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Metal-free carbon-based materials are one of the most promising electrocatalysts toward 2-electron oxygen reduction reaction (2e-ORR) for on-site production of hydrogen peroxide (H2O2), which however suffer from uncontrollable carbonizations and inferior 2e-ORR selectivity. To this end, a polydopamine (PDA)-modified carbon catalyst with a dipole-dipole enhancement is developed via a calcination-free method. The H2O2 yield rate outstandingly reaches 1.8 mol gcat -1 h-1 with high faradaic efficiency of above 95% under a wide potential range of 0.4-0.7 VRHE, overwhelming most of carbon electrocatalysts. Meanwhile, within a lab-made flow cell, the synthesized ORR electrode features an exceptional stability for over 250 h, achieved a pure H2O2 production efficacy of 306 g kWh-1. By virtue of its industrial-level capabilities, the established flow cell manages to perform a rapid pulp bleaching within 30 min. The superior performance and enhanced selectivity of 2e-ORR is experimentally revealed and attributed to the electronic reconfiguration on defective carbon sites induced by non-covalent dipole-dipole influence between PDA and carbon, thereby prohibiting the cleavage of O-O in OOH intermediates. This proposed strategy of dipole-dipole effects is universally applicable over 1D carbon nanotubes and 2D graphene, providing a practical route to design 2e-ORR catalysts.
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The directional conversion of methane to ethylene is challenging due to the dissociation of the CâH bond and the self-coupling of methyl intermediates. Herein, a novel W/WO3- x catalyst with the fork vein structure consisting of an alternating arrangement of WO3- x and W is developed. Impressively, the catalyst achieves an unprecedented C2H4 yield of 1822.73 µmol g-1 h-1, with a selectivity of 82.49%. The enhanced catalytic activity is ascribed to the multifunctional synergistic effect induced by oxygen vacancies and W sites in W/WO3- x. Oxygen vacancies provide abundant coordination of unsaturation sites, which promotes the adsorption and activation of CH4, thus reducing the dissociation energy barrier of the CâH bond. The CH2 coupling barrier on the metal W surface is significantly lower compared to WO3, so CH2 can migrate to the W site for coupling. Importantly, the W/WO3- x with high periodicity provides multiple ordered local microelectric fields, and CH2 intermediates with dipole moments undergo orientation polarization and displacement polarization driven by the electric field, thus enabling CH2 migration. This work opens a new avenue for the structural design and modulation of photocatalysts, and provides new perspectives on the migration of methylene between multiple active sites.
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Perovskite oxides are proven as a striking platform for developing high-performance electrocatalysts. Nonetheless, a significant portion of them show CO2 electroreduction (CO2RR) inertness. Here a simple but effective strategy is reported to activate inert perovskite oxides (e.g., SrTiO3) for CO2RR through slight Cu2+ doping in B-sites. For the proof-of-concept catalysts of SrTi1-xCuxO3 (x = 0.025, 0.05, and 0.1), Cu2+ doping (even in trace amount, e.g., x = 0.025) can not only create active, stable CuO6 octahedra, increase electrochemical active surface area, and accelerate charge transfer, but also significantly regulate the electronic structure (e.g., up-shifted band center) to promote activation/adsorption of reaction intermediates. Benefiting from these merits, the stable SrTi1-xCuxO3 catalysts feature great improvements (at least an order of magnitude) in CO2RR activity and selectivity for high-order products (i.e., CH4 and C2+), compared to the SrTiO3 parent. This work provides a new avenue for the conversion of inert perovskite oxides into high-performance electrocatalysts toward CO2RR.
