Total Reflection Surface-enhanced Infrared Absorption Research Articles

Novel water/oxygen cycle reaction photo fuel cell for solar conversion and pollutant detection: Based on selective 2-electron collaborative catalysis process

New typed photovoltaic devices, represented by water/oxygen cycle based photo fuel cells (PFCs) as a promising strategy to resolve the fossil energy crisis, have attracted extensive attention for the ideal photo energy conversion and utilization efficiency, spontaneous operation, and miniaturized devices. However, they still have limitations such as low oxygen reduction efficiency and poor stability caused by the complex structure of the cathode. In this work, a synergetic and fast 2-electron water/oxygen cycle reaction based dual-photoelectrode fuel cell (DPFC) is constructed with molecularly imprinted (MI)-CdS/ZnO nanorods (NRs) as photoanode and p-type organic semiconductor polythiophene (pTTh) as photocathode for the first time. The larger self-bias and simple structure endow the device higher open circuit potential (EOCV = 1.07 ± 0.08 V) and ideal output power density (Pmax = 60.5 ± 2.1 μW·cm−2). Attributed to the synergistic reaction effects, the 2-electron water/oxygen cycle is realized by the photocathode-generated H2O2 to serve as shuttle molecule, with outstanding cyclic stability (96 %) in 64 h continuous irradiation. Moreover, a portable self-powered sensor for the typical environmental pollutant atrazine is successfully developed based on this DPFC. A very wide concentration range (0.002 to 50 nM) and a super low detection limit (0.19 pM) is achived via a digital multimeter without the assistance of any signal amplifier. The mechanism, pathway, and active site of the selective reduction process are studied by the attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS). This work has proposed a cheap and regulatable new way to convert and utilize solar energy and provided theoretical guidance for achieving economic power generation and the sensing strategy of self-powered sensors.

Nanostructured Black Silicon as a Stable and Surface-Sensitive Platform for Time-Resolved In Situ Electrochemical Infrared Absorption Spectroscopy.

Attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) is a powerful method for probing interfacial chemical processes. However, SEIRAS-active nanostructured metallic thin films for the in situ analysis of electrochemical phenomena are often unstable under biased aqueous conditions. In this work, we present a surface-enhancing structure based on etched black Si internal reflection elements with Au-coatings for in situ electrochemical ATR-SEIRAS. Using electrochemical potential-dependent adsorption and desorption of 4-methoxypyridine on Au, we demonstrate that black Si-based substrates offer advantages over commonly used structures, such as electroless-deposited Au on Si and electrodeposited Au on ITO-coated Si, due to the combination of high stability, sensitivity, and conductivity. These characteristics are especially valuable for time-resolved measurements where stable substrates are required over extended times. Furthermore, the low sheet resistance of Au layers on black Si reduces the RC time constant of the electrochemical cell, enabling a significantly higher time resolution compared to that of traditional substrates. Thus, we employ black Si-based substrates in conjunction with rapid- and step-scan Fourier transform infrared (FTIR) spectroscopy to investigate the adsorption and desorption kinetics of 4-methoxypyridine during in situ electrochemical potential steps. Adsorption is shown to be diffusion-limited, which allows for the determination of the mean molecular area in a fully established monolayer. Moreover, no significant changes in the peak ratios of vibrational modes with different orientations relative to the molecular axis are observed, suggesting a single adsorption mode and no alteration of the average molecular orientation during the adsorption process. Overall, this study highlights the enhanced performance of black Si-based substrates for both steady-state and time-resolved in situ electrochemical ATR-SEIRAS, providing a powerful platform for kinetic and mechanistic investigations of electrochemical interfaces.

Kinetics Conditioning of (Electro) Chemically Stable Zn Anode with pH Regulation Toward Long-Life Zn-Storage Devices.

