KIr4O8 Nanowires with Rich Hydroxyl Promote Oxygen Evolution Reaction in Proton Exchange Membrane Water Electrolyzer.

The sluggish kinetics for anodic oxygen evolution reaction (OER) and insufficient catalytic performance over the corresponding Ir-based catalysts are still enormous challenges in proton exchange membrane water electrolyzer (PEMWE). Herein, we report that KIr4O8 nanowires anode catalyst with more exposed active sites and rich hydroxyl achieves a current density of 1.0 A/cm2 at 1.68 V and possesses excellent catalytic stability with 1230 h in PEMWE. Combining in situ Raman spectroscopy and differential electrochemical mass spectroscopy results, we propose the modified adsorbate evolution mechanism that rich hydroxyl in the inherent structure of KIr4O8 nanowires directly participates in the catalytic process for favoring the OER. Density functional theory calculation results further suggest that the enhanced proximity between Ir (d) and O (p) band center in KIr4O8 can strengthen the covalence of Ir-O, facilitate the electron transfer between adsorbents and active sites, and decrease the energy barrier of rate-determining step from OH* to O* during the OER. This article is protected by copyright. All rights reserved.

In Situ Self-Assembled Active and Stable Ir@MnOx/La0.7Sr0.3Cr0.9Ir0.1O3-δ Interfaces for CO2 Electrolysis.

Solid oxide electrolysis cells are prospective approaches for CO2 utilization but face significant challenges due to the sluggish reaction kinetics and poor stability of the fuel electrodes. Herein, we strategically addressed the long-standing trade-off phenomenon between enhanced exsolution and improved structural stability via topotactic ion exchange. The surface dynamic reconstruction of the MnOx/La0.7Sr0.3Cr0.9Ir0.1O3-δ (LSCIr) catalyst was visualized at the atomic scale. Compared with the Ir@LSCIr interface, the in situ self-assembled Ir@MnOx/LSCIr interface exhibited greater CO2 activation and easily removable carbonate intermediates, thus reached a 42% improvement in CO2 electrolysis performance at 1.6 V. Furthermore, an improved CO2 electrolysis stability was achieved due to the uniformly wrapped MnOx shell of the Ir@MnOx/LSCIr cathode. Our approach enables a detailed understanding of the dynamic microstructure evolution at active interfaces and provides a roadmap for the rational design and evaluation of efficient metal/oxide catalysts for CO2 electrolysis.

Boosting Electrocatalytic Ethylene Epoxidation by Single Atom Modulation.

The electrochemical synthesis of ethylene oxide (EO) using ethylene and water under ambient conditions presents a low-carbon alternative to existing industrial production process. Yet, the electrocatalytic ethylene epoxidation route is currently hindered by largely insufficient activity, EO selectivity, and long-term stability. Here we report a single atom Ru-doped hollandite structure KIr4O8 (KIrRuO) nanowire catalyst for efficient EO production via a chloride-mediated ethylene epoxidation process. The KIrRuO catalyst exhibits an EO partial current density up to 0.7 A cm-2 and an EO yield as high as 92.0 %. The impressive electrocatalytic performance towards ethylene epoxidation is ascribed to the modulation of electronic structures of adjacent Ir sites by single Ru atoms, which stabilizes the *CH2CH2OH intermediate and facilitates the formation of active Cl2 species during the generation of 2-chloroethanol, the precursor of EO. This work provides a single atom modulation strategy for improving the reactivity of adjacent metal sites in heterogeneous electrocatalysts.

Durable CO2 conversion in the proton-exchange membrane system.

