Anode-Electrolyte Interfacial Acidity Regulation Enhances Electrocatalytic Performances of Alcohol Oxidations.

The local acidity at the anode surface during electrolysis is apparently stronger than that in bulk electrolyte due to the deprotonation from the reactant, which leads to the deteriorated electrocatalytic performances and product distributions. Here, an anode-electrolyte interfacial acidity regulation strategy has been proposed to inhibit local acidification at the surface of anode and enhance the electrocatalytic activity and selectivity of anodic reactions. As a proof of the concept, CeO2-x Lewis acid component has been employed as a supporter to load Au nanoparticles to accelerate the diffusion and enrichment of OH- toward the anode surface, so as to accelerate the electrocatalytic alcohol oxidation reaction. As the result, Au/CeO2-x exhibits much enhanced lactic acid selectivity of 81% and electrochemical activity of 693 mA·cm-2 current density in glycerol oxidation reaction compared to pure Au. Mechanism investigation reveals that the introduced Lewis acid promotes the mass transport and concentration of OH- on the anode surface, thus promoting the generation of lactic acid through the simultaneous enhancements of Faradaic and non-Faradaic processes. Attractively, the proposed strategy can be used for the electro-oxidation performance enhancements of a variety of alcohols, which thereby provides a new perspective for efficient alcohol electro-oxidations and the corresponding electrocatalyst design.

Selective and efficient removal of emerging contaminants by sponge-like manganese ferrite synthesized using a solvent-free method: Crucial role of the three-dimensional porous structure.

Ubiquitous macromolecular natural organic matter (NOM) in wastewater seriously influences the removal of emerging small-molecule contaminants via heterogeneous advanced oxidation processes because this material covers active sites and quenches reactive oxygen species. Here, sponge-like magnetic manganese ferrite (MnFe2O4-S) with a three-dimensional hierarchical porous structure was prepared via a facile solvent-free molten method. Compared with the particle-like structure of MnFe2O4-P, the sponge-like structure of MnFe2O4-S presents an enlarged specific surface area (112.14 m2·g-1 vs. 58.73 m2·g-1) and a smaller macropore diameter (68.2-77.2 nm vs. 946.5 nm). Enlarging the specific surface area increases the exposure of active sites, and adjusting the pore size helps sieve NOM and emerging contaminants. These changes are expected to effectively improve the degradation activity and overcome interference. To confirm the superiority of the sponge-like structure, MnFe2O4-S was used to activate peroxymonosulfate (PMS) for the degradation of multiple emerging contaminants, and its ability to degrade bisphenol A with and without humic acid (HA) was compared with that of MnFe2O4-P. The degradation activity of MnFe2O4-S was 1.6 times greater than that of MnFe2O4-P. Moreover, 20 mg·L-1 HA inhibited the degradation activity of MnFe2O4-S by only 7.1%, which was much lower than that obtained for MnFe2O4-P (53.4%). In addition, the excellent performance was maintained in multiple water matrices. Notably, under lake water matrices, the degradation activity of MnFe2O4-P was inhibited by 35.6% while that of MnFe2O4-S was hardly inhibited. More importantly, the MnFe2O4-S/PMS system was also applicable to the treatment of actual wastewater and 73.0% and 90.1% of total organic carbon and chemical oxygen demand was removed from bio-treated coking wastewater containing non-biodegradable contaminants and NOM. This study provides an alternative route for the green production of high-activity porous spinel ferrites with environmental anti-interference properties.

Zn-Organic Batteries for the Semi-Hydrogenation of Biomass Aldehyde Derivatives and Concurrently Enhanced Power Output.

