Infrared Absorption Spectroscopy Research Articles

(Energy Technology Division Graduate Student Award sponsored by BioLogic) Probing and Engineering Electrode-Electrolyte Interfaces in Electrochemical Energy Storage and Conversion

Climate change demands the development of clean energy technologies, where rechargeable batteries and fuel cells promise a bright future by integrating with solar or wind energy. Li-ion batteries and fuel cells also play essential roles in electrifying transportation in replacement of internal combustion engines. Central to these electrochemical systems is the electrode-electrolyte interface, where (electro)chemical surface reactions or intercalation reactions occur, and its thermodynamic and kinetic properties determine the energy density, power density, and lifetime of the electrochemical devices. However, the molecular structures at the interface and how they promote or suppress the desired reactions remain unclear, hindering the rational design of electrode-electrolyte interfaces to improve the performance of electrochemical devices.This talk focuses on the fundamental understanding of the interfacial (electro)chemical reaction mechanisms at the molecular level and charges transfer kinetics at the electrified interfaces. First, an in situ Fourier-transform infrared spectroscopy (FTIR) method was developed to examine the parasitic reactions between carbonate electrolytes and lithium nickel, manganese and cobalt oxides (NMC) in Li-ion batteries, and unique evidence for dehydrogenation reactions on Ni-rich NMC was revealed, which accounted for interface impedance build-up and battery capacity fading. Based on the proposed mechanism, strategies based on electrolyte non-covalent interactions were demonstrated to improve battery lifetime. In the second part of the talk, the research extended in situ FTIR characterization and electrolyte engineering to electrocatalytic reactions central to fuel cell technologies. An interfacial layer of protic ionic liquids with different acid dissociation constants were found to enhance the oxygen-reduction reaction (ORR), attributed to strengthened hydrogen bonding between ORR products and ionic liquids, revealed by in situ surface-enhanced infrared absorption spectroscopy and density functional theory (DFT) calculations. For the hydrogen evolution reaction (HER), similarly, promoting hydrogen bonding between interfacial water molecules also facilitated proton-coupled electron transfer kinetics, resulting in favorable HER in controllable organic confinements. Finally, this talk will introduce fundamental, theoretical aspects of charge transfer processes at the electrode-electrolyte interface - the kinetic mechanism for ion intercalation. Experimental evidence from a charge-adjusted electrochemical method showed that Li-ion intercalation occurs by coupled ion-electron transfer (CIET), which governs the current-dependent maximum capacity and power density of intercalation batteries. these research efforts have laid a solid foundation for the rational design of electrochemical interfaces employing the physical chemistry of electrodes and electrolytes, for next-generation electrochemical storage devices with improved energy and power density and cycle life.

Research opportunities of surface enhanced infrared absorption spectroscopy on adsorption behavior of additives for electroplating

Research opportunities of surface enhanced infrared absorption spectroscopy on adsorption behavior of additives for electroplating

Research Progress in Surface-Enhanced Infrared Absorption Spectroscopy: From Performance Optimization, Sensing Applications, to System Integration.

Infrared absorption spectroscopy is an effective tool for the detection and identification of molecules. However, its application is limited by the low infrared absorption cross-section of the molecule, resulting in low sensitivity and a poor signal-to-noise ratio. Surface-Enhanced Infrared Absorption (SEIRA) spectroscopy is a breakthrough technique that exploits the field-enhancing properties of periodic nanostructures to amplify the vibrational signals of trace molecules. The fascinating properties of SEIRA technology have aroused great interest, driving diverse sensing applications. In this review, we first discuss three ways for SEIRA performance optimization, including material selection, sensitivity enhancement, and bandwidth improvement. Subsequently, we discuss the potential applications of SEIRA technology in fields such as biomedicine and environmental monitoring. In recent years, we have ushered in a new era characterized by the Internet of Things, sensor networks, and wearable devices. These new demands spurred the pursuit of miniaturized and consolidated infrared spectroscopy systems and chips. In addition, the rise of machine learning has injected new vitality into SEIRA, bringing smart device design and data analysis to the foreground. The final section of this review explores the anticipated trajectory that SEIRA technology might take, highlighting future trends and possibilities.

