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Freestanding electrodes without the influences of additives have been considered as a kind of ideal electrode structure in the field of capacitive deionization (CDI). However, subjected to conductivity, available surface areas, hydrophilicity and etc., effectively construction of freestanding CDI electrodes with high water desalination performance still face great challenges. Herein, we will demonstrate a unique N-doped graphene freestanding porous membrane electrode with excellent water desalination performance. The preparation process mainly includes the assembly of core-shell composites with incomplete graphene oxide shells into bulk membranes using compression molding method and the heat-treatment under NH3 atmosphere. These reserved spherical shells with loopholes and N-doping make up the freestanding membrane electrodes with network porous architecture. The interconnected sphere shells efficiently improve the availability of surface and pores in the monolithic assembly, while the doping of nitrogen element further enhances the accessibility of graphene-based surface by the electrolyte. As a result, such graphene carbonaceous freestanding electrodes exhibit excellent water desalination performance with a high CDI capacity of about 21.8 mg/g in NaCl solution. Moreover, such freestanding membrane electrodes also possess good desalination abilities towards some other salts such as KCl, CaCl2 and MgCl2, suggesting their potential applications in complex brine solution.

Iodine(i) doped ZnO nanoarray films (ZnO/I-X) were prepared on a silicon wafer by the in itu growth method.

Ultrathin Bi2TiO4F2 with highly dispersed AuPd alloy nanoparticles as cocatalysts enables efficient photocatalytic conversion of methane to methanol with 93.5% selectivity at ambient temperature.

ispartof: ACS SUSTAINABLE CHEMISTRY & ENGINEERING vol:10 issue:1 pages:16-22 status: published

Sunlight is an abundant and clean energy source, the harvesting of which could make a significant contribution to society's increasing energy demands. Metal halide perovskites (MHP) have recently received attention for solar fuel generation through photocatalysis and solar-driven electrocatalysis. However, MHP photocatalysis is limited by low solar energy conversion efficiency, poor stability, and impractical reaction conditions. Compared to photocatalysis, MHP solar-driven electrocatalysis not only exhibits higher solar conversion efficiency but also is more stable when operating under practical reaction conditions. In this Perspective, we outline three leading types of MHP solar-driven electrocatalysis device technologies now in the research spotlight, namely, (1) photovoltaic-electrochemical (PV-EC), (2) photovoltaic-photoelectrochemical (PV-PEC), and (3) photoelectrochemical (PEC) approaches for solar-to-fuel reactions, including water-splitting and the CO2 reduction reaction. In addition, we compare each technology to show their relative technical advantages and limitations and highlight promising research directions for the rapidly emerging scientific field of MHP-based solar-driven electrocatalysis. ispartof: JOURNAL OF PHYSICAL CHEMISTRY LETTERS vol:13 issue:1 pages:25-41 ispartof: location:United States status: published

Crystalline covalent organic frameworks (COFs) are porous polymeric semiconductors with network topologies, which are built from the integration of selected organic blocks with covalent bond linkages. They have shown great promise for artificial photosynthesis, owing to broad light harvesting, high crystallinity, and high carrier mobility. This Minireview introduces state-of-the-art COF photocatalysts based on different linkages and discusses the origin of photocatalytic activities for hydrogen evolution. Three typical COF photocatalysts, with linkages including imine (-C=N-), β-ketoenamine (O=C-C=C-NH-), and vinylene (-C=C-), are discussed with a particular focus on the advancements in synthetic methodologies and structural design, as well as photoelectronic properties that are relevant to photocatalytic performance. The Minireview is expected to elucidate their structure-property relationships and the way to design photoactive COFs with enhanced performances.

