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The sluggish kinetics of anodic oxygen evolution reaction (OER) is regarded as the main bottleneck for ineffective hydrogen production efficiency, limiting the industrial application of electrochemical water splitting. Substituting the OER by urea electrooxidation reaction (UOR) and simultaneously developing highly active and economical bifunctional electrocatalyst for UOR and hydrogen evolution reaction (HER) is a promising method to realize energy-saving hydrogen production and urea-rich wastewater abatement. Herein, self-supporting Ni-NiO film grown on Ti mesh (Ni-NiO/TM) was successfully prepared by a facile cathodic electrodeposition method with using nickel acetate as the only raw material. Electrodeposition process was optimized by modulating the electrodeposition time and potential. x-ray diffraction, scanning electron microscopy, transmission electron microscopy, x-ray photoelectron spectroscopy and Raman characterization revealed the optimized Ni-NiO/TM was comprised of crystalline Ni and amorphous NiO and its morphology exhibited nanosphere structure, assembled by nanosheets. Ni-NiO/TM sample prepared under the potential of −1.5 V and deposition time of 10 min illustrated the lowest UOR potential of 1.34 V at 50 mA cm−2 and robust stability, superior to the recently reported literatures. Furthermore, the HER potential was only −0.235 V to drive the current density of 50 mA cm−2. The cell voltage of urea-assisted electrolysis for hydrogen production in Ni-NiO/TM||Ni-NiO/TM two-electrode system only required 1.56 V to deliver 50 mA cm−2, obviously lower than that (>1.72 V) for overall water splitting. This work demonstrated the potential of Ni-based material as bifunctional electrocatalyst for energy-saving H2 production by urea-rich wastewater electrolysis. [ABSTRACT FROM AUTHOR]

The strong adsorption of the exsolved A-site of SrCoO2.52 (SC) perovskite with peroxymonosulfate (PMS) makes the effective activation of PMS challenging. A surface reconstruction strategy has been applied to enhance direct electron transfer from the active B-site to PMS. Thus, an interface architecture of Co3O4 nanoparticles in situ growing on the SC perovskite [SrCoO3−δ@Co3O4 (SCC-2)] was developed, which exhibited enhanced catalytic activity. It was found that the surface reconstruction process not only transferred the adsorption site of PMS from the Sr to the Co site, but also enhanced the electron transfer ability of SCC-2. The formed Co–O metal–oxygen bridge facilitated the electron transfer from the bulk SrCoO3−δ to the Co sites of surface Co3O4, thus enhancing the Co2+/Co3+ redox cycle. Compared with pristine SC, the PMS activation improved by 13.1%, and ENR degradation boosted by 1.23 times for SCC-2. This study can provide guidelines to design superior catalysts by surface reconstruction. [ABSTRACT FROM AUTHOR]

Developing a highly efficient Fenton-like catalyst working in a wide pH range is imperative to accomplish its practical wastewater treatment. Herein, FeS2/FeSxOy catalyst was synthesized by hydrothermal-solvothermal vulcanization with thioacetamide as a sulfur source. Characterization results confirmed FeS2/FeSxOy consisted of pyrite, kornelite, and szomolnokite. FeS2/FeSxOy exhibited superior catalytic activity toward H2O2 activation with more than 96% phenol removal within 5 min in pH 3.0 ∼ 8.0 at 30°C. Radical scavenging experiment and EPR analysis revealed both hydroxyl radicals (·OH) and superoxide anion radicals (O2·-) anticipated in phenol elimination, but ·OH played a dominant role. The detailed degradation experiments and density functional theory (DFT) calculation confirmed the vital role of FeS2 in enhancing phenol abatement. This study not only developed a highly active catalyst for H2O2 activation but also theoretically analyzed the FeS2 function in depth, which provided a guide for designing a highly efficient Fenton-like catalyst. [ABSTRACT FROM AUTHOR]

