查看更多>>摘要：Electrochemical carbon dioxide (CO2) reduction has been studied on a series of copper-bismuth (CuBi) bimetallic catalysts;; however, most of the reported CuBi catalysts tend to exhibit high selectivity towards formate. Here we design four bimetallic CuxBi aerogel electrocatalysts with adjustable composition, which exhibit tunable selectivity for CO2 reduction. The maximum Faradaic efficiency (FE) of CO (86.6%) and formate (60.8%) over Cu_(100)Bi and Cu5Bi is 1.2 and 5.5 times higher than that over the Cu catalyst, respectively. While for Cu_(50)Bi, it shows enhanced selectivity for CH4 (FE=26.0%). The C2H4 FE of Cu_(10)Bi (31.6%) is 1.6 times higher than that of the Cu catalyst. X-ray photoelectron spectroscopy analysis reveals that introduction of different amounts of Bi element leads the variation of Cu(II)/Cu(I) ratios on the catalysts surface, thereby regulating the hydrogenation capability of the reaction intermediates during CO2 reduction.
查看更多>>摘要：Boosting the replacement of traditional NH3 production (Haber-Bosch process) with photocatalytic technology is of great importance for energy and environment remediation. Herein, electron pump strengthened facet engineering is firstly proposed by integration of organic half metallic C(CN)3 on (100) and (110) facet exposed WO3 nanosheets and nanowires. The different built-in electric field is constructed at the interface of the composites. For WO3 nanosheets based WsC, the photoinduced electrons can be directly pumped on the reactive sties of C(CN)3 which performs as the first organic cocatalyst for N2 fixation. While for WO3 nanowires based WwC, the electrons transfer from C(CN)3 to WO3 nanowires, which is unfavorable for the photocatalytic N2 fixation. This process is dedicatedly visualized by Kelvin Probe Force Microscopy (KPFM). As a result, the NH3 evolution yield of optimized WsC reaches 81.9 (imol · g_(cat)~(-1), which is 4.7 folds of the C(CN)3 enwrapped WO3 nanowires (WwC). Moreover, the performance of C(CN)3 surpasses the reported Au, Pt and Ru noble metal cocatalysts. In-situ DRIFTS spectra and DFT calculations also demonstrate the superiorities of C(CN)3 collaborated with facet engineering. This electron pump strengthened facet engineering with C(CN)3 may open up new opportunities for metal-free polymer-based photocatalytic systems for N2 photofixation.
查看更多>>摘要：An effective electrochemical carbon dioxide reduction reaction (eCO2RR) requires the discovery of a catalytic system that is highly active and selective for multi-carbon products together with superior CO2 diffusion at a catalyst layer to minimize the reduction barriers. Here, we found a catalytic system that uses molybdenum phosphide (MoP) nanoparticles covered by imidazolium-fimctionalized ionomer (Im) that promotes CO2 diffusion at the catalyst layer toward the catalyst surface, where CO2 is reduced to ethanol (C2H5OH). The electrochemical results with the MoP-Im co-catalyst show a C2H5OH production Faradaic efficiency and a cathodic energy efficiency of 77.4% and 63.3%, respectively, at a potential as low as - 200 mV vs. RHE. The electrochemical experiments along with our physicochemical characterizations indicate that the Im improves CO2 diffusion and balances water content resulting in a higher CO2-to-water ratio at the catalyst layer and fine-tunes the electronic properties of Mo atoms at the MoP surface. In-situ Raman spectroscopy reveals that a high number of adsorbed *CO intermediates on the surface and a higher binding strength of *CO intermediates on the Mo surface sites in the presence of imidazolium molecules are the main reasons for a superior C-C coupling and thereby the improved C2H5OH formation.
查看更多>>摘要：In this study, we report new electrocatalysts based on 2D anion-intercalated metal hydroxides of Ni(OH)2(NO3)2 (2D NiHN) and its derivation caused by the implantation of single platinum atoms (Pt_(SA)_2D NiHN). The optimum Pt_(SA-1.73)-2D NiHN material having low Pt loading of 1.73 wt% exhibits prospective HER activities with an overpotential (r|) of 24 mV at 10 mA cm~(-2), while the 2D NiNH requires an n of only 280 mV to reach 50 mA cm~(-2) for OER. The assembly of Pt_(SA-1.73)-2D NiHN-based cathode and 2D NiHN-based anode to fabricate a two-electrode electrolyzer of Pt_(SA-1.73)-2D NiHN_(-)//2D NiHN_(+) allows a cell voltage of only 1.45 V at 10 mA cm~(-2) for overall water splitting, superior to RuO2_(2(+))//Pt/C_(-). The device also exhibits prospective long-term stability in 1M KOH. The achievements suggest that the Pt_(SA-1.73)-NiHN and 2D NiHN catalysts are two potential candidates for water splitting application.
查看更多>>摘要：Lattice oxygen mechanism (LOM) is a promising pathway to circumvent sluggish oxygen evolution reaction (OER) for efficient water electrolysis. The iron (Fe)-based oxyhydroxide materials for OER catalysts by LOM is well known. However, dissolution of Fe atoms and promoting participation level of lattice oxygen at a practical and extremely high current density (> 1000 mA cm~(-2) for oxygen generation) should be resolved for high performance and long-term stability. Here, controlling the reduction of synthetic intermediates allowed amorphous BiFe (oxy)hydroxides with secondary bismuth (Bi) metal (BM/BiFeOxHy) heterogeneous structures with abundant lattice vacancies to be obtained. The BM/BiFeOxHy electrode exhibited low overpotential of 232 and 359 mV at a current density of 10 and 1000 mA cm~(-2), respectively. Moreover, the balanced hybridization of Bi/Fe-0 was demonstrated to result in long-term catalytic stability without the dissolution of Fe atoms up to 1000 h at the extremely high current density of 1000 mA cm~(-2) with negligible degradation. We further showed that the excellent performance of the newly proposed BM/BiFeOxHy electrocatalysts is attributed to the utilization of Fe/Bi-O hybridization, the induced amorphous structure, and increased lattice vacancies, which are systematically demonstrated by the electrochemical and physicochemical analysis and theoretical density functional theory (DFT) calculation.
