Search

Rational design and synthesis of multimetallic nanostructures (NSs) are fundamentally important for electrochemical CO2 reduction reaction (CO2RR). Herein, a multi-step seed-mediated growth method is applied to synthesize asymmetric AuAgCu heterostructures using Au nanobipyramids as nucleation seeds, in which their composition and structures are well controlled. We find that the selectivity of C2 products for CO2RR could be effectively regulated by tandem catalysis and electronic effect over trimetallic AuAgCu heterostructures. Particularly, the Faraday efficiency toward ethanol could reach up to 37.5% at a potential of −0.8 V versus reversible hydrogen electrode over asymmetric Au1Ag1Cu5 heterostructures with segregated domains of three constituent metals. This work provides an efficient strategy for the synthesis of multicomponent architectures to boost their promising application in CO2RR. [ABSTRACT FROM AUTHOR]

Electrochemical CO2 reduction reaction (CO2RR) is an attractive pathway for closing the anthropogenic carbon cycle and storing intermittent renewable energy by converting CO2 to valuable chemicals and fuels. The production of highly reduced carbon compounds beyond CO and formate, such as hydrocarbon and oxygenate products with higher energy density, is particularly desirable for practical applications. However, the productivity towards highly reduced chemicals is typically limited by high overpotential and poor selectivity due to the multiple electron-proton transfer steps. Tandem catalysis, which is extensively utilized by nature for producing biological macromolecules with multiple enzymes via coupled reaction steps, represents a promising strategy for enhancing the CO2RR performance. Improving the efficiency of CO2RR via tandem catalysis has recently emerged as an exciting research frontier and achieved significant advances. Here we describe the general principles and also considerations for designing tandem catalysis for CO2RR. Recent advances in constructing tandem catalysts, mainly including bimetallic alloy nanostructures, bimetallic heterostructures, bimetallic core-shell nanostructures, bimetallic mixture catalysts, metal-metal organic framework (MOF) and metal-metallic complexes, metal-nonmetal hybrid nanomaterials and copper-free hybrid nanomaterials for boosting the CO2RR performance are systematically summarized. The study of tandem catalysis for CO2RR is still at the early stage, and future research challenges and opportunities are also discussed. [ABSTRACT FROM AUTHOR]

Electrochemical reduction of CO2 into value‐added chemicals provides a promising approach to mitigate climate change caused by CO2 from excess consumption of fossil fuels. As the CO2 molecule is chemically inert and the reaction kinetics is sluggish, efficient electrocatalysts are thus highly required for promoting the conversion of CO2. With great efforts devoted to improving the catalytic performance, the development of electrocatalysts for CO2 reduction has gone from bulk metals with poor control to nanostructures with atomic precision. Nanostructured electrocatalysts with atomic precision are believed to be capable of combining the advantages of heterogeneous and homogenous catalysts. In this review, the recent advances in designing nanostructured electrocatalysts at the atomic level for boosting the catalytic performance toward CO2 reduction and revealing the structure–property relationship are summarized. The challenges and opportunities in the near future are also proposed for paving the development of electrocatalytic CO2 reduction. [ABSTRACT FROM AUTHOR]

The design of efficient mixed Mn–Co oxides as oxygen reduction reaction (ORR) electrocatalysts in alkaline media has been boosted nowadays. Recently, multivariant MOFs have been demonstrated as versatile precursors to construct these mixed metal oxides. Herein, we synthesized four mixed Mn–Co oxide samples via simply annealing their MIL-53 precursors with different Co/Mn molar ratios. These four samples were dominated by three kinds of Mn–Co spinel phases. The mixed Mn–Co oxides showed enhanced ORR performances compared with the single metal counterparts in alkaline media. In particular, the sample containing a pure MnCo2O4 phase exhibited the highest activity with a half-wave potential of 0.772 V (vs. RHE), only 40 mV negative compared with that of commercial Pt/C. The H2O2 yield was calculated to be below 12.1%, corresponding to the high diffusion-limited current density along with the high electron transfer number. The surface defects, active Mn4+/Mn3+ and electrochemically active surface area together affected the ORR performances of these mixed Mn–Co oxides. The present work highlights the facile controllability of divalent MIL-53 analogues for highly efficient mixed Mn–Co oxides in ORR electrocatalysis. [ABSTRACT FROM AUTHOR]