Highly selective NH3 synthesis from N2 on electron-rich Bi0 in a pressurized electrolyzer

Electrochemical conversion of N2 into ammonia presents a sustainable pathway to produce hydrogen storage carrier but yet requires further advancement in electrocatalyst design and electrolyzer integration. This technology suffers from low selectivity and yield owing to the extremely strong N≡N bond and the exceptionally low solubility of N2 in aqueous systems. A high NH3 synthesis performance is restricted by the high activation energy of N≡N bond and the supply insufficiency of N2 to active sites. This paper describes the introduction of electron-rich Bi0 sites into Ag catalysts with a high-pressure electrolyzer that enables a dramatically enhanced Faradaic efficiency of 44.0% and yield of 28.43 μg cm-2 h-1 at 4.0 MPa. Combined with density functional theory results, in situ attenuated total reflectance surface-enhanced infrared absorption spectroscopy demonstrates that N2 reduction reaction follows an associative mechanism, in which a high coverage of N-N bond and -NH2 intermediates suggest electron-rich Bi0 boosts sound activation of N2 molecules and low hydrogenation barrier. The proposed strategy of engineering electrochemical catalysts and devices provides powerful guidelines for achieving industrial-level green ammonia production.

Effect of pH on Electrochemical Impedance Response of Tethered Bilayer Lipid Membranes: Implications for Quantitative Biosensing

Tethered bilayer lipid membranes (tBLMs) are increasingly used in biosensor applications where electrochemical impedance spectroscopy (EIS) is the method of choice for amplifying and recording the activity of membrane-damaging agents such as pore-forming toxins or disrupting peptides. While the activity of these biological agents may depend on the pH of the analytes, there is increasing evidence that the sensitivity of tethered bilayer sensors depends on the pH of the solutions. In our study, we addressed the question of what are the fundamental reasons for the variability of the EIS signal of the tBLMs with pH. We designed an experiment to compare the EIS response of tBLMs with natural membrane defects and two different membrane disruptors: vaginolysin and melittin. Our experimental design ensured that the same amount of protein and peptide was present in the tBLMs, while the pH was varied by replacing the buffers with different pH values. Using a recently developed EIS data analysis algorithm from our research group, we were able to demonstrate that, in contrast to previous literature which relates the variability of tBLM, EIS response to the variation in defect density, the main reason for the observed variability in EIS response is the change in the sub-membrane properties of tBLMs with pH. Using surface-enhanced infrared absorption spectroscopy (SEIRAS), we have shown that pH changes from neutral to slightly acidic leads to an expulsion of water, presumably bound to ions, from the sub-membrane reservoir, resulting in a marked decrease in the carrier concentration and specific conductance of the sub-membrane reservoir. Such a decrease is recorded by the EIS as a decrease in the conductance of the tBLM complex and affects the sensitivity of a biosensor. Our data provide important evidence of pH-sensitive effects that should be considered in both the development and operation of biosensors.

Identifying Adsorbed OH Species on Pt and Ru Electrodes with Surface-Enhanced Infrared Absorption Spectroscopy through CO Displacement.