查看更多>>摘要：The activation and ring opening reaction of lactone bond is of great significance in biomass utilization. Cu-based catalysts are widely used in the biomass hydrogenation processes, in which the effect of oxide promoters on Cu catalysts is one of the most attractive research topics. Herein, the transformation of lactones to diols over Cu/Al2O3 and CuLax/Al2O3 catalysts was studied and the promoting role of LaOx has been discussed. The CuLa_(0.25)/Al2O3 catalyst showed outstanding catalytic performance with high 1,4-butanediol yield of > 90 %, and it also showed high efficiency for the hydrogenation of series of five- and six-membered lactones (γ-butyrolactone, γ-valerolactone, δ-hexalactone, etc) to diols. Based on the comprehensive analysis of the XRD, TEM, TPR, XPS, low temperature CO-DRIFT results, the crucial contribution of LaOx species in promoting the selectivity and stability of catalysts were investigated in detail. The presence of LaOx species not only results in the formation of Cu~+-LaOx interfacial active sites, which facilitate the adsorption and activation of lactones, but also promotes the stability of catalyst.
查看更多>>摘要：Photocatalytic cleavage of C-C bond in lignin under mild conditions transforms solar energy into high value-added aromatic compounds. However, the limited understanding of cleavage mechanisms and the catalyst structure-performance relation obstruct the rational design of efficient photocatalysts. Reported herein is the construction of porous carbon nitride (C3N4) with carbon vacancies as heterogeneous photocatalysts via a sequential self-assembly and diol-induced thermal exfoliation. In the photocatalytic cleavage of β-O-4 ether bonds, carbon vacancies in C3N4 can serve as the trapping site to suppress the recombination of photogenerated charge, and endow the C3N4 with high level of N and thus make it easier for the oxidation of Cn-H, contributing to the enhancement of performance. Furthermore, the experimental result and in situ ATR-SEIRAS spectra unveil that O2 could facilitate the cleavage of C-C bond but is not indispensable in this process, which brings new fundamental understanding of β-O-4 bonds cleavage.
查看更多>>摘要：In this work, we elucidated the role of physicochemical textural properties of inert support on the catalyst activity by impregnating Ni on ordered mesoporous silica (SBA-15 and MCM-41) and non-mesoporous silica (nMPS). The catalyst Ni/SBA-15 exhibited the best CO2 conversion (83%) and product selectivity (99.9 %) followed by Ni/MCM-41 and the least by Ni/nMPS. The difference in the nature of the catalyst, degree of nanoparticle distribution and nanoparticle encapsulation by different silica support were studied by N2 adsorption-desorption and X-ray photoelectron spectroscopy (XPS) experiments. The Operando Diffused Reflectance Infrared Fourier Transform Spectroscopy were used to understand the variance in reaction pathway which is accredited to the textural properties of the support. The SBA-15 supported Ni catalyst followed dissociative CO pathway while MCM-41 and nMPS reacted through associative formate mechanism as major pathway. These findings provide a novel perspective on CO2 hydrogenation over Ni-silica, allowing us to tune both activity and selectivity.
查看更多>>摘要：The deep oxidation of toluene is recognized as a major challenge for photocatalytic oxidation of toluene. Herein, we introduced oxygen vacancies into CeO2 nanosheets through novel anion-removal of Ce-LDH, with the calcining temperatures of 750, 850, 950 °C. The photocatalytic toluene performance was ordered by CeMO-850 > CeMO-750 > CeMO-950, and CeMO-850 had better activity than P25, common CeO2, and CeO2-H2. Different reaction pathways were founded on CeMO photocatalysts, i.e., on CeMO-950 and CeMO-750, the cresol and hydroquinone intermediates were observed, which hindered toluene adsorption/activation and were hard to deep-mineralization. Whereas, more benzoic acid, open-loop oxygen-containing intermediates were observed on CeMO-850, which were resulted from its oxygen vacancies (Ov), i.e., surface Ov and Ce~(3+) were beneficial for toluene adsorption, B acid sites and active radicals' generation, respectively, and bulk Ov were helpful for oxygen mobility and efficient deep-mineralization. The mechanism of Ov generation and toluene degradation were proposed.
查看更多>>摘要：The coupling of solar energy conversion and catalytic ozonation is an effective way to eliminate volatile organic compounds with high-efficiency and low-energy-consumption. In this work, we presented a non-noble-metal SiC/CeO2 system for solar-light-assisted catalytic ozonation of toluene. Temperature and light-controlled experiments and atmosphere surface photovoltage measurement were conducted to evaluate photothermal and photoelectric processes. Results show that toluene removal and mineralization efficiencies of 25%SiC-CeO2 were 69.7% and 67.1%, respectively, under full-spectrum illumination with an hourly space velocity of 6000 /h. The SiC enhanced the conversion of incident visible and infrared (IR) light to heat, thereby increasing the reaction temperature over 25%SiC-CeO2- Moreover, SiC transferred electrons to CeO2 in 25%SiC-CeO2, generating more surface Ce~(3+) sites and promoting charge carriers separation efficiency. Given these characteristics, 25%SiC-CeO2 exhibited outstanding performance in toluene mineralization, even better than Pd-loaded CeO2.
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