Electricity generation and chemical productions are both critically important for the sustainable development of modern civilization. Here, a novel bifunctional Zn-organic battery has been established for the concurrent enhanced electricity output and semi-hydrogenations of a series of biomass aldehyderivatives, for the high value-added chemical syntheses. Among them, the typical Zn-furfural (FF) battery equipped with Cu foil-supported edge-enriched Cu nanosheets as cathodic electrocatalyst (Cu NS/Cu foil), provides a maximum current density and power density of 14.6 mA cm-2 and 2.00 mW cm-2 , respectively, and in the meantime, produces high value product, furfural alcohol (FAL). The Cu NS/Cu foil catalyst exhibits excellent electrocatalytic performance of ≈93.5 % conversion ratio and ≈93.1 % selectivity for FF semi-hydrogenation at a low potential of -1.1 V vs. Ag/AgCl by using H2 O as H source, and shows impressive performance for various biomass aldehyderivatives semi-hydrogenation.

Co-doped amorphous NiMoS4 modified with rGO for high-rate performance and long-cycling stability of hybrid supercapacitors.

The electrochemical performance of hybrid capacitors is seriously affected by the slow charging and discharging of the bulk phase. Here, Co-doped amorphous NiMoS4 modified with reduced graphene oxide (rGO) was prepared by a simple one-step hydrothermal method, and the obtained Co-doped NiMoS4/rGO nanocomposite (Ni1-xCoxMoS4/rGO) exhibits a high specific surface area, realizing the redox reaction from the bulk to the surface. Owing to the doping of Co with abundant redox active sites and the support of rGO sheets with high conductivity and a stable structure, the Ni1-xCoxMoS4/rGO anode assembled with an oxidized needle coke (NCO) cathode shows an excellent energy density of 28.9 W h kg-1 at a power density of 968.3 W kg-1. In addition, the hybrid supercapacitor displays a superior cycling performance with a capacity retention of 92.4% after 10 000 cycles. The construction of the Co-doped NiMoS4/rGO nanocomposite provides an effective strategy to boost the activity and stability of amorphous NiMoS4 for high-performance hybrid supercapacitors.

Engineering NiMoO4/NiFe LDH/rGO multicomponent nanosheets toward enhanced electrocatalytic oxygen evolution reaction.

Rational hybridization of two-dimensional (2D) nanomaterials with extrinsic species has shown great promise for boosting the electrocatalytic oxygen evolution reaction (OER). To date, the rational design and engineering of heterojunctions based on three or more components has been rather limited. Herein, by taking advantage of the high intrinsic activity of NiFe layered double hydroxide (LDH), strong synergistic effects between different components, and good electronic conductivity of reduced graphene oxide (rGO), we demonstrate the successful synthesis of NiMoO4/NiFe LDH/rGO nanosheets. As a proof-of-concept demonstration, the multicomponent nanosheet catalyst with a well-modified electronic structure is applied to boost the electrochemical OER and achieve decent electrocatalytic activity in 1 M KOH electrolyte, which can deliver a current density of 10 mA cm-2 with an overpotential of merely 270 mV and a small Tafel slope of 76.2 mV dec-1, which are markedly superior to those of the commercial RuO2 catalyst (303 mV, 131.9 mV dec-1). This work is expected to provide new insights into furnishing multi-component heterostructures with extended functionalities and more advantageous merits.

Engineering Heterostructured Pd-Bi2Te3 Doughnut/Pd Hollow Nanospheres for Ethylene Glycol Electrooxidation.

The electrooxidation of ethylene glycol (EG) is of vital significance for the conversion from biomass energy into electrical energy via direct fuel cells. However, the EG oxidation reaction (EGOR) suffers from poor efficiency due to the limitation of high-performance electrocatalysts for cleaving the C-C bonds. Herein, this limitation is successfully addressed by fabricating the doughnut-shaped Pd-Bi2Te3 heterostructured catalyst. Notably, the heterojunction Pd-Bi2Te3 nanocatalyst has been demonstrated to be highly active toward the EGOR with superb activity and durability, in which a mass activity as high as 2420.8 mA mg-1 is achieved in alkaline media, being 1.7 times higher than that of the commercial Pd/C catalyst. Upon combination of experimental results with mechanism studies, it is indicated that the remarkable EGOR performance is attributed to the enlarged active areas that stemmed from the doughnut-like structure, as well as the strong synergistic effect from Pd-Bi2Te3 and Pd. More importantly, the highly electroactive Pd-Bi2Te3 can accelerate charge transfer and boost the oxidation of CO-like intermediates, which are conducive to the enhancement in electrochemical stability.