OH adspecies are involved in numerous electrocatalytic reactions, such as CO, H2, methanol, and ethanol oxidation and oxygen reduction reactions, as a reaction intermediate and/or reactant. In this work, we have, for the first time, identified the OH stretching band of OH adspecies on Pt, Ru, and Pt/Ru electrodes with surface-enhanced infrared absorption spectroscopy (SEIRAS) in a flow cell through potential modulation and CO displacement. We found that while Ru had a relatively constant OH coverage at potentials between 0.1 and 0.8 V, Pt had a maximum OH coverage at 0.6 V in 0.1 M HClO4 and 0.7 V in 0.1 M KOH. CO oxidation kinetics on Ru were sluggish, although adsorbed OH appeared on Ru at very low potentials. Binary Pt/Ru electrodes promote CO oxidation through a synergistic effect in which Ru promotes OH adsorption and Pt catalyzes the reaction between the CO and OH adspecies. In addition, water coadsorbed with CO at Ru sites of Pt/Ru also plays an important role. These new spectroscopic results about OH adspecies could advance the understanding of the mechanism of fuel cell related electrocatalysis.

Effect of Coconut Fiber Biochar and Its Nitrate Modification on Pb Passivation in Paddy Soils

The effects of coconut fiber biochar (CFB) and nitrate-modified coconut fiber biochar (NCFB) on the passivation of exogenous lead (Pb) in paddy soils and their underlying mechanisms were investigated using soil incubation experiments combined with spectroscopic techniques such as scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), synchrotron radiation X-ray fluorescence (SRXRF), and Fourier transform infrared absorption spectroscopy (FTIR). The effects of NCFB and CFB on the passivation of exogenous lead (Pb) in paddy soils and its underlying mechanisms were investigated. Compared with that of CFB, the inner wall of NCFB honeycomb pores was rougher, and the amount of alcohol-phenol-ether functional groups containing the C-O structure and the amount of carboxyl groups containing the C[FY=,1]O/O[FY=,1]C-O structure on the surface of CFB was significantly decreased after nitric acid modification. Compared with that in the control (without biochar) paddy soil after 150 d of incubation, the EDTA-extracted Pb content in the paddy soil with CFB and NCFB was reduced by 39.7% and 105.4%, respectively. The carbonate-bound and Fe-Mn oxide-bound Pb contents were significantly lower, and the organic-bound and residue Pb contents were significantly higher in the NCFB-added soil. The SRXRF scans showed that the exogenous Pb was enriched in the microregions of CFB particles rich in Ca and Cu elements and relatively less so in the microregions of soil aggregates rich in the Fe, Mn, and Ti elements. In addition, the characteristic peaks of carboxylates (1384 cm-1) in A-CFBPb and A-NCFBPb were significantly enhanced in the incubation experiment in the presence of exogenous Pb compared to A-CFB and A-NCFB in the absence of exogenous Pb. The addition of CFB or NCFB was more effective in passivating exogenous Pb in paddy soils and promoted the gradual transformation of Pb from unstable to more stable forms in paddy soils to achieve the effect of passivating Pb. The greater amount of carboxyl functional groups in NCFB participated in the passivation of exogenous Pb, which made NCFB more effective than CFB in passivating Pb. NCFB was more effective than CFB in passivating exogenous Pb in paddy soils due to its rougher inner walls of honeycomb pores and abundant carboxyl functional groups. In tropical areas such as Hainan, coconut fiber biochar and its modification can be considered as an environmentally friendly candidate method for the remediation of soil Pb contamination.

The electrocatalytic activity and selectivity of ethylene glycol oxidation into value-added chemicals at iron-group electrodes in alkaline media

Selective electrocatalytic conversion via ethylene glycol oxidation reaction (EGOR) at abundant Iron-group catalysts could be a promising and sustainable approach to produce value-added C1 and C2 chemicals. However, the corresponding intrinsic electrocatalytic activity and selectivity of EGOR on Iron-group electrodes are still ambiguous, which is urgent to be revealed. The linear scanning voltammetry (LSV) results show that Co and Ni rather than Fe exhibit considerably high activity, and the CoIV and NiIII sites formed at high potential might be crucial for the fast EGOR revealed by LSV and operando electrochemical impedance spectroscopy (EIS). Then, the in-situ electrochemical infrared absorption spectroscopy (IRAS) and high-performance liquid chromatography (HPLC) are used to obtain a general understanding of reaction pathways and product distributions in alkaline media. Specifically, a parallel C1 pathway (formate) without CO2 generation and C2 pathway (glycollate, oxalate) is confirmed on Co and Ni surfaces. The C1 pathway is dominated on the Ni surface with a ∼60% selectivity of formate, while the C2 pathway is favorable on the Co surface with a ∼43% selectivity of glycollate at 1.60 V vs. RHE. In addition, the Ni electrode showed a higher yield rate of carboxylate products. This work may offer theoretical guidance for the design of noble-metal-free electrocatalysts towards efficient selective electrooxidation of EG to value-added chemicals.