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Selective photocatalytic CO2 reduction to high-value hydrocarbons using graphitic carbon nitride (g-C3N4) polymer holds great practical significance. Herein, the cyano-functionalized g-C3N4 (CN-g-C3N4) with a high local electron density site is successfully constructed for selective CO2 photoreduction to CH4 and C2H4. Wherein the potent electron-withdrawing cyano group induces a giant internal electric field in CN-g-C3N4, significantly boosting the directional migration of photogenerated electrons and concentrating them nearby. Thereby, a high local electron density site around its cyano group is created. Moreover, this structure can also effectively promote the adsorption and activation of CO2 while firmly anchoring *CO intermediates, facilitating their subsequent hydrogenation and coupling reactions. Consequently, using H2O as a reducing agent, CN-g-C3N4 achieves efficient and selective photocatalytic CO2 reduction to CH4 and C2H4 activity, with maximum rates of 6.64 and 1.35 µmol g-1 h-1, respectively, 69.3 and 53.8 times higher than bulk g-C3N4 and g-C3N4 nanosheets. In short, this work illustrates the importance of constructing a reduction site with high local electron density for efficient and selective CO2 photoreduction to hydrocarbons.
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Despite the intriguing potential, nano-socketed Cu/perovskite heterostructures for CO2 electroreduction (CO2RR) are still in their infancy and rational optimization of their CO2RR properties is lacking. Here, an effective strategy is reported to promote CO2-to-C2+ conversion over nano-socketed Cu/perovskite heterostructures by A-site-valence-controlled oxygen vacancies. For the proof-of-concept catalysts of Cu/La0.3-xSr0.6+xTiO3-δ (x from 0 to 0.3), their oxygen vacancy concentrations increase controllably with the decreased A-site valences (or the increased x values). In flow cells, their activity and selectivity for C2+ present positive correlations with the oxygen vacancy concentrations. Among them, the Cu/Sr0.9TiO3-δ with most oxygen vacancies shows the optimal activity and selectivity for C2+. And relative to the Cu/La0.3Sr0.6TiO3-δ with minimum oxygen vacancies, the Cu/Sr0.9TiO3-δ exhibits marked improvements (up to 2.4 folds) in activity and selectivity for C2+. The experiments and theoretical calculations suggest that the optimized performance can be attributed to the merits provided by oxygen vacancies, including the accelerated charge transfer, enhanced adsorption/activation of reaction species, and reduced energy barrier for CâC coupling. Moreover, when explored in a membrane-electrode assembly electrolyzer, the Cu/Sr0.9TiO3-δ catalyst shows excellent activity, selectivity (43.9%), and stability for C2H4 at industrial current densities, being the most effective perovskite-based catalyst for CO2-to-C2H4 conversion.
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Organic supramolecular photocatalysts have garnered widespread attention due to their adjustable structure and exceptional photocatalytic activity. Herein, a novel bis-dicarboxyphenyl-substituent naphthalenediimide self-assembly supramolecular photocatalyst (SA-NDI-BCOOH) with efficient dual-functional photocatalytic performance is successfully constructed. The large molecular dipole moment and short-range ordered stacking structure of SA-NDI-BCOOH synergistically create a giant internal electric field (IEF), resulting in a remarkable 6.7-fold increase in its charge separation efficiency. Additionally, the tetracarboxylic structure of SA-NDI-BCOOH greatly enhances its hydrophilicity. Thus, SA-NDI-BCOOH demonstrates efficient dual-functional activity for photocatalytic hydrogen and oxygen evolution, with rates of 372.8 and 3.8 µmol h-1, respectively. Meanwhile, a notable apparent quantum efficiency of 10.86% at 400 nm for hydrogen evolution is achieved, prominently surpassing many reported supramolecular photocatalysts. More importantly, with the help of dual co-catalysts, it exhibits photocatalytic overall water splitting activity with H2 and O2 evolution rates of 3.2 and 1.6 µmol h-1. Briefly, this work sheds light on enhancing the IEF by controlling the molecular polarity and stacking structure to dramatically improve the photocatalytic performance of supramolecular materials.