Electrolysis that reduces carbon dioxide (CO2) to useful chemicals can, in principle, contribute to a more sustainable and carbon-neutral future1-6. However, it remains challenging to develop this into a robust process because efficient conversion typically requires alkaline conditions in which CO2 precipitates as carbonate, and this limits carbon utilization and the stability of the system7-12. Strategies such as physical washing, pulsed operation and the use of dipolar membranes can partially alleviate these problems but do not fully resolve them11,13-15. CO2 electrolysis in acid electrolyte, where carbonate does not form, has therefore been explored as an ultimately more workable solution16-18. Herein we develop a proton-exchange membrane system that reduces CO2 to formic acid at a catalyst that is derived from waste lead-acid batteries and in which a lattice carbon activation mechanism contributes. When coupling CO2 reduction with hydrogen oxidation, formic acid is produced with over 93% Faradaic efficiency. The system is compatible with start-up/shut-down processes, achieves nearly 91% single-pass conversion efficiency for CO2 at a current density of 600 mA cm-2 and cell voltage of 2.2 V and is shown to operate continuously for more than 5,200 h. We expect that this exceptional performance, enabled by the use of a robust and efficient catalyst, stable three-phase interface and durable membrane, will help advance the development of carbon-neutral technologies.

Surface Activation by Single Ru Atoms for Enhanced High-Temperature CO2 Electrolysis.

Cathodic CO2 adsorption and activation is essential for high-temperature CO2 electrolysis in solid oxide electrolysis cells (SOECs). However, the component of oxygen ionic conductor in the cathode displays limited electrocatalytic activity. Herein, stable single Ruthenium (Ru) atoms are anchored on the surface of oxygen ionic conductor (Ce0.8 Sm0.2 O2-δ , SDC) via the strong covalent metal-support interaction, which evidently modifies the electronic structure of SDC surface for favorable oxygen vacancy formation and enhanced CO2 adsorption and activation, finally evoking the electrocatalytic activity of SDC for high-temperature CO2 electrolysis. Experimentally, SOEC with the Ru1 /SDC-La0.6 Sr0.4 Co0.2 Fe0.8 O3-δ cathode exhibits a current density as high as 2.39 A cm-2 at 1.6 V and 800 °C. This work expands the application of single atom catalyst to the high-temperature electrocatalytic reaction in SOEC and provides an efficient strategy to tailor the electronic structure and electrocatalytic activity of SOEC cathode at the atomic scale.

Sulfurized NiFe2 O4 Electrocatalyst with In Situ Formed Fe-NiOOH Nanoparticles to Realize Industrial-Level Oxygen Evolution.

Constructing composite catalysts with refined geometric control and optimal electronic structure provides a promising route to enhance electrocatalytic performance toward the oxygen evolution reaction (OER). Herein, a composite catalyst is prepared with multiple components using chemical vapour deposition method to transform crystalline NiFe2 O4 into crystalline NiFe2 O4 @amorphous S-NiFe2 O4 with core-shell structure (C-NiFe2 O4 @A-S-NiFe2 O4 ), and Fe-NiOOH nanoparticles are subsequently in situ generated on its surface during the process of electrocatalytic OER. The C-NiFe2 O4 @A-S-NiFe2 O4 catalyst exhibits a low overpotential of 275 mV while possessing an excellent stability for 500 h at 10 mA cm-2 . The anion exchange membrane water electrolyzer with C-NiFe2 O4 @A-S-NiFe2 O4 anode catalyst obtains a current density of 4270 mA cm- 2 at 2.0 V. Further, in situ Raman spectroscopy result demonstrates that in situ generated Fe-NiOOH nanoparticles are revealed to act as the catalytic active phase for catalyzing the OER. Besides, introducing A-S-NiFe2 O4 in C-NiFe2 O4 @A-S-NiFe2 O4 facilitates the formation of Fe-NiOOH nanoparticles with high-valency Ni, thus increasing the proportion of lattice oxygen-participated OER. This work not only provides an alternative strategy for the design of high-performance catalysts, but also lays a foundation for the exploration of catalytic mechanisms.

Insights into the mechanism in electrochemical CO2 reduction over single-atom copper alloy catalysts: A DFT study.

Copper single-atom alloy catalysts (M@Cu SAAs) have shown great promise for electrochemical CO2 reduction reaction (CO2RR). However, a clear understanding of the CO2RR process on M@Cu SAAs is still lacking. This study uses density functional theoretical (DFT) calculations to obtain a comprehensive mechanism and the origin of activity of M@Cu SAAs. The importance of the adsorption mode of M@Cu is revealed: key intermediates either adsorbed in the adjacent hollow site around Cu atoms (AD mode) or adsorbed directly on the top site of M (SE mode). AD mode generally exhibits finely tuned binding strengths of key intermediates, which significantly enhances the activity of the catalysts. Increasing the coverage of ∗CO on the M@Cu with SE mode leads to relocation of the active site, resulting in improved activity of C2 products. The insights gained in this work have significant implications for rational design strategy toward efficient CO2RR electrocatalysts.

