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Abstract: High‐aspect‐ratio silicon microwire (Si MW) arrays are expected to act as potential absorbers for solar energy conversion due to their excellent optically absorption capability and shorter diffusion length for collecting charge carriers. To date, most of the studies on structured Si microwire arrays devices are focusing on photocathode for the photoelectrochemical hydrogen production, only a handful of reports attempt to use photoanode based on Si microwire arrays for water oxidation. Herein, a tunable electrodeposition technique for decorating isolated Ni nanoparticles as a both protecting and oxygen evolution electrocatalyst onto the n‐type Si MW is demonstrated. The Si microwire array photoanodes with optimized surface decoration show a stable photocurrent density of 10 mA cm−2 in 1 m KOH electrolyte for several hours without additional protecting layer in addition to Ni nanoparticles, in which the optimized photoanode is able to produce a maximum photocurrent density of 35.5 mA cm−2. [ABSTRACT FROM AUTHOR]

Surface-enhanced Raman scattering (SERS) utilizing the well-defined localized surface plasmon resonance (LSPR) of Ag and Au nanoparticles (NPs) under resonant irradiation has emerged as a promising spectroscopy technique for providing vibrational information on trace molecules. The Raman scattering intensity from molecules close to the surface of these finely divided metals can be significantly enhanced by a factor of more than 106. In addition to the high sensitivity, the reproducibility of the SERS signal is also an important parameter for its reliable application. In this work, we report on the innovative and facile fabrication of a Au NP-decorated SiO2 mask coated on indium tin oxide (ITO) glass as a SERS array substrate. First, a highly ordered porous SiO2 mask with pore sizes of 350 nm in diameter and wall thickness of 60 nm was deposited on ITO glass by using spin coating. Then, Au NPs were controllably decorated into the pores of the conductive ITO glass-bottomed SiO2 mask by using sonoelectrochemical deposition–dissolution cycling (SEDDC). Experimental results indicate that the SERS effect of Rhodamine 6G (R6G) observed on this developed substrate increases with an increase in the deposition time of Au NPs in SEDDC. The corresponding optimal enhancement factor (EF) that is obtained is ca. 6.5 × 107. Significantly, this system achieves an optimal reproducibility under a medium-length deposition time of Au NPs in SEDDC with a relative standard deviation (RSD) of 12% for measurements of five spots on different areas. The low RSD of the SERS signal and the large EF suggest that the developed array system can serve as an excellent spectroscopy platform for practical applications in analytical chemistry. [ABSTRACT FROM AUTHOR]

Lithium‐carbon dioxide (Li‐CO2) and Li‐air batteries hold great potential in achieving carbon neutral given their ultrahigh theoretical energy density and eco‐friendly features. However, these Li‐gas batteries still suffer from low discharging‐charging rate and poor cycling life due to sluggish decomposition kinetics of discharge products especially Li2CO3. Here we report the theory‐guided design and preparation of unconventional phase metal heteronanostructures as cathode catalysts for high‐performance Li‐CO2/air batteries. The assembled Li‐CO2 cells with unconventional phase 4H/face‐centered cubic (fcc) ruthenium‐nickel heteronanostructures deliver a narrow discharge‐charge gap of 0.65 V, excellent rate capability and long‐term cycling stability over 200 cycles at 250 mA g−1. The constructed Li‐air batteries can steadily run for above 150 cycles in ambient air. Electrochemical mechanism studies reveal that 4H/fcc Ru−Ni with high‐electroactivity facets can boost redox reaction kinetics and tune discharge reactions towards Li2C2O4 path, alleviating electrolyte/catalyst failures induced by the aggressive singlet oxygen from solo decomposition of Li2CO3. [ABSTRACT FROM AUTHOR]

The interaction between oxygen species and metal sites of various orbitals exhibits intimate correlation with the oxygen reduction reaction (ORR) kinetics. Herein, a new approach for boosting the inherent ORR activity of atomically dispersed Fe-N-C matrix is represented by implanting Fe atomic clusters nearby. The as-prepared catalyst delivers excellent ORR activity with half-wave potentials of 0.78 and 0.90 V in acidic and alkaline solutions, respectively. The decent ORR activity can also be validated from the high-performance rechargeable Zn-air battery. The experiments and density functional theory calculations reveal that the electron spin-state of monodispersed Fe active sites is transferred from the low spin (LS, t 2g 6 e g 0 ) to the medium spin (MS, t 2g 5 e g 1 ) due to the involvement of Fe atomic clusters, leading to the spin electron filling in σ∗ orbit, by which it favors OH - desorption and in turn boosts the reaction kinetics of the rate-determining step. This work paves a solid way for rational design of high-performance Fe-based single atom catalysts through spin manipulation., (© 2024 Wiley‐VCH GmbH.)