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Optimizing the interatomic distance of dual sites to realize C-C bond breaking of ethanol is critical for the commercialization of direct ethanol fuel cells. Herein, the concept of holding long-range dual sites is proposed to weaken the reaction barrier of C-C cleavage during the ethanol oxidation reaction (EOR). The obtained long-range Rh-O-Pt dual sites achieve a high current density of 7.43 mA/cm2 toward EOR, which is 13.3 times that of Pt/C, as well as remarkable stability. Electrochemical in situ Fourier transform infrared spectroscopy indicates that long-range Rh-O-Pt dual sites can increase the selectivity of C1 products and suppress the generation of a CO intermediate. Theoretical calculations further disclose that redistribution of the surface-localized electron around Rh-O-Pt can promote direct oxidation of -OH, accelerating C-C bond cleavage. This work provides a promising strategy for designing oxygen-bridged long-range dual sites to tune the activity and selectivity of complicated catalytic reactions.
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The co-assembly naphthalimide/perylene diimide (NDINH/PDINH) supramolecular photocatalysts were successfully synthesized via a rapid solution dispersion method. A giant internal electric field (IEF) in co-assembly structure was built by the larger local dipole. NDINH coated on PDINH could reduce the reflected electric field over PDINH to improve its responsive activity to ultraviolet light. Resultantly, an efficient full-spectrum photocatalytic overall water splitting activity with H2 and O2 evolution rate of 317.2 and 154.8â µmol g-1 h-1 for NDINH/PDINH together with optimized O2 evolution rate with 2.61â mmol g-1 h-1 using AgNO3 as a sacrificial reagent were achieved. Meanwhile, its solar-to-hydrogen efficiency was enhanced to 0.13 %. The enhanced photocatalytic activity was primarily attributed to the IEF between NDINH and PDINH, significantly accelerating transfer and separation of photogenerated carriers. Additionally, a direct Z-Scheme pathway of carriers contributed to a high redox potential. The strategy provided a new perspective for the design of supramolecular photocatalysts.
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Nature-inspired supramolecular self-assemblies are attractive photocatalysts, but their quantum yields are limited by poor charge separation and transportation. A promising strategy for efficient charge transfer is to enhance the built-in electric field by symmetry breaking. Herein, an unsymmetric protonation, N-heterocyclic π-conjugated anthrazoline-based supramolecular photocatalyst SA-DADK-H+ was developed. The unsymmetric protonation breaks the initial structural symmetry of DADK, resulting in ca. 50-fold increase in the molecular dipole, and facilitates efficient charge separation and transfer within SA-DADK-H+. The protonation process also creates numerous active sites for H2O adsorption, and serves as crucial proton relays, significantly improving the photocatalytic efficiency. Remarkably, SA-DADK-H+ exhibits an outstanding hydrogen evolution rate of 278.2â mmol g-1 h-1 and a remarkable apparent quantum efficiency of 25.1 % at 450â nm, placing it among the state-of-the-art performances in organic semiconductor photocatalysts. Furthermore, the versatility of the unsymmetric protonation approach has been successfully applied to four other photocatalysts, enhancing their photocatalytic performance by 39 to 533â times. These findings highlight the considerable potential of unsymmetric protonation induced symmetry breaking strategy in tailoring supramolecular photocatalysts for efficient solar-to-fuel production.
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Heterocycle-linked phthalocyanine-based COFs with close-packed π-π conjugated structures are a kind of material with intrinsic electrical conductivity, and they are considered to be candidates for photoelectrical devices. Previous studies have revealed their applications for energy storage, gas sensors, and field-effect transistors. However, their potential application in photodetector is still not fully studied. The main difficulty is preparing high-quality films. In our study, we found that our newly designed benzimidazole-linked Cu (II)-phthalocyanine-based COFs (BICuPc-COFs) film can hardly formed with a regular aerobic oxidation method. Therefore, we developed a transfer dehydrogenation method with N-benzylideneaniline (BA) as a mild reagent. With this in hand, we successfully prepared a family of high crystalline BICuPc-COFs powders and films. Furthermore, both of these new BICuPc-COFs films showed high electrical conductivity (0.022-0.218â S/m), higher than most of the reported COFs materials. Due to the broad absorption and high conductivity of BICuPc-COFs, synaptic devices with small source-drain voltage (VDS=1â V) were fabricated with response light from visible to near-infrared. Based on these findings, we expect this study will provide a new perspective for the application of conducting heterocycle-linked COFs in synaptic devices.