The safety, low cost, and high power density of aqueous Zn-based devices (AZDs) appeal to large-scale energy storage. Yet, the presence of hydrogen evolution reaction (HER) and chemical corrosion in the AZDs leads to local OH- concentration increasement and the formation of Znx SOy (OH)z •nH2 O (ZHS) by-products at the Zn/electrolyte interface, causing instability and irreversibility of the Zn-anodes. Here, a strategy is proposed to regulate OH- by introducing a bio-sourced/renewable polypeptide (ɛ-PL) as a pH regulator in electrolyte. The consumption of OH- species is evaluated through in vitro titration and cell in vivo in situ attenuated total reflection surface-enhanced infrared absorption spectroscopy at a macroscopic and molecular level. The introduction of ɛ-PL is found to significantly suppress the formation of ZHS and associated side reactions, and reduce the local coordinated H2 O of the Zn2+ solvation shell, widening electrochemical stable window and suppressing OH- generation during HER. As a result, the inclusion of ɛ-PL improves the cycle time of Zn/Zn symmetrical cells from 15 to 225h and enhances the cycle time of aqueous Zn- I2 cells to 1650h compared to those with pristine electrolytes. This work highlights the potential of kinetical OH- regulation for by-product and dendrite-free AZDs.

Exploration of a novel electrochemical C[sbnd]N coupling process: Urea synthesis from direct air carbon capture with nitrate wastewater

Direct air capture (DAC) can be used to decrease the CO2 concentration in the atmosphere, but this requires substantial energy consumption. If residual waste carbon (in the form of bicarbonate solution) from DAC can be directly reused, it might present a novel method for overcoming the aforementioned challenges. Electrochemical CN coupling methods for synthesizing urea have garnered considerable attention for waste carbon utilization, but the carbon source is high-purity CO2. No research has been conducted regarding the application of bicarbonate solution as the carbon source. This study proposes a proof-of-concept electrochemical CN coupling process for synthesizing urea using bicarbonate solution from DAC as the carbon source and nitrate from wastewater as the nitrogen source. These results confirmed the feasibility of synthesizing urea using a three-electrode system employing TF and CuInS2/TF as the working electrodes via potentiostatic electrolysis. Under the optimal conditions (initial pH 5.0 and applied potential of −1.3 V vs. Ag/AgCl), the urea yield after 2 h of electrolysis reached 3017.2 μg h−1 mgcat.−1 and an average Faradaic efficiency of 19.6 %. The in-situ attenuated total reflection surface-enhanced infrared absorption spectroscopy indicated a gradual increase in the intensity of the -CONH bond signal on the surface of the CuInS2/TF electrode as the reaction progressed. This implied that this bond may be a key chemical group in this process. The density functional theory calculations demonstrated that *CONH was a pivotal intermediate during CN coupling, and a two-step CN coupling reaction path was proposed. *NH + *CO primarily transformed into *CONH, followed by the conversion reaction of *CONH + *NO to *NOCONH2. This study offers a groundbreaking approach for waste carbon utilization from DAC and holds the potential to furnish technical underpinnings for advancing electrochemical CN coupling methods.

Investigating the Electrochemical CO2 Reduction Mechanism on Oxide-Derived Copper Using in Situ FTIR Spectroscopy

Oxide-derived copper (OD-Cu) electrocatalysts have been extensively used for CO2 reduction reaction (CO2RR) applications in recent years due to their capability to selectively produce valuable C2 compounds. The mechanism of CO2 reduction on these surfaces, however, is still not clearly understood. Using in situ attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS), we show how the copper pre-oxidation process can significantly influence the adsorption of various CO2RR intermediates. Upon mildly anodizing a Cu thin film, we observed a redshift on the *CO2 – band, indicating that the initial CO2 adsorption and activation step is promoted on the oxide-derived surface. Additionally, we observed a faster growth of the *COatop band for the anodized copper film at low overpotentials, which demonstrates how a high *CO coverage can be achieved on OD-Cu. Finally, for the first time, we observed the simultaneous formation of two bands at 1327 cm–1 and 1425 cm–1 on the anodized Cu thin film. Using DFT calculations, we show that these bands match the theoretical vibrational frequencies of the *COCHO dimer, a key intermediate of the C2 pathway. Furthermore, our calculations show that the thermodynamics of *CO and *CHO coupling can be improved in the presence of the subsurface oxygen sites in OD-Cu. Our findings reveal the different aspects through which the CO2 reduction mechanism can be improved on OD-Cu electrocatalysts as compared to metallic copper.This work was financially supported by the Research Grants Council (16310419, 16309418, and 16304821) and the Innovation and Technology Commission (grant no. ITC-CNERC14EG03).