Stabilizing highly active atomically dispersed NiN4Cl sites by Cl‐doping for CO2 electroreduction

AbstractNickel‐nitrogen‐carbon single‐atom catalysts have attracted widespread interest for CO2 electroreduction but they suffer from poor stability. Herein, we report on the preparation of Cl‐ and N‐doped porous carbon nanosheets with atomically dispersed NiN4Cl active sites (NiN4Cl‐ClNC) through a molten‐salt‐assisted pyrolysis strategy. The optimized NiN4Cl‐ClNC catalyst delivers exceptional CO2 conversion activity with outstanding stability for over 220 h at −0.7 V versus RHE and a high CO Faradaic efficiency of 98.7% at a CO partial current density of 12.4 mA cm‒2. Moreover, NiN4Cl‐ClNC displays a remarkable CO partial current density of approximately 349.4 mA cm−2 in flow‐cell, meeting the requirements of industrial applications. Operando attenuated total reflectance surface‐enhanced infrared absorption spectroscopy and density functional theory calculations are used to understand the outstanding activity and stability. Results reveal that the introduced axial Ni‐Cl bond on the Ni center and Cl─C bond on the carbon support synergetically induce electronic delocalization, which not only stabilizes Ni against leaching but also facilitates the formation of the COOH* intermediate that is found to be the rate‐determining step.

Photochemistry sample sticks for inelastic neutron scattering.

Every material experiences atomic and molecular motions that are generally termed vibrations in gases and liquids or phonons in solid state materials. Optical spectroscopy techniques, such as Raman, infrared absorption spectroscopy, or inelastic neutron scattering (INS), can be used to measure the vibrational/phonon spectrum of ground state materials properties. A variety of optical pump probe spectroscopies enable the measurement of excited states or elucidate photochemical reaction pathways and kinetics. So far, it has not been possible to study photoactive materials or processes in situ using INS due to the mismatch between neutron and photon penetration depths, differences between the flux density of photons and neutrons, cryogenic temperatures for INS measurements, vacuum conditions, and a lack of optical access to the sample space. These experimental hurdles have resulted in very limited photochemistry studies using INS. Here we report on the design of two different photochemistry sample sticks that overcome these experimental hurdles to enable in situ photochemical studies using INS, specifically at the VISION instrument at Oak Ridge National Laboratory. We demonstrate the use of these new measurement capabilities through (1) the in situ photodimerization of anthracene and (2) the in situ photopolymerization of a 405nm photoresin using 405nm excitation as simple test cases. These new measurement apparatus broaden the science enabled by INS to include photoactive materials, optically excited states, and photoinitiated reactions.

In Situ Topochemical Transformation of ZnIn2S4 for Efficient Photocatalytic Oxidation of 5‐Hydroxymethylfurfural to 2,5‐Diformylfuran