A comparative analysis of quantitative detection methods for viable food-borne pathogens using RT-qPCR and PMA-qPCR.

The accurate quantification of viable pathogens in food is crucial for ensuring food safety. This study mainly aimed to investigate the quantification of viable pathogens using PMA-qPCR and RT-qPCR, taking into account bacterial species, food matrices, and inactivation methods. The detection limit of PMA-qPCR for Salmonella serovars in simple matrices, such as culture broth, lake, or tap water, was found to be 102 cells per ml. Regarding the detection of Staphylococcus aureus and Escherichia coli in culture broth, as well as Salmonella in more complex matrices, such as juices and lab-made broth, both methods exhibited a detection limit of 103 cells per ml. Besides that, in adverse situations, there was a risk of overestimating the number of viable pathogens using PMA-qPCR. In addition, a conspicuous discrepancy between the results of PMA-qPCR/RT-qPCR and those of the plate counting assay was observed when Salmonella was exposed to isopropanol, H2O2, NaClO, sonication, or thermosonication. This suggests that it may survive in a viable but non-culturable state and poses a challenge for accurate quantification of viable cells using plate counting assay. Therefore, the results obtained by RT-qPCR were more objective compared to PMA-qPCR due to potential influences from bacteria species, surrounding media, and inactivation methods.

Directing the Selectivity of CO Electrolysis to Acetate by Constructing Metal-Organic Interfaces.

Electrochemically converting CO2 to valuable chemicals holds great promise for closing the anthropogenic carbon cycle. Owing to complex reaction pathways and shared rate-determining steps, directing the selectivity of CO2 /CO electrolysis to a specific multicarbon product is very challenging. We report here a strategy for highly selective production of acetate from CO electrolysis by constructing metal-organic interfaces. We demonstrate that the Cu-organic interfaces constructed by in situ reconstruction of Cu complexes show very impressive acetate selectivity, with a high Faradaic efficiency of 84.2 % and a carbon selectivity of 92.1 % for acetate production, in an alkaline membrane electrode assembly electrolyzer. The maximum acetate partial current density and acetate yield reach as high as 605 mA cm-2 and 63.4 %, respectively. Thorough structural characterizations, control experiments, operando Raman spectroscopy measurements, and density functional theory calculation results indicate that the Cu-organic interface creates a favorable reaction microenvironment that enhances *CO adsorption, lowers the energy barrier for C-C coupling, and facilitates the formation of CH3 COOH over other multicarbon products, thus rationalizing the selective acetate production.

In situ electrochemical reconstruction of Sr2Fe1.45Ir0.05Mo0.5O6-δ perovskite cathode for CO2 electrolysis in solid oxide electrolysis cells.

Solid oxide electrolysis cells provide a practical solution for the direct conversion of CO2 to other chemicals (i.e. CO), however, an in-depth mechanistic understanding of the dynamic reconstruction of active sites for perovskite cathodes during CO2 electrolysis remains a great challenge. Herein, we identify that iridium-doped Sr2Fe1.45Ir0.05Mo0.5O6-δ (SFIrM) perovskite displays a dynamic electrochemical reconstruction feature during CO2 electrolysis with abundant exsolution of highly dispersed IrFe alloy nanoparticles on the SFIrM surface. The in situ reconstructed IrFe@SFIrM interfaces deliver a current density of 1.46 A cm-2 while maintaining over 99% CO Faradaic efficiency, representing a 25.8% improvement compared with the Sr2Fe1.5Mo0.5O6-δ counterpart. In situ electrochemical spectroscopy measurements and density functional theory calculations suggest that the improved CO2 electrolysis activity originates from the facilitated formation of carbonate intermediates at the IrFe@SFIrM interfaces. Our work may open the possibility of using an in situ electrochemical poling method for CO2 electrolysis in practice.

Tuning C1 /C2 Selectivity of CO2 Electrochemical Reduction over in-Situ Evolved CuO/SnO2 Heterostructure.