Constructing low cost and efficient electrochemical sensors for highly sensitive detection of hydrazine has a great significance in the field of environmental monitoring and protection. Herein, metal–organic framework derived Co3S4 nanosheets grown on Ti mesh (Co3S4/TM) were successfully synthesized by employing a facile anion exchange reaction and hydrothermal vulcanization with Co-MOF as the precursor. The crystalline structure and morphology of as-synthesized samples were characterized by XRD, SEM, Raman, XPS and TEM analysis. It was found that Co3S4 nanosheets were stacked loosely and irregularly on each other to form a three-dimensional (3D) porous structure. The electrochemical sensing performance of Co3S4/TM toward hydrazine was investigated in 0.1 M NaOH solution. The results showed that Co3S4/TM presented a better electrocatalytic activity toward hydrazine oxidation than Co-MOF/TM and Co(OH)2/TM, owing to the high electrical conductivity of Co3S4 for enhancing electron transfer and the 3D porous structure for providing many more accessible active sites and shortening ion diffusion length as well as promoting mass transfer for hydrazine electrooxidation. As a result, Co3S4/TM exhibited a superior analytical performance with a wide linear range of 0.005–2.0 mM, a high sensitivity of 2956 μA mM−1 cm−2 and a low detection limit of 0.7 μM (S/N = 3), which was superior or comparable to that of the recently reported sensor. Because of the good selectivity and reproducibility, Co3S4/TM was applied to detection of hydrazine in tap water and it showed good recovery, indicating that it could be a promising candidate for analyzing hydrazine in practical application. [ABSTRACT FROM AUTHOR]

Many previous studies have underestimated the role of magnetic components in improving photocatalytic performance. It is significance to explore the migration mechanism of photoinduced carriers in magnetic heterojunction. Here, a magnetic heterojunction, BiOI/BaFe12O19, was synthesized by a simple preparation method. The optimal synthesis conditions and photocatalytic reaction conditions were explored. The growth mechanism of bismuth iodide oxide (BiOI) was elaborated by introducing a micromagnetic field stemming from barium ferrite (BaFe12O19). The electrochemical impedance spectroscopy (EIS), Mott–Schottky curve (MS), transient fluorescence spectrometer (PL), and photocurrent response plot (i ~ t) tests indicated that the BiOI/BaFe12O19 possessed a higher transfer capacity of electrons, higher separation efficiency of photoinduced carriers, stronger photocurrent response, and higher carriers density, compared with pure BiOI. The ultraviolet–visible diffuse reflectance spectrophotometer (UV–vis DRS), electron paramagnetic resonance spectrometer (EPR), MS, and quenching experiments revealed band structure configuration and migration mechanism of photoinduced carriers. The enhancement mechanism of photocatalysis and photocatalytic reaction mechanism was clearly proclaimed in BiOI/BaFe12O19 catalytic system. [ABSTRACT FROM AUTHOR]

A heterostructure α-Fe2O3/SiC (FS) was designed by depositing α-Fe2O3 nanotubes on the surface of SiC through a facile hydrothermal method. Microstructure and photocatalytic activity of the hybrid were analyzed via various characterization techniques including XRD, TEM, UV–Vis DRS, PL, XPS, and electrochemical tests. The photocatalytic efficiencies of the α-Fe2O3/SiC heterojunction, individual SiC, and α-Fe2O3 were evaluated by measuring photo-Fenton degradation and photocatalytic hydrogen production. The FS hybrid exhibited a much higher photocatalytic efficiency than the individual ones. The results revealed that the cooperation of α-Fe2O3 and SiC led to synergy effects of the two separate semiconductors. The photocatalytic enhancement can be attributed to the strong light-harvesting capability, close contact interface, improved dispersion and predominant (104) active facet exposure of α-Fe2O3, as well as efficient electron-hole transfer and separation. The photocatalytic mechanism analysis reveals that the charge-carrier transportation of the α-Fe2O3/SiC heterojunction follows a direct Z-scheme preserving the high-energy electrons and holes. The photocatalytic charge-carrier transportation of the constructed α-Fe2O3/SiC heterojunction follows a direct Z-scheme preserving the high-energy electrons and holes. [ABSTRACT FROM AUTHOR]

Exploiting cost-effective, highly efficient and stable alkaline electrocatalysts is a great challenge for the hydrogen evolution reaction (HER). Herein, NiMoO4 and CoFe layered double hydroxide (CoFe LDH) with poor crystallinity were successively deposited on Cu nanowire (Cu NW) grown on Cu foam by a two-step electrodeposition process, which was verified by XRD, Raman, ATR-FTIR, XPS, SEM, TEM and HRTEM characterizations. The HER performance measurement in 1.0 M KOH solution showed the optimal CoFe LDH-60 s/NiMoO4/Cu NW/Cu foam sample demonstrated prominent alkaline HER activity and long-term durability with an ultralow overpotential of 45 mV at −10 mA cm−2 and a Tafel slope of 94.0 mV dec−1, superior to the recently reported transition metal-based electrocatalysts. Further study clarified that the remarkable alkaline HER performance could be attributed to the strong synergistic effect between CoFe LDH-60 s and NiMoO4 in favor of water adsorption/activation and optimizing hydrogen adsorption, and providing plentiful exposed active sites as well as an enhanced electron transfer process offered by the unique 1D nanostructure with Cu nanowire as the core. This work can provide a guidance for designing a highly active and stable electrocatalyst for hydrogen production. [ABSTRACT FROM AUTHOR]