AbstractPhotocatalytic selective oxidation of 5‐hydroxymethylfurfural (HMF) coupled H2 production offers a promising approach to producing valuable chemicals. Herein, an efficient in situ topological transformation tactic is developed for producing porous O‐doped ZnIn2S4 nanosheets for HMF oxidation cooperative with H2 evolution. Aberration‐corrected high‐angle annular dark‐field scanning TEM images show that the hierarchical porous O‐ZIS‐120 possesses abundant atomic scale edge steps and lattice defects, which is beneficial for electron accumulation and molecule adsorption. The optimal catalyst (O‐ZIS‐120) exhibits remarkable performance with 2,5‐diformylfuran (DFF) yields of 1624 µmol h−1 g−1 and the selectivity of >97%, simultaneously with the H2 evolution rate of 1522 µmol h−1 g−1. Mechanistic investigations through theoretical calculations show that O in the O‐ZIS‐120 lattice can reduce the oxidation energy barrier of hydroxyl groups of HMF. In situ attenuated total reflection surface‐enhanced infrared absorption spectroscopy (ATR‐SEIRAS) results reveal that DFF* (C4H2(CHO)2O*) intermediate has a weak interaction with O‐ZIS‐120 and desorb as the final product. This study elucidates the topotactic structural transitions of 2D materials simultaneously with electronic structure modulation for efficient photocatalytic DFF production.

In situ infrared absorption spectroscopy of cryogenic-specific reddish coloration produced by cryoplasma irradiation on an ice surface

Recently, cryoplasma has been demonstrated to form reddish coloration on methanol- and water-containing ice surfaces below 150 K. This cryogenic-temperature-only reddish coloration could provide a clue for understanding the composition of the red organic materials observed in the outer solar system. In this study, ice with reddish coloration was analyzed by IR absorption spectroscopy (2500–1700 cm−1) during cryoplasma irradiation at 85 K and subsequent increase of the temperature from 85 to 200 K without cryoplasma. The intensities of the IR peaks, differing from those of the raw materials, increased with the irradiation time during reddish coloration. When the reddish coloration disappeared at 120–150 K, the IR peak intensities at 2170 and 1790 cm−1 decreased. These peaks are thought to originate from C- and/or N-containing triple bonds or cumulative double bonds and carbonyl groups. Therefore, the reddish materials are considered to contain these functional groups.

Experimental Investigation on Electric and Dielectric Properties of Thallium Ions Doped Sodium Zinc Phosphate Glass

Sodium zinc phosphate glasses modified by Tl2O addition of composition Na2−xTlxZnP2O7 (x = 0, 0.005, 0.01, and 0.015) are synthesized following the melt quenching technique. The structure of the glass samples is analyzed by the Fourier transform infrared absorption spectroscopy. The results suggest that the phosphate network is polymerized by the addition of Tl+ ions. The electrical conductivity, electric modulus, and dielectric constant characteristics of the glasses are measured over a wide continuous frequency range of 10−2 Hz–1 MHz and in the temperature range 293–473 K by the impedance spectroscopic method. The ac conductivity data are analyzed following the power law exponent (S) and the proposed correlated barrier hopping mechanism (CBH) is the most suitable conduction mechanism in the studied compositions. The electrical modulus formalism is applied to analyze the electric data to study their dielectric relaxation. Non‐Debye type relaxation is obtained. From the obtained results, the present glass can be used as a high‐energy capacitor.

Rh-dispersed Cu nanowire catalyst for boosting electrocatalytic hydrogenation of 5-hydroxymethylfurfural

Electrocatalytic conversion of biomass-derived 5-hydroxymethylfurfural (HMF) to 2,5-bis(hydroxymethyl)furan (BHMF) presents a compelling strategy for the production of premium chemicals via the utilization of renewable energy sources. Exploring efficient catalytic systems to obtain highly selective BHMF has remained a giant challenge. A design strategy is proposed here to regulate active hydrogen (Hads) production in rhodium (Rh) nanoparticles grown on Cu nanowires (RhCu NWs) catalyst, which achieves a faradaic efficiency (FE) of 92.6% in the electrocatalytic reduction of HMF to BHMF at −20 mA cm−2 with no degradation in performance after 8 cycles. Kinetic investigations and electron spin resonance (ESR) spectroscopy reveal that the incorporation of Rh accelerates the water dissociation and facilitates the generation of Hads. In situ attenuated total reflection surface enhanced infrared absorption spectroscopy (ATR-SEIRAS) further demonstrates that the Rh component boosts the proportion of ordered weakly hydrogen-bonded water molecules on the catalyst surface, which is much easier to dissociate. The construction of an interfacial Hads-rich environment promotes the HMF intermediates binding with Hads to BMHF, thereby suppressing the formation of undesired dimers. This work demonstrates the promise of altering the interfacial water environment as a strategy to boost the electrosynthetic properties of biomass-derived products toward value-added outcomes.