Heterostructured oxides with versatile active sites, as a class of efficient catalysts for CO2 electrochemical reduction (CO2 ER), are prone to undergo structure reconstruction under working conditions, thus bringing challenges to understanding the reaction mechanism and rationally designing catalysts. Herein, we for the first time elucidate the structural reconstruction of CuO/SnO2 under electrochemical potentials and reveal the intrinsic relationship between CO2 ER product selectivity and the in situ evolved heterostructures. At -0.85 VRHE , the CuO/SnO2 evolves to Cu2 O/SnO2 with high selectivity to HCOOH (Faradaic efficiency of 54.81 %). Mostly interestingly, it is reconstructed to Cu/SnO2-x at -1.05 VRHE with significantly improved Faradaic efficiency to ethanol of 39.8 %. In situ Raman spectra and density functional theory (DFT) calculations reveal that the synergetic absorption of *COOH and *CHOCO intermediates at the interface of Cu/SnO2-x favors the formation of *CO and decreases the energy barrier of C-C coupling, leading to high selectivity to ethanol.

Tailoring Ion Ordering in Perovskite Oxide for High-Temperature Oxygen Evolution Reaction.

Perovskites exhibit excellent high-temperature oxygen evolution reaction (OER) activities as the anodes of solid oxide electrolysis cells (SOECs). However, the relationship between ion ordering and OER performances is rarely investigated. Herein, a series of PrBaCo2-x Fex O5+δ perovskites with tailored ion orderings are constructed. Physicochemical characterizations and density functional theory calculations confirm that the oxygen bulk migration and surface transport capacities as well as the OER activities are promoted by the A-site cation ordering, but weakened by the oxygen vacancy ordering. Hence, SOEC with the A-site-ordered and oxygen-vacancy-disordered PrBaCo2 O5+δ anode exhibits the highest performance of 3.40 A cm-2 at 800 °C and 2.0 V. This work sheds light on the critical role of ion orderings in the high-temperature OER performance and paves a new way for screening novel anode materials of SOECs.

Enhancing Electrochemical Nitrate Reduction to Ammonia over Cu Nanosheets via Facet Tandem Catalysis.

Electrochemical conversion of nitrate (NO3 - ) into ammonia (NH3 ) represents a potential way for achieving carbon-free NH3 production while balancing the nitrogen cycle. Herein we report a high-performance Cu nanosheets catalyst which delivers a NH3 partial current density of 665 mA cm-2 and NH3 yield rate of 1.41 mmol h-1 cm-2 in a flow cell at -0.59 V vs. reversible hydrogen electrode. The catalyst showed a high stability for 700 h with NH3 Faradaic efficiency of ≈88 % at 365 mA cm-2 . In situ spectroscopy results verify that Cu nanosheets are in situ derived from the as-prepared CuO nanosheets under electrochemical NO3 - reduction reaction conditions. Electrochemical measurements and density functional theory calculations indicate that the high performance is attributed to the tandem interaction of Cu(100) and Cu(111) facets. The NO2 - generated on the Cu(100) facets is subsequently hydrogenated on the Cu(111) facets, thus the tandem catalysis promotes the crucial hydrogenation of *NO to *NOH for NH3 production.

The Role of Interfacial Water in CO2 Electrolysis over Ni-N-C Catalyst in a Membrane Electrode Assembly Electrolyzer.

CO2 electrolysis is a promising route for achieving net-zero emission through decarbonization. To realize CO2 electrolysis toward practical application, beyond catalyst structures, it is also critical to rationally manipulate catalyst microenvironments such as the water at the electrode/electrolyte interface. Here, the role of interfacial water in CO2 electrolysis over Ni-N-C catalyst modified with different polymers is investigated. Benefiting from a hydrophilic electrode/electrolyte interface, the Ni-N-C catalyst modified with quaternary ammonia poly(N-methyl-piperidine-co-p-terphenyl) shows a Faradaic efficiency of 95% and a partial current density of 665 mA cm-2 for CO production in an alkaline membrane electrode assembly electrolyzer. A scale-up demonstration using a 100 cm2 electrolyzer achieves a CO production rate of 514 mL min-1 at a current of 80 A. In-situ microscopy and spectroscopy measurements indicate that the hydrophilic interface significantly promotes the formation of the *COOH intermediate, rationalizing the high CO2 electrolysis performance.