Electrocatalytic ethanol-to-CO2 selectivity on the Ir electrode: A quasi-quantitative electrochemical infrared absorption spectroscopic investigation

Ir has long been regarded as an alternative ethanol-to-CO2 electrocatalyst, but little is known about the ethanol oxidation reaction (EOR) mechanism on Ir, especially the C1 pathway selectivity. Thereby, in situ quasi-quantitative electrochemical infrared absorption spectroscopy (QEIAS), consisting of total-reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS), infrared absorption spectroscopy (IRAS), and transmission infrared absorption spectroscopy (TIAS) with a thin-layer flow cell, is established to probe it. Initially, the well-accepted EOR dual-pathway mechanism is confirmed via ATR-SEIRAS and IRAS. Ir-Had species (ca. 2040 cm−1), originating from the ethanol dissociation at low potentials, are observed for the first time to replenish the reaction process. Based on it, the apparent Faradaic efficiency of the C1 pathway (FEC1) is readily estimated to be as high as 76.4% (0.7 V) in acidic media. The quantitative analysis of reaction residual verifies these FEC1 results through high-performance liquid chromatography (HPLC), and a relative error of only 2–9% exists between the two methods. Thus, Ir might be more efficient for ethanol complete oxidation than other Pt-group metallic catalysts, especially in acidic media. This work could be necessary for the rational design of Ir-based EOR catalysts with high C1 pathway selectivity and low over-potential for direct ethanol fuel cells.

Selective CO2 -to-Syngas Conversion Enabled by Bimetallic Gold/Zinc Sites in Partially Reduced Gold/Zinc Oxide Arrays.

Electrocatalytic CO2 -to-syngas (gaseous mixture of CO and H2 ) is a promising way to curb excessive CO2 emission and the greenhouse gas effect. Herein, we present a bimetallic AuZn@ZnO (AuZn/ZnO) catalyst with high efficiency and durability for the electrocatalytic reduction of CO2 and H2 O, which enables a high Faradaic efficiency of 66.4 % for CO and 26.5 % for H2 and 3 h stability of CO2 -to-syngas at -0.9 V vs. the reversible hydrogen electrode (RHE). The CO/H2 ratios show a wide range from 0.25 to 2.50 over a narrow potential window (-0.7 V to -1.1 V vs. RHE). In situ attenuated total reflection surface-enhanced infrared absorption spectroscopy combined with density functional theory calculations reveals that the bimetallic synergistic effect between Au and Zn sites lowers the activation energy barrier of CO2 molecules and facilitates electronic transfer, further highlighting the potential to control CO/H2 ratios for efficient syngas production using the coexisting Au sites and Zn sites.

Grain boundary-abundant copper nanoribbons on balanced gas-liquid diffusion electrodes for efficient CO2 electroreduction to C2H4

The electrocatalytic CO2 reduction reaction (CO2RR) is a promising technology to produce value-added hydrocarbon chemicals, however, achieving a high selectivity to C2+ products at the industrial current density remains a great challenge. Herein, we demonstrate grain boundary-abundant copper (Cu) nanoribbons on balanced gas-liquid diffusion electrodes for efficient CO2RR to ethylene (C2H4). The Cu(II) carbonate basic (Cu2CO3(OH)2) nanoribbon is used as a precursor to convert into metal Cu under in situ electrochemical reduction. Unexpectedly, the generated Cu nanoribbon is formed by stacking tiny nanoparticles with exposure of Cu(111), Cu(200) and Cu(220) facets, which creates abundant grain boundaries (GBs). During CO2RR test, the thickness of the catalyst layer is identified as a crucial factor for the mass transfer of CO2 and electrolyte. By tailoring the thickness of catalytic layer, CO2 and electrolyte can simultaneously reach the surface of catalyst and participate in CO2RR. Under the synergetic effects of GBs and balanced gas-liquid diffusion, the optimized electrode delivers the Faradaic efficiencies toward C2H4 and C2+ products as high as 67.2% and 82.1% at the current density of 700 mA cm−2, respectively. Moreover, the partial current density of C2H4 can reach up to 505 mA cm−2, which is significantly higher than most reported results. The in situ Raman and attenuated total reflection surface-enhanced infrared absorption spectra show that abundant GBs enhance the activation of CO2 and significantly promote the formation and adsorption of *CO intermediates, which accelerate C-C coupling to form *OCCO and *OCCOH intermediates and improve the production of C2H4 and other C2+ products.