Crystal facet effect of γ-Al2O3 on catalytic property of CuO/γ-Al2O3 for CO oxidation

CuO/γ-Al2O3 is an important model catalyst and has received research attentions for a long-time. In this work, a special catalyst of CuO/γ-Al2O3 prepared using γ-Al2O3 nanotubes mainly exposing {111} planes as support, synthesized by a special method, was employed for CO oxidation and the impact of Its exposed facets on the properties of CuO/γ-Al2O3 catalyst was elaborately investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), electron spin resonance (ESR), temperature programmed reduction (TPR), and in situ infrared absorption spectroscopy of CO experiments (CO-IR). The results showed that the CuO species supported on {111} facet-exposed γ-Al2O3 nanotube had better dispersity and stronger interaction as comparing to the {110} facet-exposed γ-Al2O3 nanosheet, which could be reduced to Cu+ at lower temperature of 150 °C and thus formed into adsorbed COCu+ which was the necessary prerequisite for CO oxidation, and the activity test validated the CO were totally oxidized over the CuO/γ-Al2O3 with {111} plane below 230 °C. The improved catalytic activity of CuO/γ-Al2O3 by manipulating the exposed facets of crystal carrier offers a deep insight into the catalytic mechanism of loaded CuO species and points out the direction for the design of other catalyst systems.

Metal-Organic Framework Derived Cu-Ag Interface for Selective Carbon Monoxide Electroreduction to Acetate.

Electrochemical carbon monoxide reduction reaction (CORR) is a potential way to obtain high-value multi-carbon (C2+ ) products. However, achieving high selectivity to acetate is still a challenge. Herein, we develop a two-dimensional Ag-modified Cu metal-organic framework (Ag0.10 @CuMOF-74) that demonstrates Faradaic efficiency (FE) for C2+ products up to 90.4 % at 200 mA cm-2 and an acetate FE of 61.1 % with a partial current density of 122.2 mA cm-2 . Detailed investigations show that the introduction of Ag on CuMOF-74 favors the generation of abundant Cu-Ag interface sites. In situ attenuated total reflection surface enhanced infrared absorption spectroscopy confirms that these Cu-Ag interface sites improve the coverage of *CO and *CHO and the coupling between each other and stabilize key intermediates *OCCHO and *OCCH2 , thus significantly promoting to the acetate selectivity on Ag0.10 @CuMOF-74. This work provides a high-efficiency pathway for CORR to C2+ products.

Achieving Efficient CO2 Electrolysis to CO by Local Coordination Manipulation of Nickel Single-Atom Catalysts.

Selective electroreduction of CO2 to C1 feed gas provides an attractive avenue to store intermittent renewable energy. However, most of the CO2-to-CO catalysts are designed from the perspective of structural reconstruction, and it is challenging to precisely design a meaningful confining microenvironment for active sites on the support. Herein, we report a local sulfur doping method to precisely tune the electronic structure of an isolated asymmetric nickel-nitrogen-sulfur motif (Ni1-NSC). Our Ni1-NSC catalyst presents >99% faradaic efficiency for CO2-to-CO under a high current density of -320 mA cm-2. In situ attenuated total reflection surface-enhanced infrared absorption spectroscopy and differential electrochemical mass spectrometry indicated that the asymmetric sites show a significantly weaker binding strength of *CO and a lower kinetic overpotential for CO2-to-CO. Further theoretical analysis revealed that the enhanced CO2 reduction reaction performance of Ni1-NSC was mainly due to the effectively decreased intermediate activation energy.