Editorial.

Surface and interface engineering has been considered as a promising strategy to enhance the performance of catalysts towards CO2 reduction. In their editorial to this special collection, guest editors Zhicheng Zhang, Zhen Zhang, Zhenyu Sun, Shaoqi Zhan and Guoxiong Wang provide a brief overview of this field and highlight the state-of-the-art contributions featured in this special collection.

Coverage-driven selectivity switch from ethylene to acetate in high-rate CO2/CO electrolysis.

Tuning catalyst microenvironments by electrolytes and organic modifications is effective in improving CO2 electrolysis performance. An alternative way is to use mixed CO/CO2 feeds from incomplete industrial combustion of fossil fuels, but its effect on catalyst microenvironments has been poorly understood. Here we investigate CO/CO2 co-electrolysis over CuO nanosheets in an alkaline membrane electrode assembly electrolyser. With increasing CO pressure in the feed, the major product gradually switches from ethylene to acetate, attributed to the increased CO coverage and local pH. Under optimized conditions, the Faradaic efficiency and partial current density of multicarbon products reach 90.0% and 3.1 A cm-2, corresponding to a carbon selectivity of 100.0% and yield of 75.0%, outperforming thermocatalytic CO hydrogenation. The scale-up demonstration using an electrolyser stack achieves the highest ethylene formation rate of 457.5 ml min-1 at 150 A and acetate formation rate of 2.97 g min-1 at 250 A.

Selective CO2 Electroreduction to Ethanol over a Carbon-Coated CuOx Catalyst.

The design of efficient copper(Cu)-based catalysts is critical for CO2 electroreduction into multiple carbon products. However, most Cu-based catalysts are favorable for ethylene production while selective production of ethanol with high Faradaic efficiency and current density still remains a great challenge. Herein, we design a carbon-coated CuOx (CuOx @C) catalyst through one-pot pyrolysis of Cu-based metal-organic framework (MOF), which exhibits high selectivity for CO2 electroreduction to ethanol with Faradaic efficiency of 46 %. Impressively, the partial current density of ethanol reaches 166 mA cm-2 , which is higher than that of most reported catalysts. Operando Raman spectra indicate that the carbon coating can efficiently stabilize Cu+ species under CO2 electroreduction conditions, which promotes the C-C coupling step. Density functional theory (DFT) calculations reveal that the carbon layer can tune the key intermediate *HOCCH goes the hydrogenation pathway toward ethanol production.

Development of real-time intelligent films from red pitaya peel and its application in monitoring the freshness of pork.

BACKGROUND: Red pitaya peel (RPP) is a good source of polysaccharides, which can be used in the production of biodegradable material. Betacyanins in it possess antioxidant and pH-sensitive properties. However, RPP is commonly discarded during fruit processing. This study aimed to develop real-time intelligent film using RPP to evaluate pork freshness. RESULTS: Real-time intelligent films were developed with film-forming substrates (FFS) composed of 60-100% (w/w) RPP and 0-4% (v/w) glycerol in pH 4.3 ~ 8.0. Rheology tests revealed that the FFS exhibited shear-thinning behavior. Fourier-transform infrared (FTIR) analysis showed that molecules in the RPP interacted with glycerol and formed hydrogen bonds. It showed that the film developed with FFS of 80% RPP and 2% (v/w) glycerol had strong molecular interaction, dense structure, and optimal tensile strength and elongation at break. Film with pH adjusted to 7.0 had greater sensitivity to ammonia than film that was prepared at an original pH of 4.3, so this film was used to monitor freshness of pork. A visible change in the color of the film was observed during the spoiling process of pork, which correlated with the accumulated total volatile base nitrogen. CONCLUSION: Based on its sensitivity to ammonia, the film made of 80% (w/w) RPP and 2% (v/w) glycerol at pH 7.0 was recommended for use in monitoring the freshness of protein-rich food. Our findings are of great significance for ensuring meat quality and safety and for reducing food waste. © 2022 Society of Chemical Industry.