Pb-Modified Ultrathin RuCu Nanoflowers for Active, Stable, and CO-resistant Alkaline Electrocatalytic Hydrogen Oxidation.

blem for hydrogen oxidation reaction (HOR), the anodic reaction of hydroxide exchange membrane fuel cell (HEMFC) for converting H2 to electric energy in sustainable manner. We demonstrate here an ultrathin Ru-based nanoflower modified with Pb (PbRuCu NF) as an active, stable, and CO-resistant catalyst for alkaline HOR. Mechanism studies show that the presence of Pb can weaken the adsorption of *H, strengthen *OH adsorption to facilitate CO oxidation, as a result of significantly enhanced HOR activity and improved CO tolerance. Furthermore, in-situ electrochemical attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) suggest that Pb acted as oxygen-rich site to regulate the behavior of the linear CO adsorption. The optimized Pb1.04-Ru92Cu8/C displays a mass activity and specific activity of 1.10 A mgRu-1 and 5.55 mA cm-2, which are ~10 and ~31 times higher than those of commercial Pt/C. This work provides a facile strategy for the design of Ru-based catalyst with high activity and strong CO-resistance for alkaline HOR, which may promote the fundamental researches on the rational design of functional catalysts.

In situ surface-enhanced infrared absorption analysis of the excited carrier transfer from n-type Si photoelectrode to Pt oxygen evolution cocatalyst by probing adsorbed CO molecules

BackgroundThe development of efficient photoelectrode material for water-splitting reactions has received considerable attention as it produces hydrogen gas from water using solar energy. Photoexcited holes migrate to the surface of an n-type photoelectrode oxidizing water to oxygen, and excited electrons migrate to the counter electrode reducing protons to hydrogen. However, there is limited knowledge of excited carrier transfer. MethodsTherefore, in situ attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) has been used to investigate the excited hole migration from n-type Si photoelectrode to Pt oxygen evolution cocatalysts by monitoring the frequency of CO adsorbed on the Pt cocatalysts. Significant findingsAt the positive potential of Si photoelectrode under UV irradiation, the SEIRA spectrum of the CO adsorbed on the Pt cocatalyst shifted to higher wavenumbers owing to the excited hole transfer from n-type Si photoelectrode to the Pt cocatalyst attributed to band bending at the interface between the Si photoelectrode and Pt cocatalysts. It was successfully demonstrated that the regulation of photoexcited carriers was crucial for enhancing the photoelectrochemical activity of water splitting.

Role of Electrolyte-Adsorbates Interaction in Determining CO2 Reduction Reaction Pathways

Electrochemical CO2 reduction reaction (CO2RR) is a promising strategy to convert atmospheric CO2 into valuable fuels and chemicals. Although the optimization of the catalyst-adsorbates interaction via tuning the binding energies of electrocatalysts has been extensively studied, activity and product selectivity remain a challenge. Recently, there has been a growing recognition that cations in electrolytes influence the activity of surface electrocatalytic reactions.1 A recent density functional theory study suggested that partially desolvated metal cations stabilize CO2RR intermediates via electrostatic interactions.2 Therefore, an experimental understanding of how the cations (and surrounding water molecules) control the intermediates present on the surface and govern the reaction pathway is critical to establish further insights into the design of electrolytes for CO2RR.In this talk, the role of alkali metal cations and water molecules on the CO2RR is revealed by tracking the surface-bound intermediates using operando attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS). We will also integrate the operando surface analysis with final product selectivity, further strengthening the understanding of the reaction mechanism. It will also be demonstrated that the holistic information about the electrolyte-adsorbates interaction can provide additional knobs to tune the energetics of key reaction intermediates, leading to further improvements in electrocatalytic activity for the CO2RR.[Reference]1 Ringe, S. et al., Energy Environ. Sci. 2019, 12, 3001–3014.2 Monteiro, MCO. et al., Nat. Catal. 2021, 4, 654–662.

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.

Reaction-induced iodine adsorption on Cu surfaces facilitates electrocatalytic CO2 reduction.