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Electrocatalytic reduction of CO2 into C2 products of high economic value provides a promising strategy to realize resourceful CO2 utilization. Rational design and construct dual sites to realize the CO protonation and C-C coupling to unravel their structure-performance correlation is of great significance in catalysing electrochemical CO2 reduction reactions. Herein, Cu-Cu dual sites with different site distance coordinated by halogen at the first-shell are constructed and shows a higher intramolecular electron redispersion and coordination symmetry configurations. The long-range Cu-Cu (Cu-I-Cu) dual sites show an enhanced Faraday efficiency of C2 products, up to 74.1%, and excellent stability. In addition, the linear relationships that the long-range Cu-Cu dual site is accelerated to C2H4 generation and short-range Cu-Cu (Cu-Cl-Cu) dual site is beneficial for C2H5OH formation are disclosed. In situ electrochemical attenuated total reflection surface enhanced infrared absorption spectroscopy, in situ Raman and theoretical calculations manifest that long-range Cu-Cu dual sites can weaken reaction energy barriers of CO hydrogenation and C-C coupling, as well as accelerating deoxygenation of *CH2CHO. This study uncovers the exploitation of site-distance-dependent electrochemical property to steer the CO2 reduction pathway, as well as a potential generic tactic to target C2 synthesis by constructing the desired Cu-Cu dual sites.
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The Fenton process is a widely used to remedy organic wastewaters, but it has problems of adding H2O2, low utilization efficiency of H2O2 and low mineralization efficiency. Here, a new photocatalysis-self-Fenton process was exploited for the removal of persistent 4-chlorophenol (4-CP) pollutant through coupling the photocatalysis of 4-carboxyphenylboronic acid edge covalently modified g-C3N4 (CPBA-CN) with Fenton. In this process, H2O2 was in situ generated via photocatalysis over CPBA-CN, the photogenerated electrons assisted the accelerated regeneration of Fe2+ to improve the utilization efficiency of H2O2, and the photogenerated holes facilitated the enhancement of 4-CP mineralization. Under the conjugation of CPBA, the electronic structure of CN was optimized and the molecular dipole was enhanced, resulting in the deepening valence band position, accelerated electron-hole pair separation, and improved O2 adsorption-activation. Therefore, the incremental 4-CP degradation rate in the CPBA-CN photocatalysis-self-Fenton process was approaching 0.099 min-1, by a factor of 3.1 times compared with photocatalysis. The parallel mineralization efficiency increased to 74.6% that was 2.1 and 2.6 times than photocatalysis and Fenton, respectively. In addition, this system maintained an excellent stability in the recycle experiment and can be potentially applied in a wide range of pHs and under the coexistence of various ions. This study would provide new insights for improving Fenton process and promote further development of Fenton in organic wastewater purification.
Assuntos
Poluentes Ambientais , Poluentes Orgânicos Persistentes , Peróxido de Hidrogênio/química , Oxirredução , Águas Residuárias , CatáliseRESUMO
High-efficiency photocatalysts based on metal-organic frameworks (MOFs) are often limited by poor charge separation and slow charge-transfer kinetics. Herein, a novel MOF photocatalyst is successfully constructed by encapsulating C60 into a nano-sized zirconium-based MOF, NU-901. By virtue of host-guest interactions and uneven charge distribution, a substantial electrostatic potential difference is set-up in C60 @NU-901. The direct consequence is a robust built-in electric field, which tends to be 10.7â times higher in C60 @NU-901 than that found in NU-901. In the catalyst, photogenerated charge carriers are efficiently separated and transported to the surface. For example, photocatalytic hydrogen evolution reaches 22.3â mmol g-1 h-1 for C60 @NU-901, which is among the highest values for MOFs. Our concept of enhancing charge separation by harnessing host-guest interactions constitutes a promising strategy to design photocatalysts for efficient solar-to-chemical energy conversion.
