolytes.

Electrochemical CO2 Reduction (CO2R) in acidic electrolytes has gained significant attention owing to higher carbon efficiency and stability than in alkaline counterparts. However, the proton source and the role of alkali cations for CO2R are still under debate. By using rotating ring disk electrode and surface-enhanced infrared absorption spectroscopy, we find that a neutral/alkaline environment at the interface is necessary for CO2R even in acidic electrolytes. We also confirm that water molecules, rather than protons serve as the proton source for CO2R. Alkali cations in the outer Helmholtz plane activate H2O and promote the desorption of adsorbed carbon monoxide. Additionally, the solvated CO2, or CO2(aq), is the actual reactant for CO2R. This study provides a deeper understanding of the electrode/electrolyte interface during CO2R in acidic electrolytes and sheds light on further performance improvement of this system.

Graphene/black phosphorus-based infrared metasurface absorbers with van der Waals Schottky junctions

Black phosphorus (BP) is a promising candidate for fabricating infrared (IR) photodetectors because its bandgap in the IR region can be controlled by varying the number of layers. BP-based metasurfaces have attracted considerable attention for applications in wavelength-selective and/or polarization-selective IR absorbers. Graphene and BP (Gr/BP) van der Waals (vdW) heterostructures are expected to enhance the performance of BP-based IR photodetectors. However, the Gr/BP vdW heterostructure forms a Schottky junction; thus, the electron transfer between Gr and BP should be investigated to determine the precise optical properties of Gr/BP vdW heterostructure-based metasurfaces. In this study, the electron transfer in the Gr/BP vdW heterostructure is investigated theoretically. The metasurface absorber structure proposed based on the results comprises periodic Gr/BP vdW heterostructure strips on top, a middle dielectric layer, and a bottom reflector. Numerical calculations indicated that the Gr/BP vdW heterostructure has strong wavelength- and polarization-selective near-unity IR absorption. The absorbance is increased and absorption wavelength is shortened compared with those of the monolayer-BP-based metasurface. The absorption wavelength can be controlled by changing the width of the Gr/BP strips owing to the hybrid localized surface plasmons of Gr/BP. This is attributed to the electron transfer through the Schottky junction between Gr and BP with enhanced localized surface plasmon resonance. The results suggest that the Gr/BP vdW heterostructure is a promising platform for realizing wavelength-selective and/or polarization-selective IR photodetectors and IR absorbers/emitters. The resulting photodetectors exhibit high responsivity and low noise because the BP bandgap corresponds to the IR wavelength region.

Theoretical and experimental study on the polarization-independent flanged nanowire array infrared absorber

An infrared (IR) absorber is a crucial component for thermal detectors, requiring high absorptance over a broad wavelength range while maintaining low heat capacity for optimal performance. Most thermal detectors use a thin film IR absorber that is suspended in air, supported by a layer beneath it for mechanical stability. However, this support layer increases heat capacity without contributing to IR absorptance, thereby reducing the performance of thermal detectors. In this paper, we introduce a polarization-independent nanowire array absorber using flanged nanowires with a C-shaped cross-section. This C-shaped design provides mechanical stability, eliminating the need for a support layer. Although nanowire array is generally known to exhibit polarization characteristics, the unique structure of the proposed flanged nanowires enables them to achieve polarization-independent properties, resulting in high absorptance similar to that of film absorbers. We theoretically analyzed the polarization-independent characteristics of the flanged nanowires using an optical circuit model and optimized the flanged nanowire structure using finite-difference time-domain (FDTD) simulations. Finally, we experimentally demonstrated the polarization-independent characteristics of the flanged nanowires and confirmed their high absorptance comparable to that of film absorbers.

High-Pressure Behaviors of Hydrogen Bonds in Fluorine-Doped Brucite.