Successive Anion/Cation Exchange Enables the Fabrication of Hollow CuCo2S4 Nanorods for Advanced Oxygen Evolution Reaction Electrocatalysis.

Hollow CuCo2S4 nanorods (H-CCS-Ns) have been successfully developed via a facile successive anion/cation-exchange method. The outstanding electrocatalytic performance of H-CCS-Ns is mainly attributed to its distinctive hollow structure, which accelerates the electron transfer rate and provides abundant active sites. Moreover, a mechanism study indicates that H-CCS-Ns has highly active octahedral Co3+, and the existence of Co3+ cations optimizes the adsorption of oxygen-involved intermediates, making H-CCS-Ns a promising OER electrocatalyst. Optimized H-CCS-Ns only need an ultralow overpotential of 220 mV to drive a current density of 10 mA·cm-2 and exhibit distinguished cycling stability with a negligible fluctuation for 30 h. More impressively, when H-CCS-Ns are assembled with Pt/C for overall water splitting, a voltage as low as 1.545 V is required at a current density of 10 mA·cm-2, and the catalyst shows outstanding stability for as long as 38 h. This study offers a feasible strategy to design hollow spinel catalysts for efficient OER catalysis.

Hydrangea-like NiMoO4-Ag/rGO as Battery-type electrode for hybrid supercapacitors with superior stability.

It is a great challenge to design electrode materials with good stability and high specific capacitance for supercapacitors. Herein, a three-dimensional (3D) hydrangea-like NiMoO4 micro-architecture with Ag nanoparticles anchored on the surface has been designed by adding EDTA-2Na, which was assembled with reduced graphene oxide (rGO) and named as NiMoO4-Ag/rGO composite. Benefiting from the synergetic contributions of structural and componential properties, NiMoO4-Ag/rGO composite exhibits a high specific capacitance of 566.4 C g-1 at 1 A g-1, and great cycling performance with 90.5% capacitance retention after 1000 cycles at 10 A g-1. The NiMoO4-Ag/rGO electrode shows an enhanced cycling stability due to the two-dimensional towards two-dimensional (2D-2D) interface coupling between rGO and NiMoO4 nanosheets, and the stable 3D hydrangea-like micro-architecture. Moreover, NiMoO4-Ag/rGO with 5-15 nm pore structure and enhanced conductivity exhibits improved charge transfer and ions diffusion. Besides, NiMoO4-Ag/rGO//AC capacitor displays an outstanding energy density of 40.98 Wh kg-1 at 800 kW kg-1, and an excellent cycling performance with 73.3% capacitance retention at 10 A g-1 after 8000 cycles. The synthesis of NiMoO4-Ag/rGO composite can provide an effective strategy to solve the poor electrochemical stability and slow electron/ion transfer of NiMoO4 material as supercapacitors electrode.

A facile solvothermal syntheses of NiFe layered double hydroxide-Bi2MoO6 heterostructure/reduced graphene oxide with efficient photodegradation for tetracycline.

A heterojunction of NiFe layered double hydroxide (NiFe LDH)-Bi2MoO6 (BMO) loaded on reduced graphene oxide (RGO) sheets was synthesized via an eco-friendly solvothermal reaction. The structural characterization shows that NiFe LDH-BMO heterojunctions are well-distributed on the surface of silk-like transparent RGO sheets. The modification of BMO by NiFe LDH and RGO greatly enhances the photocatalytic performance of BMO for degradation of tetracycline (TC) under visible light. The photocatalyst prepared with 3 wt% RGO shows the highest activity and cycle stability. TC can be completely removed in 80 min, which is about 8.7 times that pure BMO, and showing excellent reusability even after five cycles. The excellent enhancement of photocatalytic performance of NiFe LDH-BMO/RGO composite is attributed to the unique sheet-on-sheet hierarchical heterostructure combined with RGO sheets, facilitating the visible light absorption and photogenerated charge carriers separation.