Single-atom metal-insulator-semiconductor (SMIS) heterojunctions based on Sn-doped Fe2 O3 nanorods (SF NRs) were designed by combining atomic deposition of an Al2 O3 overlayer with chemical grafting of a RuOx hole-collector for efficient CO2 -to-syngas conversion. The RuOx -Al2 O3 -SF photoanode with a 3.0 nm thick Al2 O3 overlayer gave a >5-fold-enhanced IPCE value of 52.0 % under 370 nm light irradiation at 1.2 V vs. Ag/AgCl, compared to the bare SF NRs. The dielectric field mediated the charge dynamics at the Al2 O3 /SF NRs interface. Accumulation of long-lived holes on the surface of the SF NRs photoabsorber aids fast tunneling transfer of hot holes to single-atom RuOx species, accelerating the O2 -evolving reaction kinetics. The maximal CO-evolution rate of 265.3 mmol g-1 h-1 was achieved by integration of double SIMS-3 photoanodes with a single-atom Ni-doped graphene CO2 -reduction-catalyst cathode; an overall quantum efficiency of 5.7 % was recorded under 450 nm light irradiation.

Plasmon induced hot carrier transfer is a promising novel approach for solar energy conversion, but its practical application is often hindered by its low efficiency. This work demonstrates an unpr...

Photocatalytic overall water splitting is considered as an ideal solution to the energy crisis by converting inexhaustible solar energy into hydrogen energy. However, the practical application of p...

This work demonstrated the rational design and synthesis of donor–π–acceptor (D–π–A) linear vinylene-linked polymers for visible-light driven H2 production with high efficiency. Extending the in-plane conjugation, enhancing the electron push–pull interaction or/and lowering the steric hindrance of the D–π–A type linear conjugated polymer could broaden the visible-light absorption band, promote the photogenerated charge separation and transfer, and thus improve the photocatalytic performance.

The design and synthesis of two semiconducting bis (4-ethynyl-bridging 1, 8-naphthalimide) bolaamphiphiles (BENI-COO- and BENI-NH3 + ) to fabricate supramolecular metal-insulator-semiconductor (MIS) nanostructures for biomimetic hydrogen evolution under visible light irradiation is presented. A H2 evolution rate of ca. 3.12 mmol g-1 ⋅h-1 and an apparent quantum efficiency (AQE) of ca. 1.63 % at 400 nm were achieved over the BENI-COO- -NH3 + -Ni MIS photosystem prepared by electrostatic self-assembly of BENI-COO- with the opposite-charged DuBois-Ni catalysts. The hot electrons of photoexcited BENI-COO- nanofibers were tunneled to the molecular Ni collectors across a salt bridge and an alkyl region of 2.2-2.5 nm length at a rate of 6.10×108 s-1 , which is five times larger than the BENI-NH3 + nanoribbons (1.17×108 s-1 ). The electric field benefited significantly the electron tunneling dynamics and compensated the charge-separated states insufficient in the BENI-COO- nanofibers.

Metal halide perovskites with direct band gap and strong light absorption are promising materials for harvesting solar energy; however, their relatively narrow band gap limits their redox ability when used as a photocatalyst. Adding a second semiconductor component with the appropriate band structure offsets can generate a Z-scheme photocatalytic system, taking full advantage of the perovskite's intrinsic properties. In this work, we develop a direct Z-scheme photocatalyst based on formamidinium lead bromide and bismuth tungstate (FAPbBr3/Bi2WO6) with strong redox ability for artificial solar-to-chemical energy conversion. With desirable band offsets and strong joint redox potential, the dual photocatalyst is shown to form a semicoherent heterointerface. Ultrafast transient infrared absorption studies employing selective excitation reveal synergetic photocarrier dynamics and demonstrate Z-scheme charge transfer mechanisms. Under simulated solar irradiation, a large driving force photoredox reaction (∼2.57 eV) of CO2 reduction coupled with benzyl alcohol oxidation to benzaldehyde is achieved on the Z-scheme FAPbBr3/Bi2WO6 photocatalyst, harnessing the full synergetic potential of the combined system.