The development of facile, efficient synthesis method to construct low-cost and high-performance single-atom catalysts (SACs) for oxygen reduction reaction (ORR) is extremely important, yet still challenging. Herein, an atomically dispersed N, S co-doped carbon with abundant vacancy defects (NSC-vd) anchored Fe single atoms (SAs) is reported and a vacancy defects inductive effect is proposed for promoting electrocatalytic ORR. The optimized catalyst featured of stable Fe─N 3 S 1 active sites exhibits excellent ORR activity with high turnover frequency and mass activity. In situ Raman, attenuated total reflectance surface enhanced infrared absorption spectroscopy reveal the Fe─N 3 S 1 active sites exhibit different kinetic mechanisms in acidic and alkaline solutions. Operando X-ray absorption spectra reveal the ORR activity of Fe SAs/NSC-vd catalyst in different electrolyte is closely related to the coordination structure. Theoretical calculation reveals the upshifted d band center of Fe─N 3 S 1 active sites facilitates the adsorption of O 2 and accelerates the kinetics process of *OH reduction. The abundant vacancy defects around the Fe─N 3 S 1 active sites balance the OOH* formation and *OH reduction, thus synergetically promoting the electrocatalytic ORR process., (© 2023 Wiley-VCH GmbH.)

Photocatalytic organic functionalization reactions represent a green, cost-effective, and sustainable synthesis route for value-added chemicals. However, heterogeneous photocatalysis is inefficient in directly activating ammonia molecules for the production of high-value-added nitrogenous organic products when compared with oxygen activation in the formation of related oxygenated compounds. In this study, we report the heterogeneous photosynthesis of benzonitriles by the ammoxidation of benzyl alcohols (99 % conversion, 93 % selectivity) promoted using BiOBr nanosheets with surface vacancy associates. In contrast, the main reaction of catalysts with other types of vacancy sites is the oxidation of benzyl alcohol to benzaldehyde or benzoic acid. Experimental measurements and theoretical calculations have demonstrated a specificity of vacancy type with respect to product selectivity, which arises from the adsorption and activation of NH 3 and O 2 that is required to promote subsequent C-N coupling and oxidation to nitrile. This study provides a better understanding of the role of vacancies as catalytic sites in heterogeneous photocatalysis., (© 2023 Wiley-VCH GmbH.)

Multimetallic alloy nanoparticles (NPs) have received considerable attention in various applications due to their compositional variability and exceptional properties. However, the complexity of both the general synthesis and structure-activity relationships remain the long-standing challenges in this field. Herein, we report a versatile 2D MOF-assisted pyrolysis-displacement-alloying route to successfully synthesize a series of binary, ternary and even high-entropy NPs that are uniformly dispersed on porous nitrogen-doped carbon nanosheets (PNC NSs). As a proof of utility, the obtained Co 0.2 Ru 0.7 Pt 0.1 /PNC NSs exhibits apparent hydrogen oxidation activity and durability with a record-high mass specific kinetic current of 1.84 A mg -1 at the overpotential of 50 mV, which is approximately 11.5 times higher than that of the Pt benchmark. Both experimental and theoretical studies reveal that the addition of Pt engenders a phase transition in CoRu alloys from hexagonal close-packed (hcp) to face-centered cubic (fcc) structure. The elevated reactivity of the resulted ternary alloy can be attributed to the optimized adsorption of hydrogen intermediate and the decreased reaction barrier for water formation. This study opens a new avenue for the development of highly efficient alloy NPs with various compositions and functions., (© 2023 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