CO Oxidation Catalyzed by Au Dispersed on SBA-15 Modified with TiO2 Films Grown via Atomic Layer Deposition (ALD)

It has been established that gold, when in nanoparticle (NP) form and in contact with reducible oxides, can promote oxidation reactions under mild conditions. Here, we report results from our exploration of the catalytic oxidation of carbon monoxide using catalysts where Au NPs were combined with thin titanium oxide films deposited on SBA-15 using atomic layer deposition (ALD). Both orders of deposition, with TiO2 added either before or after Au dispersion, were tested for two titania film thicknesses amounting to about half and full TiO2 monolayers. The resulting catalysts were characterized using various techniques, mainly electron microscopy and N2 adsorption–desorption isotherms, and the kinetics of the oxidation of CO with O2 were followed using infrared absorption spectroscopy. A synergy between the Au and TiO2 phases as it relates to the bonding and conversion of CO was identified, the tuning of which could be controlled by varying the synthetic parameters. The ALD of TiO2 films proved to be an effective way to maximize the Au-TiO2 interface sites, and with that help with the activation of molecular oxygen.

Ni-CeO2 Heterostructure Promotes Hydrogen Evolution Reaction via Tuning of the O-H Bond Length of Adsorbed Water at the Electrolyte/Electrode Interface.

Understanding the properties and structure of reactant water molecules at the electrolyte solution/electrode interface is relevant to know the mechanisms of hydrogen evolution reaction (HER). However, this approach has rarely been implemented due to the elusive local microenvironment in the vicinity of the catalyst. Taking the Ni-CeO2 heterostructure immobilized onto carbon paper (Ni-CeO2 /CP) as a model, the dynamic behavior of adsorbed intermediates during the reaction was measured by in situ surface-enhanced infrared absorption spectroscopy with attenuated total reflection configuration (ATR-SEIRAS). Theoretical calculations are used in combination to comprehend the potential causes of increased HER activity. The results show that the O-H bond of adsorbed water at the electrolyte solution/electrode interface becomes longer for promoting the dissociation of water and accelerating the kinetically slow Volmer step. In addition, forming the Ni-CeO2 heterostructure interface optimizes the hydrogen adsorption Gibbs free energy, thus increasing HER activity. Therefore, the Ni-CeO2 /CP electrode exhibits remarkably low HER overpotentials of 37 and 119 mV at 10 and 100 mA cm-2 , which are close to commercial Pt/C (16 and 102.6 mV, respectively).

Electrochemical Flow Reactor Design Allows Tunable Mass Transport Conditions for Operando Surface Enhanced Infrared Absorption Spectroscopy

AbstractIn situ attenuated total reflection surface enhanced infrared absorption spectroscopy (ATR‐SEIRAS) is often used to investigate the near‐surface electrocatalytic reaction environment. However, there is a gap in directly correlating the near‐surface reaction environment with electrocatalytic reaction rates. To that end, we designed an electrochemical flow reactor for operando electrochemical ATR‐SEIRAS and demonstrate its capability with the CO2 reduction reaction (CO2RR). Roughened gold catalyst thin films are prepared on ATR silicon crystals as a model system to probe local species under CO2RR conditions in 0.1 M KHCO3. We measured changes in the interfacial CO2 concentration as a function of applied potential and electrolyte flow rate in operando, allowing us to correlate the changes in reaction rates with the observed CO2 concentration. Including the choice of the catalyst and electrolyte, coupling hydrodynamic control with ATR‐SEIRAS in this platform enables investigations of how the local microenvironment affects the activity and selectivity of electrochemical reactions.