Search

Developing efficient photoreversible color switching systems for constructing rewritable paper is of significant practical interest owing to the potential environmental benefits including forest conservation, pollution reduction, and resource sustainability. Here we report that the color change associated with the redox chemistry of nanoparticles of Prussian blue and its analogues could be integrated with the photocatalytic activity of TiO2 nanoparticles to construct a class of new photoreversible color switching systems, which can be conveniently utilized for fabricating ink-free, light printable rewritable paper with various working colors. The current system also addresses the phase separation issue of the previous organic dye-based color switching system so that it can be conveniently applied to the surface of conventional paper to produce an ink-free light printable rewritable paper that has the same feel and appearance as the conventional paper. With its additional advantages such as excellent scalability and outstanding rewriting performance (reversibility >80 times, legible time >5 days, and resolution >5 μm), this novel system can serve as an eco-friendly alternative to regular paper in meeting the increasing global needs for environment protection and resource sustainability.

Electrochemical carbon dioxide reduction (eCO2R) in neutral electrolytes represents a viable solution for alleviating energy and carbon losses associated with carbonate formation, but limited by suboptimal C2+ selectivity and productivity owing to the higher C−C coupling kinetic barrier in such media. To address the issue, here Cu2O nanocubes are encapsulated within metalloporphyrin frameworks to create a benign microenvironment for C−C coupling, with the best catalyst of Cu2O@Cu−TCPP(Co) demonstrating a maximal C2H4 and C2+ FE of 54 ± 2% and 69 ± 4%, respectively, at 500 mA cm−2 in 1 M KCl. Comprehensive structural and spectrometric characterizations utilizing in situ attenuated total reflectance surface‐enhanced infrared absorption spectroscopy (ATR−SEIRAS), in situ X‐ray absorption spectroscopy (XAS), operando Raman, and high‐resolution transmission electron microscopy (HR−TEM) unveil that the high CO2 adsorption endowed by the metal‐organic framework (MOF) overlayer, high CO concentration yield by metalloporphyrins, high local pH rendered by spatial confinement, as well as the highly dispersed Cu crystallites exposing (200) facets synergistically contribute to the asymmetric C−C coupling of *CO and *COH intermediates in favor of C2+ production. Orchestrating the active moieties in a concerted fashion, this study offers a paradigm for the design of eCO2R catalysts in neutral electrolytes. [ABSTRACT FROM AUTHOR]

Breaking the D4h symmetry in the square‐planar M−N4 configuration of macrocycle molecular catalysts has witnessed enhanced electrocatalytic activity, but at the expense of electrochemical stability. Herein, we hypothesize that the lability of the active Cu−N3 motifs in the N‐confused copper (II) tetraphenylporphyrin (CuNCP) could be overcome by applying pulsed potential electrolysis (PPE) during electrocatalytic carbon dioxide reduction. We find that applying PPE can indeed enhance the CH4 selectivity on CuNCP by 3 folds to reach the partial current density of 170 mA cm−2 at >60 % Faradaic efficiency (FE) in flow cell. However, combined ex situ X‐ray diffraction (XRD), transmission electron microscope (TEM), and in situ X‐ray absorption spectroscopy (XAS), infrared (IR), Raman, scanning electrochemical microscopy (SECM) characterizations reveal that, in a prolonged time scale, the decomplexation of CuNCP is unavoidable, and the promoted water dissociation under high anodic bias with lowered pH and enriched protons facilitates successive hydrogenation of *CO on the irreversibly reduced Cu nanoparticles, leading to the improved CH4 selectivity. As a key note, this study signifies the adaption of electrolytic protocol to the catalyst structure for tailoring local chemical environment towards efficient CO2 reduction. [ABSTRACT FROM AUTHOR]

Hybrid organic/inorganic composites with the organic phase tailored to modulate local chemical environment at the Cu surface arise as an enchanting category of catalysts for electrocatalytic CO2 reduction reaction (CO2RR). A fundamental understanding on how the organics of different functionality, polarity, and hydrophobicity affect the reaction path is, however, still lacking to guide rational catalyst design. Herein, polypyrrole (PPy) and polyaniline (PANI) manifesting different Brønsted basicity are compared for their regulatory roles on the CO2RR pathways regarding *CO coverage, proton source and interfacial polarity. Concerted efforts from in situ IR, Raman and operando modelling unveil that at the PPy/Cu interface with limited *CO coverage, hydridic *H produced by the Volmer step favors the carbon hydrogenation of *CO to form *CHO through a Tafel process; Whereas at the PANI/Cu interface with concentrated CO2 and high *CO coverage, protonic H+ shuttled through the benzenoid ‐NH‐ protonates the oxygen of *CO, yielding *COH for asymmetric coupling with nearby *CO to form *OCCOH under favored energetics. As a result of the tailored chemical environment, the restructured PANI/Cu composite demonstrates a high partial current density of 0.41 A cm−2 at a maximal Faraday efficiency of 67.5 % for ethylene production, ranking among states of the art. [ABSTRACT FROM AUTHOR]

