查看更多>>摘要：Electro cat alytic nitrate reduction reaction (NO3RR) is a facile and competitive way to remove NO3~--N, but it still faces challenges of cost and reactivity. Herein, we synthesize a single-atom iron electrode (Fe_(SAs)/B-C3N4) by a facile one-step pyrolysis method and demonstrate a strategy for N=O bond activation with isolated Fe-N4 as the active centre for efficient NO3RR. The catalyst achieved the NO3~--N removal capacity of 9857.5 mg N/g Fe, which was the highest among previous studies, and a high faradaic efficiency of 77.3%, even at a low nitrate concentration (50 mg N/L). The designed pathway combined with electrochlorination can completely convert by-products to harmless nitrogen gas. Theoretical research confirmed the contribution of coexisting hydrogen evolution reaction suppression and NO3RR boosted by N=O activation on Fe-N4. This work offers a new paradigm for designing the efficient, stable, and energy conservation single-atom cathode for development of NO3~--N removal from water bodies.
查看更多>>摘要：Electronic structure and surface character are two important factors of materials for photocatalytic CO2 reduction. Herein, the simultaneous regulation of electronic structure and surface basicity of pyrovanadate A2V2O7 (A = Co, Ni, Cu, Zn) were realized by changing the A-site element. The density functional theory (DFT) results suggested that Ni2V2O7 had the strongest crystal field and the greatest splitting of V 3d, resulting in the largest mobility of photogenerated electrons. Moreover, the Tanabe hypothesis predicted that the A-site cation was a basic surface site, and the CO2-TPD results revealed that Ni~(2+) had the strongest surface basicity. Ni2V2O7 exhibited much higher CO yield of 33.1 μmol/g, compared to Co2V2O7 (16.7 μmol/g) and Zn2V2O7 (12.9 μmol/g). Cu2V2O7 was not suitable for CO2 reduction due to its positive conduction band position caused by splitting the Cu 3d orbital. Altogether, this study could contribute to deeply understanding metal vanadates for photocatalytic CO2 reduction.
查看更多>>摘要：Small-scale on-site artificial photosynthesis of H2O2 from O2 and H2O is an ideal sustainable route. In particularly, g-C3N4 is a very popular catalyst, nevertheless, its photo catalytic activity is severely inhibited by the random migration and rapid recombination of photogenerated carriers. Herein, a well-ordered highly-crystalline g-C3N4 nanoarray with conjugated electron donor-acceptor structure (denoted as PDI/CNA) is rationally designed for efficient H2O2 production to imitate the photosynthesis of natural plants. Both experimental and DFT investigations demonstrate that the tailored PDI/CNA effectively improve charges utilization via eliminating deep defect trapping sites, and reduce its Gibbs free energy (△G) of rate-determining step (*HOOH→H2O2). As a result, the optimized PDI/CNA exhibits a superior H2O2 production rate of 1605.32 μmol g~(-1) h~(-1) and a high apparent quantum yield of 27.18% (λ = 400 nm). This work sheds light on promoting H2O2 photosynthesis by regulating the crystalline structure of g-C3N4 and rationally designing spatially separated redox centers.
查看更多>>摘要：The incorporation of metallic sites into polymer photocatalysts has been a successful strategy to realize high photocatalytic activities. Herein, a series of bimetallic porphyrin-based D-A conjugated polymers M1TAPP-M2Bpy (M1, M2 =H2, Zn, Cu) were prepared through dual metallic sites regulation for enhanced photocatalytic degradation of bisphenol A (BPA) and benzene series pollutants. The π-conjugated polymer skeleton facilitates the adsorption of aromatic pollutants. Superior to monometallic sites, the intrinsic charge transfer characteristics of both porphyrin and bipyridine moieties can be modulated by dual metallic sites, promoting the dissociation of charge carriers. The highly-dispersed metallic reactive sites further boost the photocatalytic activities. Owing to optimized dissociation of electron-hole pairs, CuTAPP-CuBpy exhibits an outstanding photocatalytic oxidation activity for degradation of 50 ppm BPA completely in only 20 min with a relatively fast rate constant of k = 0.183 min~(-1). Dual metallic sites regulation highlighted in this work paves a way toward efficient polymer-based photocatalyst.
查看更多>>摘要：Fe2O3, as an earth-abundant photo catalyst for water purification, has attracted great attention. However, the high-spin Fe~(III) in traditional Fe2O3 restricts its catalytic performance. In this work, based on the nanocrystal size alteration strategy, cubic Fe2O3 nanoclusters (3-4 nm) with low-spin Fe~(III) were successfully anchored on sixfold cavities of the supramolecular condensed g-C3N4 rod (FCN) through the impregnation-coprecipitation method. FCN showed high photo catalytic activity, as the d band center of Fe 3d orbital (-1.79 eV) in low-spin Fe~(III) shifted closer to Femi level, generating a weaker antibonding state. Then, the enhanced bonding state strengthened the interaction between Fe and O, further accelerating the charge carrier separation and enhancing its ability to capture OH~-. Thus, low-spin Fe~(III) enhanced the production of dominant reactive oxygen species (·OH/·O2~-), promoting diclofenac photocatalytic degradation under solar light, with a kinetic rate constant (0.206 min~(-1)) of ～5 times compared with that of pristine g-C3N4.