Developing a cost-effective and efficient bifunctional electrocatalyst with simple synthesis strategy for hydrazine sensing and H evolution reaction (HER) is of utmost importance. Herein, a three-dimensional porous Cu-doped metallic Ni coating on Ti mesh (Ni(Cu) coating/TM) was successfully electrodeposited by a facile electrochemical method. Electrochemical etching of the electrodeposited Ni(Cu) coating with metallic Ni and Cu mixed phase on a Ti mesh contributed to the formation of a three-dimensional porous Cu-doped metallic Ni coating. Owing to the large specific surface area and enhanced electroconductivity caused by the porous structure and Cu doping, respectively, the developed Ni(Cu) coating/TM exhibited superior hydrazine sensing performance and electrocatalytic activity toward hydrogen evolution reaction (HER). The Ni(Cu) coating/TM electrode presented a good sensitivity of 3909 μA mM−1 cm−2 and two relatively broad linear ranges from 0.004 mM to 2.915 mM and from 2.915 mM to 5.691 mM as well as a low detection limit of 1.90 μM. In addition, the Ni(Cu) coating/TM required a relatively low HER overpotential of 140 mV to reach −10 mA cm−2 and exhibited robust durability in alkaline solution. The excellent hydrazine electrooxidation and HER performance guarantee its promising application in hydrazine detection and energy conversion. [ABSTRACT FROM AUTHOR]

Higher water dissociation (Volmer step) energy barrier leads to the sluggish alkaline hydrogen evolution reaction (HER) rate. Since hydrophilic TiO2 can reduce water dissociation barrier while the widely studied Ru has nearly zero hydrogen adsorption Gibbs free energy, the combination of TiO2 and Ru/C might collectively enhance Volmer and Heyrovsky/Tafel step and finally promote HER performance. Herein, Ru/C−TiO2 with average size of 3.6 nm for Ru was synthesized by a two‐step process. It presented superior alkaline HER activity with η10 of 44 mV, better than that of Ru/C (107 mV), Pt/C (84 mV) and C−TiO2 with negligible activity. The prominent HER performance was due to synergistic effect between TiO2 and Ru, which greatly expedited water dissociation for intermediate hydrogen production and the following electrochemical hydrogen desorption for producing H2. This work combines specific active sites for different elementary steps and then boosts alkaline HER performance, which provide a guide for designing efficient and stable HER electrocatalyst. [ABSTRACT FROM AUTHOR]

The selective crystal facet growth of BiOX (X = Cl, Br, I) is very significant since each facet possesses different physicochemical properties. In this study, polyvinylpyrrolidone (PVP), a structure directing agent, was unprecedentedly introduced to modulate the crystal facet growth of BiOX to obtain BiOX/PVP with more (110) active facet exposure, for the first time. The exposure of the (110) crystal surface of BiOX due to the introduction of PVP is comprehensively explained at the molecular level. A possible application is the photodegradation of dyes, such as rhodamine B (RhB), from wastewater as more superoxide radicals are generated compared to the pure BiOX sample under identical visible light irradiation conditions. According to first-principles calculations, the (110) crystal face has a higher electron density, allowing it to generate free electrons more easily. In comparison with pure BiOCl, a higher (110) active facet exposure for BiOCl/PVP prolonged the lifetimes of photoinduced carries and enhanced the photocatalytic activity. Herein, the enhancement mechanism of photoactivity was explained via various experiments and theoretical calculations in detail. [ABSTRACT FROM AUTHOR]

