Fabrication of sandwich structured C/NiO/TiO2 nanotube arrays for enhanced electrocatalytic activity towards hydrogen evolution

Onion-Ring-like Carbon and Nitrogen from ZIF-8 on TiO2/Fe2O3 Nanostructure for Overall Electrochemical Water Splitting

The carbon and nitrogen derived from ZIF-8 embedded in TiO₂/Fe₂O₃ (i.e., C,N-ZIF/TiFe) nanostructures exhibit superior electrocatalytic performance toward oxygen evolution reactions (OER), hydrogen evolution reactions (HER), and overall H₂O splitting. The results showed that the C,N-ZIF/TiFe nanostructure was the best catalyst in comparison to ZIF/TiFe and TiFe nanostructures toward HER and OER. These results revealed that combining the highly active carbon and nitrogen from ZIF-8 with a TiO₂/Fe₂O₃ semiconductor enriched the overall H₂O splitting. A possible OER mechanism is attributed to some groups that support the surface active site of the catalyst and adsorbent intermediate species. Finally, this inexpensive electrocatalyst was synthesized without noble metals and showed superior electrocatalytic activity and great stability with the potential to achieve ground-breaking and novel applications in fuel cells.

Free-standing TiO2 nanotubes decorated with spherical nickel nanoparticles as a cost-efficient electrocatalyst for oxygen evolution reaction

Here, we report significant activity towards the oxygen evolution reaction (OER) of spherical nickel nanoparticles (NPs) electrodeposited onto free-standing TiO2 nanotubes (TNT) via cyclic voltammetry. It has been shown that simple manipulation of processing parameters, including scan rate and number of cycles, allows for formation of the NPs in various diameters and amounts. The polarization data with respect to transmission electron microscopy (TEM) allowed for determination of the diameter and propagation depth of the Ni NPs leading to the highest activity towards the OER with an overpotential of 540 mV at +10 mA cm-2 and Tafel slope of 52 mV per decade. X-ray photoelectron spectroscopy (XPS) indicates the presence of structure defects within Ni NPs whereas Mott-Schottky analysis provides information on the anodically shifted flat band potential and highly increased donor density. The obtained results along with literature studies allowed a proposal of the origin of the enhancement towards the OER. We believe that combination of transition metal-based NPs and TNT provides valuable insight on efficient and low-cost electrocatalysts.

Improving sensitivity of antimicrobial drug nitrofurazone detection in food and biological samples based on nanostructured anatase-titania sheathed reduced graphene oxide

In this study, we have prepared anatase titanium (IV) oxide warped reduced graphene oxide nanocomposites (TiO₂-rGO NC) using ultrasonic methodology. The morphology of the TiO₂-rGO NC was studied using FESEM and TEM. In addition, XRD, Raman, thermogravimetric analysis (TGA) and XPS are used to analyze the crystallinity and chemical composition of the TiO₂-rGO NC. We have also investigated the electrochemical behavior of the as-prepared NCs with electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and different pulse voltammetry techniques (DPV). The TiO₂-rGO NC modified electrode shows the lower charge transfer resistance (R _ct ) of 62.87 Ω. Next, the glassy carbon electrode (GCE) was modified with sonochemically prepared TiO₂-rGO NC and used to determine the electrocatalytic reduction of nitrofurazone (NTF). Thus, the proposed sensor established the wider covering range (WCR) of 0.01 to 380 µM and an excellent detection limit of 2.28 nM. Finally, the TiO₂-rGO NC/GCE was applied to determine the NTF in real samples, including crayfish and human blood serum samples, which acquired good found and recovery values.