Brucite, Mg(OH)2 (P3̅m1, Z = 1), is a prototype material for studying hydrogen bonds in solid hydroxides. In this study, substitutional effects of fluorine (F) on the hydrogen-bonding geometries of hydrogenated and deuterated brucite were investigated under ambient conditions and at high pressure using combined experimental methods of neutron powder diffraction, Raman spectroscopy, and infrared (IR) spectroscopy. Under ambient conditions, neutron powder diffraction results showed that F substitution decreased the donor-acceptor distance and increased the hydroxyl covalent bond lengths of both hydrogenated and deuterated brucite, strengthening the hydrogen bond. Red shifts of the hydroxyl stretching modes also indicated an elongation of d(O-H) and d(O-D). High-pressure neutron diffraction experiments were performed on Mg(OH)1.81F0.19 and Mg(OD)1.74F0.26 up to 7.04 and 10.02 GPa, respectively. For both samples, changes in the hydrogen-bonding geometries did not indicate hydrogen-bond strengthening under high pressure. Compared with Mg(OD)2, the doping of F suppressed the increase of the hydroxyl covalent bond length, the hydrogen-bond angle, and the cone angle, inhibiting pressure-induced hydrogen-bond strengthening. High-pressure Raman and IR absorption spectroscopic measurements on Mg(OD)2 and Mg(OD)1.79F0.21 up to 9.7 and 13.7 GPa confirmed that F substitution restrains pressure-induced hydroxyl elongation.

New insights of emerald geographic origin determination based on the infrared spectroscopy of D2O and HDO molecules

Emerald geographic origin determination in laboratories typically relies on the microscopic features of inclusions, ultraviolet through visible and near-infrared (UV-Vis-NIR) spectroscopy, and trace element chemistry measured by laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS). Infrared (IR) spectroscopy, a non-destructive technique, has played a minor role in this process. This work conducts a systematic examination of emerald samples from twelve origins, encompassing spectroscopic, and trace element analyses. For the first time, IR absorptions related to D2O and HDO molecules within the 2600–2850 cm–1 range from multiple origins (333 emerald samples) were recorded, assigned, and classified. These IR absorptions, controlled by the concentrations of deuterium (D) and alkali metals (primarily sodium) within channels, reveal three distinct patterns and derived four groups that serve as strong evidence for origin determination. Emeralds from Zambia group display the most prevalent HDO-dominant IR-pattern I characterized by the pronounced absorption peak of Type II HDO at 2672 cm–1; Panjshir (Afghanistan) and Swat (Pakistan) emeralds exhibit the transitional type IR-Pattern II with overall five peaks and obvious 2808 cm–1 peak; D2O-dominant IR-Pattern III is featured by marked absorption band at 2740 cm–1, and can be further subdivided into two subtypes (IIIa and IIIb). IR-Pattern IIIb is currently only found in Nigerian emeralds, characterized by strong broad band of Type I D2O due to enriched deuterium and obvious absorption of Type I HDO at 2685 cm–1 due to depleted sodium. Furthermore, this research updates the classification of UV-Vis-NIR spectra, unveils the trace element features, and presents effective compositional diagrams. This contribution enriches and expands existing techniques and provides new insights for emerald origin determination.

Study on the optical properties of Sm3+ doped bismuth silicate crystals based on first principles

Abstract This study systematically investigated the effect of Sm3+ doping on the optical properties of bismuth silicate (Bi4Si3O12, abbreviated as BSO) crystals using first principles calculations based on density functional theory (DFT). By calculating the dielectric function, reflectivity, absorption coefficient, refractive index, conductivity, and energy loss function of BSO crystals under different Sm3+ doping ratios, we found that moderate Sm3+ doping can increase the dielectric function of BSO crystals, and the real part of the dielectric function represents the material’s ability to respond to the electric field, that is, the macroscopic polarization degree. Therefore, moderate Sm3+ doping enhances the polarization ability of BSO crystals. Simultaneously doping an appropriate amount can effectively enhance the conductivity and light (visible and infrared) absorption ability of BSO crystals, and reduce the energy loss between electrons in BSO crystals, thereby improving their luminescence performance. Specifically, when the Sm3+ doping ratio is 1/6, the optical properties of BSO crystals are significantly improved. These findings not only enhance the understanding of the mechanism of optical performance changes in rare earth ion doped BSO crystals, but also provide a theoretical basis for the development of new rare earth doped optical materials.

Hydrogen Spillover-Bridged Interfacial Water Activation of WCx and Hydrogen Recombination of Ru as Dual Active Sites for Accelerating Electrocatalytic Hydrogen Evolution.