The electrolyte effect has been key to the electrochemical CO2 reduction reaction (CO2RR) and has received extensive attention in recent years. Here we combined atomic force microscopy, quasi-in situ X-ray photoelectron spectroscopy, and in situ attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) to study the effect of iodine anions on Cu-catalyzed CO2RR in the absence or presence of KI in the KHCO3 solution. Our results suggested that iodine adsorption caused coarsening of the Cu surface and altered its intrinsic activity for CO2RR. As the potential of the Cu catalyst became more negative, there was an increase in surface iodine anion concentration ([I-]), which could be connected to the reaction-enhanced adsorption of I- ions accompanying the increase in CO2RR activity. A linear relationship was observed between [I-] and current density. SEIRAS results further suggested that the presence of KI in the electrolyte strengthened the Cu-CO bond and facilitated the hydrogenation process, enhancing the production of CH4. Our results have thus provided insight into the role of halogen anions and aided in the design of an efficient CO2RR process.

A Spectroscopic Study on Nitrogen Electrooxidation to Nitrate.

As a potential substitute technique for conventional nitrate production, electrocatalytic nitrogen oxidation reaction (NOR) is gaining more and more attention. But, the pathway of this reaction is still unknown owing to the lack of understanding on key reaction intermediates. Herein, electrochemical in situ attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) and isotope-labeled online differential electrochemical mass spectrometry (DEMS) are employed to study the NOR mechanism over a Rh catalyst. Based on the detected asymmetric NO2- bending, NO3- vibration, N=O stretching, and N-N stretching as well as isotope-labeled mass signals of N2O and NO, it can be deduced that the NOR undergoes an associative mechanism (distal approach) and the strong N≡N bond in N2 prefers to break concurrently with the hydroxyl addition in distal N.

Charge-acquired Pb2+ boosts actively and selectively electrochemical carbon dioxide reduction reaction to formate

For lead carbonate-based (PbCO3) carbon dioxide reduction reaction (CO2RR) electrocatalysts, the electron-deficiency of Pb2+ active sites adverse to activate *CO2 and generate HCOO* intermediates hinder the active and selective CO2RR to formate. In this work, the Co modified (heterojunction and doping) PbCO3 electrocatalyst is constructed with prominent catalytic activity and high formate selectivity (Faradaic efficiency about 98.15% at −0.70 V vs. RHE). The in-depth experimental and theoretical analyses reveal that the Co-PbCO3 interaction can enable the electron of Co transfer to Pb2+, leading to the charge-acquired Pb2+ (CA-Pb2+). Its highly catalytic activity and selectivity of formate is attributed to the reduced formation energy barrier and enhanced adsorption behavior of HCOO* intermediate. The in-situ attenuated total reflection surface-enhanced infrared absorption spectroscopy demonstrates HCOO* intermediate is more likely to generate and adsorb on CA-Pb2+ than Pb2+, verifying the charge acquisition of Pb2+ enhances the activity and selectivity of formate product.

Unraveling the electrocatalytic reduction mechanism of enols on copper in aqueous media

Deoxygenation of aldehydes and their tautomers to alkenes and alkanes has implications in refining biomass-derived fuels for use as transportation fuel. Electrochemical deoxygenation in ambient, aqueous solution is also a potential green synthesis strategy for terminal olefins. In this manuscript, direct electrochemical conversion of vinyl alcohol and acetaldehyde on polycrystalline Cu to ethanol, ethylene and ethane; and propenol and propionaldehyde to propanol, propene and propane is reported. Sensitive detection was achieved using a rotating disk electrode coupled with gas chromatography-mass spectrometry. In-situ attenuated total reflection surface-enhanced infrared absorption spectroscopy, and in-situ Raman spectroscopy confirmed the adsorption of the vinyl alcohol. Calculations using canonical and grand-canonical density functional theory and experimental findings suggest that the rate-determining step for ethylene and ethane formation is an electron transfer step to the adsorbed vinyl alcohol. Finally, we extend our conclusions to the enol reaction from higher-order soluble aldehyde and ketone. The products observed from the reduction reaction also sheds insights into plausible reaction pathways of CO2 to C2 and C3 products.