We demonstrate a new case of materials-gene engineering to precisely design photocatalysts with the prescribed properties. Based on theoretical calculations, a phase-doping strategy was proposed to regulate the pathways of CO2 conversion over Au nanoparticles (NPs) loaded TiO2 photocatalysts. As a result, the thermodynamic bottleneck of CO2 -to-CO conversion is successfully unlocked by the incorporation of stable twinning crystal planes into face-centered cubic (fcc) phase Au NPs. Compared to bare pristine TiO2 , the activity results showed that the loading of regular fcc-Au NPs raised the CO production by 18-fold but suppressed the selectivity from 84 % to 75 %, whereas Au NPs with twinning (110) and (100) facets boosted the activity by nearly 40-fold and established near unity CO selectivity. This enhancement is shown to originate from a beneficial shift in the surface reactive site energetics arising at the twinned stacking fault, whereby both the CO reaction energy and desorption energy were significantly reduced. ispartof: Angewandte Chemie-International Edition vol:61 issue:28 ispartof: location:Germany status: published

Developing light-harvesting materials with broad spectral response is of fundamental importance in full-spectrum solar energy conversion. We found that, when a series of earth-abundant metal (Cu, Co, Ni and Fe) salts are dissolved in coordinating solvents uniformly dispersed nanodots (NDs) are formed rather than fully dissolving as molecular species. The previously unrecognized formation of this condensed state is ascribed to spontaneous aggregation of molecular transition-metal-complexes (TMCs) via weak intermolecular interactions, which results in redshifted and broadened absorption into the NIR region (200-1100 nm). Typical photoredox reactions, such as carbonylation and oxidative dehydrogenation, well demonstrate the feasibility of efficient utilization of NIR light (λ780 nm) by TMCs NDs. Our finding provides a conceptually new strategy for extending the absorption towards low energy photons in solar energy harvesting and conversion via photoredox transformations.

Fe-BiOCl-Vo nanosheets with electron-capture centers of doped Fe and surface oxygen vacancies (Vo) for enhanced photocatalytic-Fenton performances were conducted. Compared with pristine BiOCl nanosheets, the band gap of the resulting Fe-BiOCl-Vo nanosheets was narrowed, and defective bands were introduced due to the Fe doping and Vo. Furthermore, the integrated electron trapping effect of Vo and doped Fe can efficiently drive charge transfer and separation. As a result, the photocatalytic-Fenton performances of phenol over Fe-BiOCl-Vo nanosheets were enhanced. The photocatalytic-Fenton performances of Fe-BiOCl-Vo nanosheets were enhanced two-fold and four-fold, respectively, as compared with the photocatalytic performances of Fe-BiOCl-Vo and pristine BiOCl nanosheets. During the photocatalytic-Fenton process, the multiple reactive species referring holes (h+), superoxide radicals (●O2−), and hydroxyl radicals (●OH) induced by the efficiently separated charge carriers and Fenton reaction played synergetic roles in phenol degradation and mineralization. This work provides a sophisticated structure design of catalysts for efficient charge transfer and separation, promoting photocatalytic-Fenton performance.

D-π-A type 4-((9-phenylcarbazol-3-yl)ethynyl)-N-dodecyl-1,8-naphthalimide (CZNI) with a large dipole moment of 8.49 D and A-π-A type bis[(4,4'-1,8-naphthalimide)-N-dodecyl]ethyne (NINI) with a negligible dipole moment of 0.28 D, were smartly designed and synthesized to demonstrate the evidence of a molecular dipole as the dominant mechanism for controlling charge separation of organic semiconductors. In aqueous solution, these two novel naphthalimides can self-assemble to form nanoribbons (NRs) that present significantly different traces of exciton dissociation dynamics. Upon photoexcitation of NINI-NRs, no charge-separated excitons (CSEs) are formed due to the large exciton binding energy, accordingly there is no hydrogen evolution. On the contrary, in the photoexcited CZNI-NRs, the initial bound Frenkel excitons are dissociated to long-lived CSEs after undergoing ultrafast charge transfer within ca. 1.25 ps and charge separation within less than 5.0 ps. Finally, these free electrons were injected into Pt co-catalysts for reducing protons to H