This study adopts a facile and effective in situ encapsulation-oxidation strategy for constructing a coupling catalyst composed of atomically dispersed Pt-doped Co 3 O 4 spinel nanoparticles (NPs) embedded in polyhedron frames (PFs) for robust propane total oxidation. Benefiting from the abundant oxygen vacancies and more highly valent active Co 3+ species caused by the doping of Pt atoms as well as the confinement effect, the optimized 0.2Pt-Co 3 O 4 NPs/PFs catalyst exhibits excellent propane catalytic activity with low T 90 (184 °C), superior apparent reaction rate (21.62×10 8 (mol g cat -1 s -1 )), low apparent activation energy (E a = 17.89 kJ mol -1 ), high turnover frequency ( 811×10 7 (mol g cat -1 s -1 )) as well as good stability. In situ diffuse reflectance infrared Fourier transform spectroscopy and density functional theory calculations indicate that the doping of Pt atoms enhances the oxygen activation ability, and decreases the energy barrier required for CH bond breaking, thus improving the deep oxidation process of the intermediate species. This study opens up new ideas for constructing coupling catalysts from atomic scale with low cost to enhance the activation of oxygen molecules and the deep oxidation of linear short chain alkanes at low temperature., (© 2023 Wiley-VCH GmbH.)

Copper-oxide electrocatalysts have been demonstrated to effectively perform the electrochemical CO 2 reduction reaction (CO 2 RR) toward C 2+ products, yet preserving the reactive high-valent CuO x has remained elusive. Herein, we demonstrate a model system of Lewis acidic supported Cu electrocatalyst with a pulsed electroreduction method to achieve enhanced performance for C 2+ products, in which an optimized electrocatalyst could reach ∼76% Faradaic efficiency for C 2+ products (FE C 2+ ) at ∼-0.99 V versus reversible hydrogen electrode, and the corresponding mass activity can be enhanced by ∼2 times as compared to that of conventional CuO x . In situ time-resolved X-ray absorption spectroscopy investigating the dynamic chemical/physical nature of Cu during CO 2 RR discloses that an activation process induced by the KOH electrolyte during pulsed electroreduction greatly enriched the Cu δ+ O/Zn δ+ O interfaces, which further reveals that the presence of Zn δ+ O species under the cathodic potential could effectively serve as a Lewis acidic support for preserving the Cu δ+ O species to facilitate the formation of C 2+ products, and the catalyst structure-property relationship of Cu δ+ O/Zn δ+ O interfaces can be evidently realized. More importantly, we find a universality of stabilizing Cu δ+ O species for various metal oxide supports and to provide a general concept of appropriate electrocatalyst-Lewis acidic support interaction for promoting C 2+ products.

Unravelling the dynamic characterization of electrocatalysts during the electrochemical CO 2 reduction reaction (CO 2 RR) is a critical factor to improve the production efficiency and selectivity, since most pre-electrocatalysts undergo structural reconstruction and surface rearrangement under working conditions. Herein, a series of pre-electrocatalysts including CuO, ZnO and two different ratios of CuO/ZnO were systematically designed by a sputtering process to clarify the correlation of the dynamic characterization of Cu sites in the presence of Zn/ZnO and the product profile. The evidence provided by in situ X-ray absorption spectroscopy (XAS) indicated that appropriate Zn/ZnO levels could induce a variation in the coordination number of Cu sites via reversing Ostwald ripening. Specifically, the recrystallized Cu site with a lower coordination number exhibited a preferential production of methane (CH 4 ). More importantly, our findings provide a promising approach for the efficient production of CH 4 by in situ reconstructing Cu-based binary electrocatalysts.

The adsorption and desorption of electrolyte ions strongly modulates the carrier density or carrier type on the surface of monolayer-MoS 2 catalyst during the hydrogen evolution reaction (HER). The buildup of electrolyte ions onto the surface of monolayer MoS 2 during the HER may also result in the formation of excitons and trions, similar to those observed in gate-controlled field-effect transistor devices. Using the distinct carrier relaxation dynamics of excitons and trions of monolayer MoS 2 as sensitive descriptors, an in situ microcell-based scanning time-resolved liquid cell microscope is set up to simultaneously measure the bias-dependent exciton/trion dynamics and spatially map the catalytic activity of monolayer MoS 2 during the HER. This operando probing technique used to monitor the interplay between exciton/trion dynamics and electrocatalytic activity for two-dimensional transition metal dichalcogenides provides an excellent platform to investigate the local carrier behaviors at the atomic layer/liquid electrolyte interfaces during electrocatalytic reaction.