In Situ Wide-Frequency Surface-Enhanced Infrared Absorption Spectroscopy Enables One to Decipher the Interfacial Structure of a Cu Plating Additive.

In situ spectroscopic characterization of the interfacial structure of an organic additive at a Cu electrode is essential for a mechanistic understanding of Cu superfilling at the molecular level. In this work, we demonstrate wide-frequency attenuated total reflection surface-enhanced infrared absorption spectroscopy (wf-ATR-SEIRAS) to elucidate the dissociative adsorption of bis(sodium sulfopropyl)-disulfide (a typical accelerator) on a Cu electrode in conjunction with the electrochemical quartz crystal microbalance measurement and modeling calculations. The wf-ATR-SEIRAS clearly identifies the peaks featuring the sulfonate and methylene groups as well as the C-Ssulfonate and C-Sthiol vibrations of the adsorbate. Analysis of relative peak intensities from 1100 to 650 cm-1 reveals a more tilted alkyl chain axis for the thiolate on Cu than that on Au, which is supported by comparative density functional theory calculations. This work opens a new avenue for the wf-ATR-SEIRAS to study interfacial structures of electroplating additives related to advanced microelectronics manufacture.

Electrochemical Upgrading of Formic Acid to Formamide via Coupling Nitrite Co-Reduction.

Formic acid (HCOOH) can be exclusively prepared through CO2 electroreduction at an industrial current density (0.5 A cm-2). However, the global annual demand for formic acid is only ∼1 million tons, far less than the current CO2 emission scale. The exploration of an economical and green approach to upgrading CO2-derived formic acid is significant. Here, we report an electrochemical process to convert formic acid and nitrite into high-valued formamide over a copper catalyst under ambient conditions, which offers the selectivity from formic acid to formamide up to 90.0%. Isotope-labeled in situ attenuated total reflection surface-enhanced infrared absorption spectroscopy and quasi in situ electron paramagnetic resonance results reveal the key C-N bond formation through coupling *CHO and *NH2 intermediates. This work offers an electrochemical strategy to upgrade CO2-derived formic acid into high-value formamide.

The PdHx metallene with vacancies for synergistically enhancing electrocatalytic N2 fixation

It is of great significance to controlled synthesis of high activity, selectivity and durable electrocatalysts. In this work, for the first time, the ultrathin (0.9 nm) of interstitial metallene with controlled vacancies and lattice hydrogen atoms are successfully gained. With the optimal lattice hydrogen atoms and composition, the interstitial VPd-PdH0.41 metallene exhibits the great nitrogen reduction (NRR) activity in Li2SO4 solution, among interstitial PdHx with different extent of vacancies, interstitial PdH0.41 without vacancies and Pd nansheets. The density functional theory (DFT), in situ Raman and Attenuated total reflection surface-enhanced infrared absorption spectrum (ATR-SEIRAS) tests further display that the VPd on the interstitial VPd-PdH0.41 metallene can urges the adsorption and arousal of N2, while lattice hydrogen atoms as active hydrogen source to follow an association mechanism rather than a dissociation mechanism, showing nice NRR performance at low overpotential.

Adjusting Local CO Confinement in Porous-Shell Ag@Cu Catalysts for Enhancing C-C Coupling toward CO2 Eletroreduction.

Tuning the local confinement of reaction intermediates is of pivotal significance to promote C-C coupling for enhancing the selectivity for multicarbon (C2+) products toward CO2 electroreduction. Herein, we have gained insights into the confinement effect of local CO concentration for enhanced C-C coupling over core-shell Ag@Cu catalysts by tuning the pore diameters within porous Cu shells. During CO2 electroreduction, the core-shell Ag@Cu catalysts with an average pore diameter of 4.9 nm within the Cu shells (Ag@Cu-p4.9) exhibited the highest Faradaic efficiency of 73.7% for C2+ products at 300 mA cm-2 among the three Ag@Cu catalysts. Finite-element-method simulations revealed that the pores with a diameter of 4.9 nm in Cu conspicuously enhanced the local CO concentration. On the basis of in situ attenuated total reflection surface-enhanced infrared absorption spectroscopy measurements, Ag@Cu-p4.9 exhibited the highest surface coverage of adsorbed CO intermediates with a linear adsorption configuration due to the confinement effect, thus facilitating C-C coupling.