Tungsten carbide (WCx) is a promising alternative to platinum catalysts for hydrogen evolution reaction (HER). However, strong tungsten-hydrogen bond hinders hydrogen desorption while favoring H+ reduction, thus limiting HER kinetics. Inspired by the phenomenon of hydrogen spillover in heterogeneous catalysis, a ruthenium (Ru) doped-driven activated hydrogen migration from WCx surface to Ru is reported. This approach achieved high activity with an ultralow overpotential of 9.0mV at 10 mA·cm-2 and superior stability at an industrial-grade current density of 1.0 A·cm-2 @ 1.65V. In situ attenuated total reflectance surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS)and operando electrochemical impedance spectra revealed that this exceptional hydrogen production-which surpasses that of previously reported Pt/C catalysts-is attributable to the outstanding ability of WCx to induce water dissociation and hydrogen spillover from WCx to Ru surface. During the HER process, the rigid interfacial water network negatively affected the HER efficiency under alkaline conditions. The WCx sites disrupted this rigid structure, facilitating the contact between activated hydrogen (H*) and WCx sites. Subsequently, H* migrates to Ru surface, where hydrogen recombination occurs to produce H2. This work paves a new avenue for the construction of coupled catalysts at the atomic scale to facilitate HER electrocatalysis.

Covalent Organic Framework Stabilized Single CoN4Cl2 Site Boosts Photocatalytic CO2 Reduction into Tunable Syngas.

Solar carbon dioxide (CO2) reduction provides an attractive alternative to producing sustainable chemicals and fuel. However, the construction of a highly active photocatalyst was challenging because of the rapid charge recombination and sluggish surface CO2 reduction. Herein, a unique Co-N4Cl2 single site was fabricated by loading Co species into the 2,2'-bipyridine and triazine-containing covalent organic framework (COF) for CO2 conversion into syngas under visible light irradiation. The resulting champion catalyst TPy-COF-Co enabled a record-high CO production rate of 426 mmol g-1 h-1, associated with the unprecedented turnover number (TON) and turnover frequency (TOF) of 2095 and 1607 h-1, respectively. The catalyst also exhibited favorable recycling performance and widely adjustable syngas production (CO/H2 ratio: 1.8 : 1-1 : 16). A systematical investigation including operando synchrotron X-ray absorption fine structure (XAFS) spectroscopy, in situ attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS), and theoretical calculation indicated that the triazine-based COF framework promoted the charge transfer towards the single Co-N4Cl2 sites that greatly promoted the CO2 activation by lowering the energy barrier of *COOH generation, facilitating the CO2 transformation. This work highlights the great potential of the molecular regulation of COF-derived single-atom catalysts to boost CO2 photoreduction efficiency.

Evidence for Distinct Active Sites on Oxide-Derived Cu for Electrochemical Nitrate Reduction.

Cu is a promising catalyst for electrochemical nitrate (NO3-) reduction. However, desorption of the nitrite (NO2-) intermediate can occur, leading to lowered ammonia productivity and Faradaic efficiency. Here, we discovered that this does not occur with oxide-derived Cu due to the presence of at least two distinct types of cooperative active sites: one for NO3- → NO2- and another for NO2- → NH3. As a result, oxide-derived Cu exhibits enhanced ammonia productivity with a mixed NO3-/NO2- feed relative to pure NO3- or NO2-. In contrast, this was not observed with a standard Cu sample, implying the presence of only a single type of active site. Our dual-site hypothesis was supported by attenuated total reflection surface enhanced infrared absorption spectroscopy and isotopic labeling experiments involving co-reduction of 15NO3-/14NO2-. We also successfully simulated our experimental results using a mathematical model involving two different adsorption sites. These findings motivate the need for further study and rational design of such active sites.

The first satellite measurements of HFC-125 by the ACE-FTS: Long-term trends and distribution in the Earth’s upper troposphere and lower stratosphere

HFC-125 (CF3CHF2, pentafluoroethane) volume mixing ratios (VMRs) have been determined for the first time using infrared absorption spectra from the Atmospheric Chemistry Experiment Fourier transform spectrometer (ACE-FTS) from 2004 to 2024. These VMRs provide global altitude-latitude VMR distributions. A VMR time series for HFC-125 has also been calculated and compared to values from in situ discrete flask measurements conducted by the National Oceanic and Atmospheric Administration Earth System Research Laboratory. The abundance of HFC-125 is currently experiencing exponential growth. ACE data shows a growth rate of 3.47 ± 0.05 ppt/year in the past six years.

Solution-Crystalized AgBiS2 Films for Solar Cells Generating a Photo-Current Density Over 31mA cm-2.