Real bifunctional electrocatalysts for hydrogen evolution reaction and oxygen evolution reaction have to be the ones that exhibit a steady configuration during/after reaction without irreversible structural transformation or surface reconstruction. Otherwise, they can be termed as "precatalysts" rather than real catalysts. Herein, through a strongly atomic metal-support interaction, single-atom dispersed catalysts decorating atomically dispersed Ru onto a nickel-vanadium layered double hydroxide (LDH) scaffold can exhibit excellent HER and OER activities. Both in situ X-ray absorption spectroscopy and operando Raman spectroscopic investigation clarify that the presence of atomic Ru on the surface of nickel-vanadium LDH is playing an imperative role in stabilizing the dangling bond-rich surface and further leads to a reconstruction-free surface. Through strong metal-support interaction provided by nickel-vanadium LDH, the significant interplay can stabilize the reactive atomic Ru site to reach a small fluctuation in oxidation state toward cathodic HER without reconstruction, while the atomic Ru site can stabilize the Ni site to have a greater structural tolerance toward both the bond constriction and structural distortion caused by oxidizing the Ni site during anodic OER and boost the oxidation state increase in the Ni site that contributes to its superior OER performance. Unlike numerous bifunctional catalysts that have suffered from the structural reconstruction/transformation for adapting the HER/OER cycles, the proposed Ru/Ni 3 V-LDH is characteristic of steady dual reactive sites with the presence of a strong metal-support interaction (i.e., Ru and Ni sites) for individual catalysis in water splitting and is revealed to be termed as a real bifunctional electrocatalyst.

To reach a carbon-neutral future, electrochemical CO 2 reduction reaction (eCO 2 RR) has proven to be a strong candidate for the next-generation energy system. Among potential materials, single-atom catalysts (SACs) serve as a model to study the mechanism behind the reduction of CO 2 to CO, given their well-defined active metal centers and structural simplicity. Moreover, using metal-organic frameworks (MOFs) as supports to anchor and stabilize central metal atoms, the common concern, metal aggregation, for SACs can be addressed well. Furthermore, with their turnability and designability, MOF-derived SACs can also extend the scope of research on SACs for the eCO 2 RR. Herein, we synthesize sulfurized MOF-derived Mn SACs to study effects of the S dopant on the eCO 2 RR. Using complementary characterization techniques, the metal moiety of the sulfurized MOF-derived Mn SACs (Mn SA /SNC) is identified as MnN 3 S 1 . Compared with its non-sulfur-modified counterpart (Mn SA /NC), the Mn SA /SNC provides uniformly superior activity to produce CO. Specifically, a nearly 30% enhancement of Faradaic efficiency (F.E.) in CO production is observed, and the highest F.E. of approximately 70% is identified at -0.45 V. Through operando spectroscopic characterization, the probing results reveal that the overall enhancement of CO production on the Mn SA /SNC is possibly caused by the S atom in the local MnN 3 S 1 moiety, as the sulfur atom may induce the formation of S-O bonding to stabilize the critical intermediate, *COOH, for CO 2 -to-CO. Our results provide novel design insights into the field of SACs for the eCO 2 RR.

Unraveling the reaction mechanism behind the CO 2 reduction reaction (CO 2 RR) is a crucial step for advancing the development of efficient and selective electrocatalysts to yield valuable chemicals. To understand the mechanism of zinc electrocatalysts toward the CO 2 RR, a series of thermally oxidized zinc foils is prepared to achieve a direct correlation between the chemical state of the electrocatalyst and product selectivity. The evidence provided by in situ Raman spectroscopy, X-ray absorption spectroscopy (XAS) and X-ray diffraction significantly demonstrates that the Zn(ii) and Zn(0) species on the surface are responsible for the production of carbon monoxide (CO) and formate, respectively. Specifically, the destruction of a dense oxide layer on the surface of zinc foil through a thermal oxidation process results in a 4-fold improvement of faradaic efficiency (FE) of formate toward the CO 2 RR. The results from in situ measurements reveal that the chemical state of zinc electrocatalysts could dominate the product profile for the CO 2 RR, which provides a promising approach for tuning the product selectivity of zinc electrocatalysts.