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Development of highly efficient and metal-free photocatalysts for bacterial inactivation under natural light is a major challenge in photocatalytic antibiosis. Herein, we developed an acidizing solvent-thermal approach for inserting a non-conjugated ethylenediamine segment into the conjugated planes of 3,4,9,10-perylene tetracarboxylic anhydride to generate a photocatalyst containing segregated π-conjugation units (EDA-PTCDA). Under natural light, EDA-PTCDA achieved 99.9 % inactivation of Escherichia coli and Staphylococcus aureus (60 and 45â min), which is the highest efficiency among all the natural light antibacterial reports. The difference in the surface potential and excited charge density corroborated the possibility of a built-in electron-trap effect of the non-conjugated segments of EDA-PTCDA, thus forming a highly active EDA-PTDA/bacteria interface. In addition, EDA-PTCDA exhibited negligible toxicity and damage to normal tissue cells. This catalyst provides a new opportunity for photocatalytic antibiosis under natural light conditions.
Assuntos
Elétrons , Luz , Staphylococcus aureus , CatáliseRESUMO
Despite the intriguing potential shown by Sn-based perovskite oxides in CO2 electroreduction (CO2 RR), the rational optimization of their CO2 RR properties is still lacking. Here we report an effective strategy to promote CO2 -to-HCOOH conversion of Sn-based perovskite oxides by A-site-radius-controlled Sn-O bond lengths. For the proof-of-concept examples of Ba1-x Srx SnO3 , as the A-site cation average radii decrease from 1.61 to 1.44â Å, their Sn-O bonds are precisely shortened from 2.06 to 2.02â Å. Our CO2 RR measurements show that the activity and selectivity of these samples for HCOOH production exhibit volcano-type trends with the Sn-O bond lengths. Among these samples, the Ba0.5 Sr0.5 SnO3 features the optimal activity (753.6â mA â cm-2 ) and selectivity (90.9 %) for HCOOH, better than those of the reported Sn-based oxides. Such optimized CO2 RR properties could be attributed to favorable merits conferred by the precisely controlled Sn-O bond lengths, e.g., the regulated band center, modulated adsorption/activation of intermediates, and reduced energy barrier for *OCHO formation. This work brings a new avenue for rational design of advanced Sn-based perovskite oxides toward CO2 RR.
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The development of conjugated polymers especially n-type polymer semiconductors is powered by the design and synthesis of electron-deficient building blocks. Herein, a strong acceptor building block with di-metallaaromatic structure was designed and synthesized by connecting two electron-deficient metallaaromatic units through a π-conjugated bridge. Then, a double-monomer polymerization methodology was developed for inserting it into conjugated polymer scaffolds to yield metallopolymers. The isolated well-defined model oligomers indicated polymer structures. Kinetic studies based on nuclear magnetic resonance and ultraviolet-visible spectroscopies shed light on the polymerization process. Interestingly, the resulted metallopolymers with dπ -pπ conjugations are very promising electron transport layer materials which can boost photovoltaic performance of an organic solar cell, with power conversion efficiency up to 18.28 % based on the PM6 : EH-HD-4F non-fullerene system. This work not only provides a facile route to construct metallaaromatic conjugated polymers with various functional groups, but also discovers their potential applications for the first time.