• A novel phosphonate complex is designed through the coordination of Coni-Bimetal centers and P contained ligands (1-hydroxyethylidene-1,1-diphosphonic acid). • P element in the organic ligands of CoNi-HEDP could in situ phosphorize the Co/Ni sites and carbon atoms. • (Co 0.6 Ni 0.4) 2 P@PC exhibits high activities towards both cathodic hydrogen evolution and anodic hydrazine oxidation. • Solar-power-assisted (Co 0.6 Ni 0.4) 2 P@PC-OHzS device could continuously produce H 2 and N 2 with a voltage of 0.048 V. Electrochemical water splitting is considered as a sustainable and clean technology for hydrogen production, but is still limited by the sluggish kinetics of anodic oxygen evolution reaction (OER). Hydrazine oxidation reaction (HzOR) requires much lower thermodynamic oxidation potential and produces zero-carbon molecules, thus becoming a promising alternative to replace OER for realizing energy-saving hydrogen production. Herein, a CoNi-bimetal phosphide nanoparticles embedded P doped carbon matrix structure ((Co 0.6 Ni 0.4) 2 P@PC) is constructed via annealing a novel precursor composed of CoNi-bimetal sites and P contained ligands for hydrazine-assisted water splitting. The P element can simultaneously in situ phosphorize the metal sites and carbon atoms. The (Co 0.6 Ni 0.4) 2 P@PC exhibits outstanding hydrogen evolution reaction (HER) performance with an overpotential of 67.9 mV at 10 mA cm−2 and requires an ultralow potential of -83 mV at 10 mA cm−2 for HzOR in alkaline electrolyte. Furthermore, the electrolyzer assembled with the (Co 0.6 Ni 0.4) 2 P@PC as both cathode and anode delivers a cell voltage of merely 0.048 V which is much lower compared with the OER-HER system (1.60 V) for reaching 10 mA cm−2. The present work develops an eco-friendly synthetic method for designing low-cost and highly efficient carbon matrix incorporated phosphide electrocatalyst for energy-saving hydrogen production. Presented here is a facile, eco-friendly and cost effective strategy for fabricating a CoNi-bimetal phosphide embedded carbon matrix structure ((Co 0.6 Ni 0.4) 2 P@PC) derived from a novel phosphonate complex. The (Co 0.6 Ni 0.4) 2 P@PC exhibits high activity and robust stability for hydrazine-assisted electrolytic hydrogen production. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: In this study, TiO2 nano-particles decorated TiO2 nano-tubes arrays (TiO2 NPs/TiO2 NTAs) photoelectrodes have been successfully prepared through anodization, combined with ultrasonic strategy, followed by annealing post-treatment. The morphology and structure of the as-prepared TiO2 NPs/TiO2 NTAs photoelectrodes were characterized by scanning electrons microscopy (SEM), N2 adsorption/desorption isotherms, X-ray diffraction (XRD) and UV–visible light diffuse reflection spectroscopy (DRS). In addition, the generation of hydroxyl radicals ( OH) was detected by a photoluminescence (PL) spectra using terephthalic acid (TA) as a probe molecule. Furthermore, the photoelectrochemical (PECH) properties of TiO2 NPs/TiO2 NTAs photoanode were investigated through transient open circuit potential (OCP), photocurrent response (PCR) and electrochemical impedance spectroscopy (EIS). It was found that TiO2 NPs/TiO2 NTAs photoelectrode exhibited a distinct decrease of OCP of −0.219mVcm−2 and PCR of 0.049mAcm−2, while a significantly enhanced photoelectrocatalytic (PEC) efficiency of 63.6% (0.4V vs. SCE) for the degradation of diclofenac. Moreover, the enhanced PEC mechanism of TiO2 NPs/TiO2 NTAs photoanode was proposed. The high PEC performance could be attributed to the decoration of TiO2 NPs, which could improve the mobility and separation efficiency of photoinduced charge carriers under external potential. [Copyright &y& Elsevier]