In response to the toxic heavy metal absorbers in perovskite solar cells (PSCs), this work focuses on the development of an environmentally friendly simple solution-processed infrared (IR) absorber. In this work, a simple solution-crystallized IR-absorbing AgBiS2 film is reported by spin-coating silver, bismuth nitrates, and thiourea dissolved in dimethylformamide (DMF) to produce thick AgBiS2 film. Extensive optimization of the precursor concentrations thicknesses and conductive substrates used allow for obtaining 250nm AgBiS2 film with different crystal sizes. When applied as an absorber in solar cells, solution-crystalized AgBiS2 thick film delivers an extraordinarily high current density of over 31mA cm-2. The devices show high stability under continuous 100mW cm-2 illumination and when stored in the dark for more than six months. When the AgBiS2 layer is fabricated in a gradient fashion combining one layer of 0.25m and three layers of 0.5m precursor concentrations, the efficiency of 5.15% is registered which is the highest reported for the simple solution-crystallized AgBiS2 films.

Unveiling the Structure and Dissociation of Interfacial Water on RuO2 for Efficient Acidic Oxygen Evolution Reaction.

Understanding the structure and dynamic process of interfacial water molecules at the catalyst-electrolyte interface on acidic oxygen evolution reaction (OER) kinetics is highly desirable for the development of proton exchange membrane water electrolyzers. Herein, we construct a series of p-block metal elements (Ga, In, Sn) doped RuO2 catalysts with manipulated electronic structure and Ru-O covalency to investigate the effect of electrochemical interfacial engineering on the improvement of acidic OER activity. Associated with operando attenuated total reflectance surface-enhanced infrared absorption spectroscopy measurements and theoretical analysis, we uncover the free-H2O enriched local environment and dynamic evolution from 4-coordinated hydrogen-bonded water and 2-coordinated hydrogen-bonded water to free-H2O on the surface of Ga-RuO2, are responsible for the optimized connectivity of hydrogen bonding network in the electrical double layer by promoting solvent reorganization. In addition, the structurally ordered interfacial water molecules facilitate high-efficiency proton-coupled electron transfer across the interface, leading to reduced energy barrier of the follow-up dissociation process and enhanced acidic OER performance. This work highlights the key role of structure and dynamic process of interfacial water for acidic OER, and demonstrates the electrochemical interfacial engineering as an efficient strategy to design high-performance electrocatalysts.

Designing a one-dimensional photonic crystal sensor for dimethyl methylphosphonate detection leveraging a hydrogen-bonding-based acidic strategy

Chemical warfare agents (CWAs) are extremely toxic chemicals, necessitating rapid, easy-to-use, sensitive and selective sensors for detection. Dimethyl methylphosphonate (DMMP) serves as a simulant of nerve agents and is commonly used to evaluate the efficacy of sensors in detecting these hazardous compounds. In this context, this paper proposes a one-dimensional (1D) photonic crystal (PC) gas sensor functionalised with UIO-66-COOH, leveraging a hydrogen-bonding-based acidic strategy, for rapid and sensitive DMMP detection. To optimise DMMP uptake, the organic ligand, UIO-66, is functionalised by grafting additional carboxyl groups to facilitate hydrogen-bonding interactions with the PO groups of organophosphorus gases such as DMMP. Subsequently, attenuated total reflection surface-enhanced infrared absorption spectroscopy is performed to quantitatively monitor the impact of strong interactions between the PC bonds and PO bonds of DMMP and the adsorption sites of metal–organic frameworks (MOFs) during adsorption. The results reveal an increase in the number of hydrogen-bonding sites available for DMMP adsorption, thus promoting hydrogen-bonding interactions. Furthermore, density functional theory calculations are employed to analyse the presence and strength of hydrogen bonds between the MOFs and DMMP. The results reveal that the chemisorption energy of UIO-66-COOH exceeds those of its variants, corroborating the findings of sensing experiments. Overall, the developed 1D PC gas sensor comprising UIO-66-COOH/TiO2 demonstrates excellent stability and reproducibility, with a limit of detection of 0.3 ppm. This sensor also demonstrates enhanced selectivity towards organophosphorus gases compared to volatile organic compounds.