The diverse nature of organic precursors offers a versatile platform for precisely tailoring the electronic properties of semiconducting polymers. In this study, three fully conjugated sp2 carbon-linked polymers have been designed and synthesized for photocatalytic hydrogen evolution under visible-light illumination, by copolymerizing different C3 -symmetric aromatic aldehydes as knots with the 1,4-phenylene diacetonitrile (PDAN) linker through a C=C condensation reaction. The hydrogen evolution (HER) is achieved at a maximum rate of 30.2 mmol g-1 h-1 over a polymer based on 2,4,6-triphenyl-1,3,5-triazine units linked by cyano-substituted phenylene, with an apparent quantum yield (AQY) of 7.20 % at 420 nm. Increasing the degree of conjugation and planarity not only extends visible-light absorption, but also stabilizes the fully conjugated sp2 -carbon-linked donor-acceptor (D-A) polymer. Incorporating additional electron-withdrawing triazine units into the D-A polymer to form multiple electron donors and acceptors can greatly promote exciton separation and charge transfer, thus significantly enhancing the photocatalytic activity.

Selective photoreduction of CO2 into a given product is a great challenge but desirable. Inspired by natural photosynthesis occurring in hierarchical networks over non-precious molecular metal catalysts, we demonstrate an integration of single Ni sites into the hexagonal pores of polyimide covalent organic frameworks (PI-COFs) for selective photoreduction of CO2 to CO. The single Ni sites in the hexagonal pores of the COFs serve as active sites for CO2 activation and conversion, while the PI-COFs not only act as a photosensitizer to generate charge carriers but also exert a promoting effect on the selectivity. The optimized PI-COF with a triazine ring exhibits excellent activity and selectivity. A possible intra- and inter-molecular charge-transfer mechanism was proposed, in which the photogenerated electrons in PI-COFs are efficiently separated from the central ring to the diimide linkage, and then transferred to the single Ni active sites, as evidenced by theoretical calculations.

Defect engineering in photocatalysts represents a fundamental method toward tailoring their solar-to-chemical energy conversion performance, although determining the nature and impact of subsurface...

A metal-insulator-semiconductor (MIS) photosystem based on covalent organic framework (COF) semiconductors was designed for robust and efficient hydrogen evolution under visible-light irradiation. A maximal H2 evolution rate of 8.42 mmol h-1 g-1 and a turnover frequency of 789.5 h-1 were achieved by using a MIS photosystem prepared by electrostatic self-assembly of polyvinylpyrrolidone (PVP) insulator-capped Pt nanoparticles (NPs) with the hydrophilic imine-linked TP-COFs having =C=O-H-N= hydrogen-bonding groups. The hot π-electrons in the photoexcited n-type TP-COF semiconductors can be efficiently extracted and tunneled to Pt NPs across an ultrathin PVP insulating layer to reduce protons to H2 . Compared to the Schottky-type counterparts, the COF-based MIS photosystems give a 32-fold-enhanced carrier efficiency, attributed to the combined enhancement of photoexcitation rate, charge separation, and oxidation rate of holes accumulated in the valence band of the TP-COF semiconductor.

Colloidal nanocrystals (NCs) can be generally classified as either excitonic or plasmonic. Excitonic NCs can find applications in photocatalysis and light emitting devices; in contrast, plasmonic N...