Abstract: Palladium nanoparticles electrolytic deposited onto preformed electrodes coated with polymer film was used as cathode for the electrocatalytic hydrodechlorination of dichlorophenol in aqueous solution. The surface of the electrode substrates was coated with a polypyrrole (PPY) film electropolymerized via potentiostatic method. The FT-IR results indicated that the peaks at 1550, 1190 and 960cm−1 were ascribed to the characteristic bands of PPYs. SEM images performed that the Pd nano-particles were uniformly dispersed on the composite electrode after modification with PPYs. Moreover, the nucleation and growth of PPY in NaClO4 was much faster than that of others from the chronoamperometry analysis. XRD and XPS results indicated that Pd existed mainly as Pd0. TEM results showed that Pd particles were well dispersed with an average diameter of 10nm. The effects of the dopant ions, applied potential, temperature, and reaction time of potentiostatic electropolymerization on the composite electrode for the electrochemical hydrodechlorination of 2,4-dichlorophenol (2,4-DCP) were examined. Under optimal conditions, a 90.9% removal rate for 2,4-DCP could be achieved with the use of the Pd/PPY(PTS)/Ni composite electrode. The process of 2,4-DCP dechlorination was investigated. [Copyright &y& Elsevier]

Palladium-polypyrrole-foam nickelcomposite electrode (Pd/PPY(PTS)/Ni) was prepared throughelectrodeposited of palladiumnanoparticles onto preformed electrodes (surface of electrodes wascoated with potentiostatic electropolymerized polypyrrole). The stabilityof the fresh and used composite electrode was characterized by scanningelectron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectronspectroscopy (XPS). It was found that the surface state, morphology,and crystalline structure of the composite electrode were stable after5 recycle uses. Electrocatalytic activity of the composite electrodewas evaluated for the hydrodechlorination (ECH) of six kinds of dichlorophenols(DCPs). Results indicated that 2,4-DCP showed higher hydrodechlorinationrate. Further, the pathway of electrochemical hydrodechlorinationof six kinds of dichlorophenol isomers was investigated. [ABSTRACT FROM AUTHOR]

Abstract: In the present work, the effect of molecular structures of di- and tri- nitrophenols on electrochemical degradation has been investigated on Bi-doped lead dioxide electrodes in terms of cyclic voltammetry and bulk electrolysis. The results of SEM and AFM displayed a porous structure with small-sized crystal particles and compact crystalline structure of Ti/Bi-PbO2. These nitrophenols were believed to be mainly degraded by means of indirect oxidation due to the low anodic oxidation currents observed in cyclic voltammetries and large amount of oxidants. And the absence of polymeric adhesive compounds formed and deposited on the surface of electrodes indicated the high electrocatalytic activity of Ti/Bi-PbO2 for decomposing organics. Within the present experimental conditions used, almost complete elimination of nitrophenols was achieved. The electrochemical oxidation of them followed in the order: 2,6-dinitrophenol>2,5-dinitrophenol>2,4-dinitrophenol>2,4,6-trinitrophenol. The relationship between electrochemical oxidation rate and the molecular structure of nitrophenols was discussed. The results of LC/MS and HPLC suggested that three kinds of intermediates were generated, i.e., polyhydroxylated intermediates, reduction products of nitrophenols and carboxylic acids. The possible degradation pathways of nitrophenols were proposed. The denitration and substitution by hydroxyl radicals on aromatic rings seemed to be the first stage. As a consequence, the formation of polyhydroxylated intermediates took place. These compounds were successively oxidized into catechol, resorcinol and hydroquinone, as well as reduced to aminophenols, followed by the opening of aromatic rings and the formation of a series of carboxylic acids. Finally, these carboxylic acids were oxidized into CO2 and H2O. [Copyright &y& Elsevier]

[Display omitted] • BiOCl nanoplates derived 2D Bi nanosheets electrocatalysts demonstrate a maximum Faradic efficiency (FE) of 92 % at −0.9 V vs. reverse hydrogen electrode (RHE) with a current density of 10.5 mA cm−2. • In addition, BiOBr nanoplates derived catalysts also exhibit a maximum FE of above 90 % at −0.9 V and FEs of over 80 % in a wide potential window (−0.8 to −1.2 V) are obtained. • BiOBr and BiOCl nanoplates precursors with optimal range of thicknesses and sizes can provide stronger adsorption affinity of CO 2 − lower contact resistance and enlarged electrochemical active surface area during the electrochemical CO 2 and hence accelerates reaction kinetics and activity due to its 2D structures. Electroreduction of carbon dioxide (CO 2) into formic acid (HCOOH) or formate can alleviate energy crises and simultaneously decrease the content of one of the main greenhouse gases. Herein, two-dimensional (2D) Bi nanosheets electrocatalyst can be obtained via in situ transformations from optimized thickness and sizes of the bismuth oxychloride (BiOCl) precursors while the precursors with improper thicknesses or sizes were electeoreduced into nanoparticles. The 2D Bi nanosheets derived from BiOCl nanoplates precursors which were synthesized with solvent of EG/H 2 O (1:1) show CO 2 reduction reaction (CO 2 RR) activity with high selectivity (92 % at −0.9 V vs reversible hydrogen electrode (RHE)), and high stability (15 h) with a current density of 10.5 mA cm−2. In addition, FEs over 80 % in a wide potential window (−0.8 to −1.3 V) are obtained in an optimal range of thickness (20∼25 nm) and sizes (40∼497 nm). This work shows that the optimal thicknesses and sizes of BiOX (X = Br, Cl) nanoplates derived Bi can maintain the 2D structures and the excellent electrocatalytic activity in CO 2 RR might be attributed to more exposed active sites, enhanced electrochemical active areas, and lowered contact resistance. Furthermore, the in situ transformed electrocatalysts from the BiOX precursors is a promising and general way for regulating the activity and selectivity for CO 2 reduction to formate. [ABSTRACT FROM AUTHOR]