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Carrier transport is an equally decisive factor as carrier separation for elevating photocatalytic efficiency. However, limited by indefinite structures and low crystallinities, studies on enhancing carrier transport of organic photocatalysts are still in their infancy. Here, we develop an σ-linkage length modulation strategy to enhance carrier transport in imidazole-alkyl-perylene diimide (IMZ-alkyl-PDI, corresponding to D-σ-A) photocatalysts by controlling π-π stacking distance. Ethyl-linkage can shorten π-π stacking distance (3.19â Å) the most among IMZ-alkyl-PDIs (where alkyl=none, ethyl, and n-propyl) via minimizing steric hindrance between D and A moieties, which leads to the fastest carrier transport rates. Thereby, IMZ-ethyl-PDI exhibits remarkable enhancement in phenol degradation with 32-fold higher rates than IMZ-PDI, as well as the oxygen evolution rate (271-fold increased). In microchannel reactors, IMZ-ethyl-PDI also presents 81.5 % phenol removal with high-flux surface hydraulic loading (44.73â L m-2 h-1 ). Our findings provide a promising molecular design guideline for high-performance photocatalysts and elucidate crucial internal carrier transport mechanisms.
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Gas-phase ion-molecule reactions have attracted considerable attention due to their importance in the fields of interstellar chemistry, plasma chemistry, and combustion chemistry. The reaction of an amino radical cation with a hydrogen molecule is one of the crucial steps in the gas-phase formation of ammonia in the interstellar medium (ISM). The dynamics and kinetics of the NH2+ + H2 reaction are studied using the quasi-classical trajectory approach on a newly constructed ab initio potential energy surface (PES) for the ground electronic state. The PES is fitted by the fundamental invariant-neural network method, resulting in a total root mean square error (RMSE) of 0.061 kcal mol-1. Dynamics calculations show that, on one hand, the vibrational excitation of H2 largely promotes the reaction. On the other hand, the fundamental excitation of each vibrational mode of NH2+ inhibits the reaction at low collision energies which has a negligible effect at high collision energies except for the symmetric stretching mode. The relatively higher efficacy of the symmetric stretching mode than that of the asymmetric stretching mode can be rationalized by the underlying reaction mechanisms. In addition, the calculated rate coefficients of the reaction agree reasonably well with the available experimental results.
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The insufficient charge separation and sluggish exciton transport severely limit the utilization of polymeric photocatalysts. To resolve the above issues, we incorporate bountiful carboxyl substituents within a novel benzodiimidazole oligomer and assemble it into a crystalline semiconductor. The photocatalyst is polar, hydrophilic, short-range crystalline, and capable of both hydrogen and oxygen evolution. The introduction of carboxyl side-groups adds asymmetry to the local structure and increases the built-in electric field. Further, accelerated carrier transfer is enabled via the short-range crystallinity. The superior hydrogen and oxygen production rates of 18.63 and 2.87â mmol g-1 h-1 represent one of the best performances ever reported among dual-functional polymeric photocatalysts. Our work initiates studies on high-performance oligomer photocatalysts, opening a new frontier to produce solar fuel.
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We report an effective strategy to enhance CO2 electroreduction (CER) properties of Cu-based Ruddlesden-Popper (RP) perovskite oxides by engineering their A-site cation deficiencies. With La2-x CuO4-δ (L2-x C, x=0, 0.1, 0.2, and 0.3) as proof-of-concept catalysts, we demonstrate that their CER activity and selectivity (to C2+ or CH4 ) show either a volcano-type or an inverted volcano-type dependence on the x values, with the extreme point at x=0.1. Among them, at -1.4â V, the L1.9 C delivers the optimal activity (51.3â mA cm-2 ) and selectivity (41.5 %) for C2+ , comparable to or better than those of most reported Cu-based oxides, while the L1.7 C exhibits the best activity (25.1â mA cm-2 ) and selectivity (22.1 %) for CH4 . Such optimized CER properties could be ascribed to the favorable merits brought by the cation-deficiency-induced oxygen vacancies and/or CuO/RP hybrids, including the facilitated adsorption/activation of key reaction species and thus the manipulated reaction pathways.