Enhanced CO2 Electroreduction to ethylene on Cu nanocube coated with nitrogen-doped carbon shell in-situ electro-derived from metal-organic framework

Electrochemical CO2 reduction reaction (CO2RR) to ethylene is one of the most promising technologies to achieve efficient use of carbon resources and sustainable development, in which the development of an efficient and stable electrocatalyst is particularly important. In this work, we develop a catalyst in situ electro-derived from Cu-based MOF for CO2RR to ethylene. We prepared nano Cu-MOF by microwave synthesis and supported it on a Cu foil substrate as a working electrode (denoted as MOF/Cu foil). During in situ electrolysis, Cu-MOF was converted into a highly dispersed nitrogen-doped carbon-coated Cu nanocube (denoted as Cu-cube/CN), which inhibited particle agglomeration and enhanced active site exposure. At a potential of −1.15 V vs. RHE, the Faradaic efficiency (FE) of the Cu-cube/CN catalyst for ethylene is 49.6 %, significantly higher than that of the original Cu foil electrode and Cu-MOF supported on the gas diffusion layer (GDL) prepared working electrode (denoted as MOF/GDL). In situ attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) and density functional theory (DFT) calculations studies indicate that due to the electron-donating ability of the CN coating, the adsorption of *CO is enhanced, increasing the *CO coverage, lowering the reaction free energy of *CO dimerization, promoting C-C coupling and ethylene generation. This work provides new insights for the development of efficient and stable electrocatalysts for CO2RR-to-ethylene production.

Operando Spectroscopic Investigation of the Re2O7.2H2O Adduct obtained by Controlled Hydration of Re2O7.

We provide here a comprehensive investigation spectroscopic of the controlled hydration of Re2O7 using Raman, Fourier-Transform Infrared (FTIR) and X-Rays Absorption (XAS) techniques in complement with ab initio modelling for confirming the spectral assignments. Hence, the Raman signature of Re2O7.2H2O was obtained, and the evolution kinetics was investigated to provide a detailed description of the hydration process.

Bandgap Engineering via Doping Strategies for Narrowing the Bandgap below 1.2 eV in Sn/Pb Binary Perovskites: Unveiling the Role of Bi3+ Incorporation on Different A-Site Compositions.

The integration of perovskite materials in solar cells has garnered significant attention due to their exceptional photovoltaic properties. However, achieving a bandgap energy below 1.2 eV remains challenging, particularly for applications requiring infrared absorption, such as sub-cells in tandem solar cells and single-junction perovskite solar cells. In this study, we employed a doping strategy to engineer the bandgap and observed that the doping effects varied depending on the A-site cation. Specifically, we investigated the impact of bismuth (Bi3+) incorporation into perovskites with different A-site cations, such as cesium (Cs) and methylammonium (MA). Remarkably, Bi3+ doping in MA-based tin-lead perovskites enabled the fabrication of ultra-narrow bandgap films (~1 eV). Comprehensive characterization, including structural, optical, and electronic analyses, was conducted to elucidate the effects of Bi doping. Notably, 8% Bi-doped Sn-Pb perovskites demonstrated infrared absorption extending up to 1360 nm, an unprecedented range for ABX3-type single halide perovskites. This work provides valuable insights into further narrowing the bandgap of halide perovskite materials, which is essential for their effective use in multi-junction tandem solar cell architectures.

Alkaline-Metal Cations Affect Pt Deactivation for the Electrooxidation of Small Organic Molecules by Affecting the Formation of Inactive Pt Oxide.

The activity of Pt for the electro-oxidation of several organic molecules changes with the cation of the electrolyte. It has been proposed that the underlying reason behind that effect is the so-called noncovalent interactions between the hydrated cations and adsorbed OH (OHad). However, there is a lack of spectroscopic evidence for this phenomenon, resulting in an incomplete understanding at the microscopic level of these electrochemical processes. Herein, we explore the electro-oxidation of glycerol (EOG) on platinum (Pt) in LiOH, NaOH and KOH using in situ surface-enhanced infrared absorption spectroscopy in the attenuated total reflectance mode (ATR-SEIRAS) and in situ X-ray absorption spectroscopy (XAS). Our results show that the electrolyte cation influences the rate and potential at which adsorbed CO (COad), a catalytic poison, is formed and oxidized. We attribute this to the cation-dependent stability of oxygenated species on the metallic Pt surface and the different intensities of the electric field at the electrode/electrolyte interface. We also demonstrate that the formation of an inactive Pt oxide layer is indirectly also cation-dependent: the formation of this layer is triggered by the cation-dependent oxidative removal of reaction intermediates (for instance, CO). This phenomenon explains the well-known cation-induced differences in the voltammetric profiles, of not just glycerol, but generally of alcohols and polyols.