Hybrid organic/inorganic composites with the organic phase tailored to modulate local chemical environment at the Cu surface arise as an enchanting category of catalysts for electrocatalytic CO2 reduction reaction (CO2RR). A fundamental understanding on how the organics of different functionality, polarity, and hydrophobicity affect the reaction path is, however, still lacking to guide rational catalyst design. Herein, polypyrrole (PPy) and polyaniline (PANI) manifesting different Brønsted basicity are compared for their regulatory roles on the CO2RR pathways regarding *CO coverage, proton source and interfacial polarity. Concerted efforts from in situ IR, Raman and operando modelling unveil that at the PPy/Cu interface with limited *CO coverage, hydridic *H produced by the Volmer step favors the carbon hydrogenation of *CO to form *CHO through a Tafel process; Whereas at the PANI/Cu interface with concentrated CO2 and high *CO coverage, protonic H+ shuttled through the benzenoid ‐NH‐ protonates the oxygen of *CO, yielding *COH for asymmetric coupling with nearby *CO to form *OCCOH under favored energetics. As a result of the tailored chemical environment, the restructured PANI/Cu composite demonstrates a high partial current density of 0.41 A cm−2 at a maximal Faraday efficiency of 67.5 % for ethylene production, ranking among states of the art. [ABSTRACT FROM AUTHOR]

Cobalt phthalocyanine (CoPc) anchored on heterogeneous scaffold has drawn great attention as promising electrocatalyst for carbon dioxide reduction reaction (CO2RR), but the molecule/substrate interaction is still pending for clarification and optimization to maximize the reaction kinetics. Herein, a CO2RR catalyst is fabricated by affixing CoPc onto the Mg(OH)2 substrate primed with conductive carbon, demonstrating an ultra‐low overpotential of 0.31 ± 0.03 V at 100 mA cm−2 and high faradaic efficiency of >95% at a wide current density range for CO production, as well as a heavy‐duty operation at 100 mA cm−2 for more than 50 h in a membrane electrode assembly. Mechanistic investigations employing in situ Raman and attenuated total reflection surface‐enhanced infrared absorption spectroscopy unravel that Mg(OH)2 plays a pivotal role to enhance the CO2RR kinetics by facilitating the first‐step electron transfer to form anionic *CO2− intermediates. DFT calculations further elucidate that introducing Lewis acid sites help to polarize CO2 molecules absorbed at the metal centers of CoPc and consequently lower the activation barrier. This work signifies the tailoring of catalyst‐support interface at molecular level for enhancing the turnover rate of CO2RR. [ABSTRACT FROM AUTHOR]

Electroreduction of carbon dioxide into value-added fuels or chemicals using renewable energy helps to effectively reduce carbon dioxide emission and alleviate the greenhouse effect while storing intermittent energies. Due to the existing infrastructure of global natural gas utilization and distribution, methane produced in such a green route attracts wide interests. However, limited success has been witnessed in the practical application of catalysts imparting satisfactory methane activity and selectivity. Herein, we report the fabrication of an atomically dispersed Co−Cu alloy through the reconstruction of trace-Co doped Cu metal-organic framework. This catalyst exhibits a methane Faradaic efficiency of 60% ± 1% with the corresponding partial current density of 303 ± 5 mA·cm−2. Operando X-ray adsorption spectroscopy and attenuated-total-reflection surface enhanced infrared spectroscopy unravel that the introduction of atomically dispersed Co in Cu favors *CO protonation via enhancing surface water activation, and suppresses C−C coupling by reducing *CO coverage, thereby leading to high methane selectivity. [ABSTRACT FROM AUTHOR]

Metal nanoparticles have drawn great attention in heterogeneous catalysis. One challenge is that they are easily deactivated by migration-coalescence during the catalysis process because of their high surface energy. With the rapid development of nanoscience, encapsulating metal nanoparticles in nanoshells or nanopores becomes one of the most promising strategies to overcome the stability issue of the metal nanoparticles. Besides, the activity and selectivity could be simultaneously enhanced by taking advantage of the synergy between the metal nanoparticles and the encapsulating materials as well as the molecular sieving property of the encapsulating materials. In this review, we provide a comprehensive summary of the recent progress in the synthesis and catalytic properties of the encapsulated metal nanoparticles. This review begins with an introduction to the synthetic strategies for encapsulating metal nanoparticles with different architectures developed to date, including their encapsulation in nanoshells of inorganic oxides and carbon, porous materials (zeolites, metal–organic frameworks, and covalent organic frameworks), and organic capsules (dendrimers and organic cages). The advantages of the encapsulated metal nanoparticles are then discussed, such as enhanced stability and recyclability, improved selectivity, strong metal–support interactions, and the capability of enabling tandem catalysis, followed by the introduction of some representative applications of the encapsulated metal nanoparticles in thermo-, photo-, and electrocatalysis. At the end of this review, we discuss the remaining challenges associated with the encapsulated metal nanoparticles and provide our perspectives on the future development of the field. [ABSTRACT FROM AUTHOR]