Electrochemical nitrogen reduction reaction (NRR) to ammonia (NH 3) is considered as a promising alternative for the traditional Haber-Bosch process due to its lower energy consumption under ambient conditions. However, major obstacles still remain in improving the NRR activity and selectivity, mainly arising from the chemical inertness of N 2 molecule, the sluggish reaction kinetics, and the competition between hydrogen evolution reaction (HER) and NRR. The defect engineering can regulate and modify the local coordination environment of electrocatalysts, which could be considered as effective strategies to promote the intrinsic activity. In this review, recent advances on defect engineering of nanostructured electrocatalysts for NRR, including vacancy, doping, single atom, amorphization and high-index facet, are summarized. Particularly, the strategies of defect engineering, the reaction mechanisms, and the reliable NH 3 detection methods, are systematically discussed. Finally, the opportunities and challenges towards the rational design and synthesis of advanced electrocatalysts with controlled defects for NRR are proposed. Recent advances on defect engineering for nitrogen reduction reaction (NRR), including vacancy, doping, single atom, amorphization and high-index facet, are summarized. Image 1 • The recent achievements of NRR electrocatalysts with various defect structure have been summarized. • The principles of each defect engineering strategy and the existing problems have been analyzed in detail. • The reaction mechanisms for the reduction of N 2 to NH 3 on the heterogeneous surfaces have been systematically disscussed. • The methods of ammonia detection and the ways to improve the reliability of nitrogen reduction research have been disscussed. [ABSTRACT FROM AUTHOR]

Atomically Thin Catalysts: Recent Advances in Atomic-Level Engineering of Nanostructured Catalysts for Electrochemical CO2 Reduction (Adv. Funct. Keywords: atomically thin catalysts; CO2 reduction; electrocatalysis EN atomically thin catalysts CO2 reduction electrocatalysis 1 1 1 04/29/20 20200427 NES 200427 In article number 1910534, Huiling Liu, Zhicheng Zhang, and co-workers summarize the recent advances in designing nanostructured electrocatalysts at the atomic level for boosting the catalytic performance toward CO SB 2 sb reduction. Atomically thin catalysts, CO2 reduction, electrocatalysis. [Extracted from the article]

Abstract: Nitrogen doped TiO2/Ti photoelectrodes were prepared by a sequence of anodization and plasma based ion implantation (PBII). The properties of this photoelectrode were characterized by scanning electronic microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), X-ray photoelectron spectrometry (XPS), Ultra violet/visible light diffuse reflectance spectra (UV/vis/DRS), surface photovoltage (SPV), etc. Photoelectrocatalytic (PEC) performance of N-doped TiO2/Ti photoelectrode was tested under visible light irradiation. Their photocatalytic activity was evaluated by degradation of Rhodamine B (Rh.B). The results of XPS showed that nitrogen element was in form of three species, i.e. β-N, molecular γ-N and O–Ti–N, which existed in the lattices of TiO2 and gaps between molecules. The results of UV/vis/DRS spectra and SPV revealed that proper doping of nitrogen could expand the response of photoelectrodes towards visible light and diminish the recombination of photo-generated holes and electrons, respectively. The photoelectrocatalytic activity of N-doped TiO2/Ti photoelectrodes was superior to those of undoped one under visible light region irradiation. [Copyright &y& Elsevier]