The HZSM-5 molecular sieves are a kind of special photocatalyst with photocatalytic activity, while their relationship between structure and function has been a matter of debate. Here, we report that for HZSM-5, the distinguished transformation of coordination environment derived from the removal of tetrahedral framework aluminium by thermal treatment will result in a considerable change in photocatalytic behaviours. The established NMR analysis combined with the theoretical calculations demonstrates the formation of extra-framework aluminium (EFAL) upon calcinations. This leads to a changed reaction path of photocatalytic oxidation of isopropyl alcohol in gas-phase over calcined HZSM-5 catalysts. DFT calculation results show the formed of EFAL species can increase the interaction energy between reactant molecules and zeolites which affords an outstanding photocatalytic reactivity and a controllable photocatalytic selectivity in the oxidation of isopropyl alcohol. This clearly indicates that the framework aluminium (FAL) species are responsible for acetone formation, while the EFAL species are apt to promote the deep mineralization of isopropyl alcohol to inorganic CO2. This study provides new understanding in the issue of photocatalysis for zeolite molecular sieves.

Significance Oxidation and reduction steps in catalysis are always in series, and excellent activity can be achieved when they occur in close proximity. Photooxidation and photoreduction are generally separated and rarely in series. This work develops defect engineering at the metal–oxide interface to make photooxidation sites close to photoreduction sites. Taking solar hydrogen production from aqueous alcohols over Pt/ T i O 2 as an example, the proximity effect triggers unusual reactions and thus increases hydrogen yield per photon from 0.046 to 1.28. Our study provides a direction for the development of efficient photocatalysis.

An artificial photosynthetic (APS) system consisting of a photoanodic semiconductor that harvests solar photons to split H2 O, a Ni-SNG cathodic catalyst for the dark reaction of CO2 reduction in a CO2 -saturated NaHCO3 solution, and a proton-conducting membrane enabled syngas production from CO2 and H2 O with solar-to-syngas energy-conversion efficiency of up to 13.6 %. The syngas CO/H2 ratio was tunable between 1:2 and 5:1. Integration of the APS system with photovoltaic cells led to an impressive overall quantum efficiency of 6.29 % for syngas production. The largest turnover frequency of 529.5 h-1 was recorded with a photoanodic N-TiO2 nanorod array for highly stable CO production. The CO-evolution rate reached a maximum of 154.9 mmol g-1 h-1 in the dark compartment of the APS cell. Scanning electrochemical-atomic force microscopy showed the localization of electrons on the single-nickel-atom sites of the Ni-SNG catalyst, thus confirming that the multielectron reduction of CO2 to CO was kinetically favored.

This work demonstrated the 12 fold-enhanced solar water splitting over the type-II core-shell nanostructured TiO2 rutile photoanodes by orienting the charge flow and accelerating the hole transport to water-oxidation sites. Such nanoheterostructured photoanodes were designed rationally and prepared by a facile strategy to enwrapping an amorphous Ta2OxNy layer on surface of TiO2 nanorods grown on the FTO glass substrates, consequently the incident photon-to-current conversion efficiency was increased from 2.2% to 22.6% in a two-electrode system under 390 nm light irradiation. The activity results showed that under AM 1.5 G illumination, the photocurrent output of TiO2@Ta2OxNy photoanodes reached a stable density of 1.32 mA cm−2 at 1.23 V vs RHE, and which is 12 times and ca. 4.3 times than that of the pristine TiO2 and TiO2@Ta2O5 counterparts, respectively. Correspondingly, the oxygen evolution rate was improved from 20.3 to 112.7 mmol m−2 h−1. A solar-to-chemical energy conversion efficiency of ca. 1.49% was achieved at 1.23 V vs RHE.

TiO2@Ni(OH)2 core-shell microspheres were synthesized by a facile strategy to obtain a perfect 3D flower-like nanostructure with well-arranged Ni(OH)2 nanoflakes on the surfaces of TiO2 microspheres; this arrangement led to a six-fold enhancement in photocatalytic hydrogen evolution. The unique p-n type heterostructure not only promotes the separation and transfer of photogenerated charge carriers significantly, but also offers more active sites for photocatalytic hydrogen production. A photocatalytic mechanism is proposed based on the results of electrochemical measurements and X-ray photoelectron spectroscopy.