Ultrahigh electrocatalytic activity with trace amounts of platinum loadings on free-standing mesoporous titanium nitride nanotube arrays for hydrogen evolution reactions

Minimizing Pt loadings on electrocatalysts for hydrogen evolution reactions (HERs) is essential for their commercial applications. Herein, free-standing mesoporous titanium nitride nanotube arrays (TiN NTAs) were fabricated to serve as a substrate for Pt loadings in trace amounts. TiN NTAs were prepared by thermal treatment of anodic TiO2 NTAs at 750 °C for 3 h in a NH3 atmosphere. The uniform TiN NTAs showed an inner diameter of ∼80 nm and a length of ∼7 μm, with many mesoporous holes ranging from 5 to 10 nm in diameter on the nanotube walls. Pt species dissolved from the Pt counter electrode in electrochemical cycling were redeposited on the mesoporous TiN NTAs to produce Pt-TiN NTAs with an ultra-low Pt loading of 8.3 μg cm-2. Pt-TiN NTAs exhibited 15-fold higher mass activity towards HER than the benchmark 20 wt% Pt/C in acidic media, with an overpotential of 71 mV vs. RHE at a current density of 10 mA cm-2, a Tafel slope value of 46.4 mV dec-1 and excellent stability. The performance of Pt-TiN NTAs is also much better than that of Pt species deposited on non-mesoporous nanotube arrays due to the shortcuts originating from the mesoporous holes on the nanotube walls for electron and mass transfer.

A microbial fuel cell system with manganese dioxide/titanium dioxide/graphitic carbon nitride coated granular activated carbon cathode successfully treated organic acids industrial wastewater with residual nitric acid

To meet the urgent demands for sustainable and efficient, environmental-friendly wastewater treatment, a Microbial fuel cell reactor system with MnO₂/TiO₂/g-C₃N₄ (manganese dioxide/ titanium dioxide/graphitic carbon nitride) @GAC (granular activated carbon) electrode was developed. It was both efficient and energy-saving in treating organic acid wastewater generated in Nylon production, with high-concentration COD and residual nitric acid. The MnO₂/TiO₂/g-C₃N₄ catalyst was deposited on GAC via in-situ growth and sol-gel method. The COD, NH₄⁺-N and NO₃^--N was efficiently removed (respectively 98%, 99% and 99%). The COD removal capacity (17.77 kg COD m^-3d^-1) and the maximum power density (1176.47 mW m^-3) was respectively 36.83% and 65.29% higher than the GAC cathode system. The anodic and cathodic microbial consortiums in MFC were analyzed and compared. The MnO₂/TiO₂/g-C₃N₄@GAC MFC system is technically feasible and cost-effective in treating industrial wastewater.

Transition metal mixed oxide-embedded graphene oxide bilayers as an efficient electrocatalyst for optimizing hydrogen evolution reaction in alkaline media

A novel electrocatalyst containing different percentages of iron-titanium mixed oxide onto graphene oxide (GO) support was prepared by embedding via the thermal decomposition method (TD) and was coated on a Cu substrate through facile electroless Ni–Co–P plating.

Efficient photoelectrochemical water-splitting over carbon membrane linked Au and TiO2 nanotube arrays film based on multiple carriers transport paths

Herein, a carbon membrane and Au nanoparticles were combined to improve the efficiency of photoelectrocatalytic water splitting over a TiO₂ nanotube arrays film (TiO₂ NTAF). Two different ternary nanostructures were constructed by hydrothermal and photochemical deposition processes. One was carbon membrane bridged Au nanoparticles and TiO₂ nanotube arrays (Au/C/TiO₂ NTAF), while the other was Au nanoparticles sandwiched between carbon membrane and TiO₂ nanotube arrays (C/Au/TiO₂ NTAF). The two structures exhibited enhanced visible light harvesting ability, but they showed distinctly different photoelectric properties. The unique microstructure of C/Au/TiO₂ NTAF resulted in a much higher reduction of the electron cloud density of Au nanoparticles as carrier recombination centers, which were responsible for its poor photoelectrochemical performance. However, a champion photocurrent of Au/C/TiO₂ NTAF was observed (0.984 mA cm^-2), indicating superior ability of the photoelectrocatalytic water splitting. The great enhancement was attributed to multiple carriers transport paths, which can efficiently utilize the sensitization of the carbon membrane and the surface plasmon resonance effect of the Au nanoparticles.