Understanding the dynamic structural reconstruction/transformation of catalysts during electrochemical CO 2 reduction reaction (CO 2 RR) is highly desired for developing more efficient and selective catalysts, yet still lacks in-depth realization. Herein, we study a model system of copper nanowires with various degrees of silver modifications as electrocatalysts for CO 2 RR. Among them, the Cu 68 Ag 32 nanowire catalyst achieves the highest activity and selectivity toward methane with an extremely high faradaic efficiency of ∼60%, about 3 times higher than that of primitive Cu nanowires, and even surpasses the most efficient catalysts for producing methane. By using in situ grazing-angle X-ray scattering/diffraction, X-ray absorption spectroscopy, and Raman techniques, we found that the Cu 68 Ag 32 nanowires underwent an irreversible structural reconstruction and well-stabilized chemical state of Cu on the catalyst surface under the working CO 2 RR conditions, which greatly facilitates the CO 2 to methane conversion. Further analysis reveals that the restructuring phenomenon can be ascribed to a reoxidation/reduction-driven atomic interdiffusion between Cu and Ag. This work reveals the first empirical demonstration by deploying comprehensive in situ techniques to track the dynamic structural reconstruction/transformation in a model bimetallic system, which not only establishes a good understanding of the correlation between catalyst surface structure and catalytic selectivity but also provides deep insights into designing more developed electrocatalysts for CO 2 RR and beyond.

Oxide-derived copper catalysts have been shown to enhance CO 2 reduction reaction (CO 2 RR) activity with high selectivity toward hydrocarbon products. However, the chemical state of oxide-derived copper during the CO 2 RR has remained elusive and is lacking in situ observations. Herein, a two-step process was developed to synthesize Ag nanowires coated with various thicknesses of a CuO x layer for the CO 2 RR. By employing in situ X-ray absorption spectroscopy, a strong correlation between the chemical state under reaction conditions and the CO 2 RR product profile can be revealed to validate another competing reaction (i.e., the spontaneous oxidation of Cu(0) in aqueous electrolyte) that significantly governs the chemical state of active centers of Cu. In situ Raman spectroscopy reveals the existence of reoxidation behavior under cathodic potential, and the quantification analysis of reoxidized behavior is revealed to indicate that the reoxidation rate is independent of surface morphology and strongly proportional to the electrochemically surface area. The steady oxidation state of Cu in an in situ condition is the paramount key and dominates the products' profile of the CO 2 RR rather than other factors (e.g., crystal facets, atomic arrangements, morphology, elements) that have been investigated in numerous reports., Competing Interests: The authors declare no competing financial interest., (Copyright © 2019 American Chemical Society.)

Roughing the metallic surface via oxidation-reduction cycles (ORC) to integrate the surface plasmon resonance and surface-enhanced Raman scattering (SERS) is predominant in developing sensor systems because of the facile preparation and uniform distribution of nanostructures. Herein, we proposed a distinctive ORC process: the forward potential passed through the oxidation of Au and reached the oxygen evolution reaction, and once the potential briefly remained at the vertex, the various reverse rates were employed to control the reduction state. The created hybrid Au-AuO x possessed electromagnetic and chemical enhancements concurrently, wherein the rough surface provided the strong local electromagnetic fields and significant interaction between AuO x and molecule to improve the charge transfer. The synergistic effects significantly amplified the intensity of Raman signal with an enhancement factor of 5.5 × 10 6 under the optimal conditions. Furthermore, the prepared SERS substrate can simultaneously identify and quantify the mixed edible pigments, Brilliant Blue FCF and Indigo Carmine, individually. This result suggested that the development of SERS sensor based on the proposed SERS-activated methodology is feasible and reliable., Competing Interests: The authors declare no competing financial interest.

Interesting properties of water with distinguishable hydrogen-bonding structure on interfacial phase or in confined environment have drawn wide attentions. However, these unique properties of water are only found within the interfacial phase and confined environment, thus, their applications are limited. In addition, quantitative evaluation on these unique properties associating with the enhancement of water's physical and chemical activities represents a notable challenge. Here we report a practicable production of free-standing liquid water at room temperature with weak hydrogen-bonded structure naming Au nanoparticles (NPs)-treated (AuNT) water via treating by plasmon-induced hot electron transfer occurred on resonantly illuminated gold NPs (AuNPs). Compared to well-known untreated bulk water (deionized water), the prepared AuNT water exhibits many distinct activities in generally physical and chemical reactions, such as high solubilities to NaCl and O2. Also, reducing interaction energy within water molecules provides lower overpotential and higher efficiency in electrolytic hydrogen production. In addition, these enhanced catalytic activities of AuNT water are tunable by mixing with deionized water. Also, most of these tunable activities are linearly proportional to its degree of nonhydrogen-bonded structure (DNHBS), which is derived from the O-H stretching in deconvoluted Raman spectrum.