At present, dye wastewater is the most difficult industrial wastewater to treat. Photocatalytic degradation of dye wastewater under visible light irradiation is the most potential method. Magnetic photocatalytic material is a very good choice because of its easy separation and without secondary pollution. Based on a comparative study between α-Bi2O3 and β-Bi2O3, β-Bi2O3/SrFe12O19 magnetic photocatalyst was prepared to aim at rhodamine B(RhB) photodegradation. The photodegradation rate of RhB reaches 92.97% after 150 min photocatalytic reaction under visible light irradiation. We hope that this work can provide a reference for dye wastewater treatment. [ABSTRACT FROM AUTHOR]

The Co-doped SrFe12O19 with small particle size was successfully synthesised via a hydrothermal method for the first time. XRD test indicated that the Co incorporation did not alter the M-type structure for SrFe12O19. Meanwhile, a novel nano-magnetic heterostructure BiOCl/Co-doped SrFe12O19 (BiOCl/SrFe12-xCoxO19) was also synthesised using same method. The heterostructure possessed a low bandgap energy and stable magnetic property. The photocatalytic activity evaluation illustrated that the photodegradation efficiency of Rhodamine B (RhB) reached to 98% after 100-min photocatalytic reaction. Furthermore, RhB photodegradation efficiency using BiOCl/SrFe12-xCoxO19 was still more than 70% after four times reuse. The photocatalytic mechanism was explained in detail. The application of BiOCl/SrFe12-xCoxO19 into the removal of organic contaminants or the control of environmental pollution will be of great value. The research results are beneficial to the promotion of industrial applications of solid-state composites in the fields of environmental engineering and energy utilisation. [ABSTRACT FROM AUTHOR]

We synthesized a flower-like Ni–Mn–S structure on Ti mesh (Ni–Mn–S/TM) as a monolithic sensing platform by a facile electrodeposition method. The phase composition and surface morphology of the as-prepared samples were characterized by XRD, XPS, SEM, TEM and HRTEM. The electrodeposits displayed a unique hierarchical nanosheet structure. Mn incorporation remarkably modulated the surface morphology of Ni–S on TM. This flower-like structure could increase the active surface area, providing more active sites for the electrocatalytic reaction. Electrochemical measurement demonstrated that Ni–Mn–S/TM exhibited good response to glucose in the range of 12 μM to 3.5 mM with a high sensitivity of 860.8 μA mM−1 cm−2. The binder-free Ni–Mn–S/TM electrode also presented good anti-interference ability, reusability and stability. This work gives a new avenue to improve the glucose sensing performance of nickel sulfide and even other nanomaterials. [ABSTRACT FROM AUTHOR]

Mn1-xZnxFe2O4 (Mn-Zn ferrite) and S2O82-/ZrO2-Mn1-xZnxFe2O4 were synthesised by soaking-calcination method and chemical coprecipitation approach, respectively. The optimal synthesis conditions of S2O82-/ZrO2- Mn-Zn ferrite were as follows, 25% mass ratio of Mn-Zn ferrite to ZrO2, (NH4)2S2O8 solution of 0.4 mol/L and the calcination temperature of 600℃. The as-synthesised composite with the nano size of the particles possessed excellent catalytic activity for esterification reaction under 78℃. The largest yield of ethyl acetate using the as-prepared magnetic solid acid catalyst was 78.6%, while the yield was only 66.7% using (NH4)2S2O8 catalyst in the esterification reaction. The recovery ratio of the magnetic catalyst S2O82-/ZrO2- Mn-Zn ferrite was still more than 80% after 3rd cycles, which facilitated to promote the scale application of magnetic solid acid catalyst. [ABSTRACT FROM AUTHOR]

Three-dimensional interconnected Co(OH)2 nanosheets (Co(OH)2 NS) were electrodeposited onto a Ti mesh (TM) surface, which was demonstrated by XRD, Raman spectroscopy, XPS and SEM characterization. The electrochemical sensing performance of the Co(OH)2 NS/TM toward hydrazine was investigated by cyclic voltammetry and amperometric techniques in a 0.1 M NaOH aqueous solution. The as-prepared Co(OH)2 NS/TM with an electrodeposition time of 10 min exhibited prominent capacity to detect hydrazine with a wide linear range from 5 μM to 3.0 mM and limit of detection (LOD) of 1.98 μM. Co(OH)2 NS/TM electrodes also showed a high sensitivity of 2793.9 μA mM−1 cm−2, excellent selectivity, reproducibility, appreciable stability with a RSD less than 3.5%, as well as the high recovery of hydrazine in real samples, indicating its potential application in real sample analysis. [ABSTRACT FROM AUTHOR]