查看更多>>摘要：Reducing the energy consumption and increasing the additional value of water electrolysis to produce H2 is currently a hot research topic. In this work, we introduce two kinds of promising water electrolysis modes in a diaphragm electrolytic cell for H2 production. When considering the energy consumption, a urea-assisted amphoteric water splitting system was built. This system just needs an ultralow voltage of 0.88 V to attain the current density of 10 mA cm~(-2) with high durability, which leads to a large decrease of energy consumption of 48.55% compared to alkaline water splitting system by the introduction of electrochemical neutralization energy and thermodynamically-favorable urea oxidation reaction. When considering the additional value, a H2-acid-base co-electrosynthesis system was proposed inspired by the chlor-alkali and electrochemical seawater desalination processes. In this system, only K2SO4 electrolytes are needed, and acid-base chemicals and H2 could be generated at a voltage of 2.32 V (10 mA cm~(-2)).
查看更多>>摘要：Photocatalytic CO2 reduction (PCC) into solar fuels has been identified as a green avenue for carbon emission reduction. The reactions are usually restricted by the competitive hydrogen production reactions so that the acquisition and utilization of activated hydrogen (H*) in photocatalytic CO2 reduction are hard to guarantee. Herein, heterojunction engineering, regarding amendatory H* supply and balancing hydrogen production reactions simultaneously, for enhancing PCC is achieved by fabricating black phosphorus (BP) nanosheets supported on Bi_(19)Br3S_(27) nanorods (BP/BBS). Density functional theory calculations united with experimental researches confirm the charge transfer conforms to S-scheme mechanism, which guarantee the efficient separation of photogenerated carriers to facilitate CO2 photoreduction. Free energy analysis reveals the formation of BP/BBS heterojunction changes the active sites from BBS to BP, which decrease the rate-limiting H* formation step from 1.94 (on BBS) to 1.13 eV (BP/BBS heterojunction), ensuring the supply of activated H* for PCC. We found that the heat of the PCC is conducive to dominant protonation of CO2 not H* desorption, which can greatly improve the reduction efficiency of CO2. As a result, the optimized BP/BBS heterojunction achieves an enhanced generation rate of solar fuels in liquid or gas-solid phase system with CO generation rate of 395.7 and 35.4 μmol g~(-1)_(catalyst), respectively. This work provides an efficient strategy to achieve the supply of activated H* for PCC and other photochemical process.
查看更多>>摘要：Electrocatalytic hydrogen evolution reaction (HER) is crucial to clean fuel production. Two-dimensional (2D) transition metal carbides (TMCs) are promising HER electrocatalysts by their excellent intrinsic catalytic activity. However, the synthesis of 2D TMCs requires prolonged high-temperature conditions or rigorous etching processes. Here we achieved an ultra-fast and facile synthesis of ultra-thin carbon-terminated 2D TMCs via a microwave-pulse sugar-blowing method. A series of 2D TMCs are obtained rapidly within 3 min. This method accurately adjusts carbon-layer thickness and facilitates the formation of 2D structures. Accordingly, the electro catalytic HER activity and stability of TMCs are significantly improved. The 2D W2C with 1 nm carbon-layer thickness shows high HER activity and ultra-long durability (100 h) in both acidic and alkaline electrolytes. Furthermore, this microwave-pulse method is a generic synthesis strategy that is demonstrated by the successful preparation of 2D WC, Mo2C and MoC.
查看更多>>摘要：The control in synthesis and composition plays a vital role in exploring cost-effective efficient electrocatalysts for water splitting. This paper reported a glycerol-assisted solvothermal strategy to synthesize Ru-based electrocatalyst (Ru-G/CC), in-situ growing Eu nanoparticles (NPs) on carbon cloth (CC). The optimal Ru-G/CC exhibits a boosted HER activity (overpotential of 40 mV @ 10 mA cm~(-2), Tafel slope 76 mV dec~(-1)), surpassing benchmark 20 wt% Pt/C; experimental characterization and DFT calculations verified that Ru NPs with a mixed amorphous/crystalline structure in Ru-G/CC effectively decrease the reaction energy barrier in HER. Also, the hydrothermally derived Ru-H2O/CC-350 exhibited a high electrocatalytic OER activity (overpotential of 270 mV @ 10 mA cm~(-2), Tafel slope 63 mV dec~(-1)), exceeding the commercial RuO2. This work provides a successful story via regulating synthetic parameters to design efficient and stable Ru-based electrocatalysts for water splitting.
查看更多>>摘要：To simultaneously enhance the catalytic activity of Pd and lower its dosage, we report a Pd/Co-MOF nanosheets/Ni foam electrode (Pd/Co-MNSs/Ni foam) with conductive 2D MOF nanosheets as interlayer for electrocatalytic hydro dechlorination (ECH). Such electrode delivers high ECH activity for nearly complete dechlorination (-97%) of chloramphenicol (CAP) with an apparent rate constant of 0.11 min~(-1), outcompeting the well-reported and the commercial electrode materials. Pd/Co-MNSs/Ni foam maintains its activity after 9 consecutive runs and 5-day exposure to air, and shows rapid degradation kinetics for other priority contaminants. The formation of Pd/Co-MNSs heterojunction interface increases the electron density of metallic Pd and brings the d states closer to Fermi level than Pd alone, thus optimizing the binding of ECH intermediates. This support construction-based strategy tunes the interface of catalytic electrode to expose active sites and modulate the electronic states of catalyst to promote intrinsic activity, boosting electroreductive remediation of organic halides.
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