[en] With nano-SiO₂ and sulphate acid, a kind of colloid electrolyte is synthesized by sol-gel method. It is placed outside the reference electrode as a layer of gel electrolyte so as to decrease the leaching of Cu²⁺ and increase the life of the reference electrode. The performance of the gel electrode in simulating soil solution is measured as follows: the potential of the electrodes ranging from 60 mV to 80 mV (vs. SCE) with potential variation no more than ±10 mV, enough resistance to polarization. The Cu²⁺ effusion rate of the reference electrode without gel electrolyte is 3 times that with colloid electrolyte, which means that gel electrolyte can extend the life of the reference electrode significantly

[en] Pitting corrosion of high-strength steel 10Ni8CrMoV under square wave polarization (SWP) in simulated deep-sea environment is investigated and the possible mechanism is proposed. The results show that potential perturbation generates periodic intensification effect on both anodic and cathodic processes by frequently breaking the electrode equilibrium state. The intensity of periodic intensification effect essentially depends on the concentration gradient of Fe²⁺ cations at the steel/solution interface which acts as the forced electrochemical oscillator. The concentration gradient and the resulting concentration polarization effect increase periodically with the increase in SWP potential range. The morphology observation of the pitting and electric charge calculation indicate that the periodic intensification effect can promote the initiation and growth of pits by enhancing the anodic dissolution even under cathodic protection, but it is ineffective below the hydrogen evolution potential. The decrease in either upper or lower potential can mitigate anodic dissolution. Through the statistical analysis of pitting size, it is found that the wide potential range tends to activate the metastable pitting formed under hydrostatic pressure, forming densely distributed pitting. Meanwhile, it is more favorable to the formation of fully grown pits with high size dispersion degree when the proportion of electric charge in the anodic process is higher.

[en] For the first time, the corrosion behavior of Q235 steel in 1200, 2000 and 3000 m deepwater of South China Sea for 0.5 year was reported in this study. The corrosion morphology and corrosion products properties were investigated using different techniques, such as 3D optical microscope, scanning electron microscope, x-ray diffraction analyzer and electrochemical impedance spectroscopy. The main environmental factors influencing the corrosion rate of Q235 in deep sea were discussed by applying gray relational analysis. The results indicated that uniform thinning occurred after exposure. A large number of tiny pits were distributed under the corrosion products with a two-layer structure. The corrosion rate and average pitting depth of samples exposed at 2000 m were lower than those exposed at 1200 and 3000 m, and the main environmental factors determining the variation of corrosion rate at different depths were temperature and dissolved oxygen concentration. Hydrostatic pressure had slight effect on the corrosion rate of Q235 steel, but promoted the formation of a more uniform corrosion morphology.

[en] The microstructure and electrochemical behaviors of Mg-Al-Zn and Mg-Al-Zn-Ga alloys as anode materials were investigated by morphology observation, composition analysis, phase identification, and electrochemical tests. The experimental results suggest that Ga alloying can refine the grains of the Mg-Al-Zn alloy by promoting second-phase segregation, which comprises Mg₁₇Al₁₂ and GaMg₂. The comparison of discharge tests indicates that adding Ga to the Mg-Al-Zn alloy can negatively shift the discharge potential, provide a high current density, promote the formation of tiny and thin products, and improve the utilization efficiency. Meanwhile, the addition of Ga can increase the corrosion resistance of Mg-Al-Zn alloy because the Ga alloying promotes the segregation of the intermetallic phases in the Mg matrix. The intermetallic phases disperse in isolate states in the Mg matrix, resulting in their falling off from the substrate once their adjacent Mg is exhausted and subsequently ceasing the micro-galvanic corrosion. The Mg-Al-Zn-Ga alloy with higher corrosion resistance performs better discharge activity than that of Mg-Al-Zn alloy in 3.5 wt.% NaCl solution, implying that the Mg-Al-Zn-Ga alloy is a promising anode material for seawater-activated battery.

[en] The electrodes of IrO₂-Ta₂O₅ coated titanium were prepared using conventionally thermal decomposition procedure and polymer sol-gel (Pechini) method, respectively. The microstructure and electrochemical properties of the electrodes were studied with scanning electron microscope (SEM), energy dispersive X-ray (EDX), atomic force microscope (AFM), potentiodynamic polarization, cyclic voltammetry, electrochemical impedance spectroscopy and accelerated life test. As compared with the electrode formed using the traditional method of thermal decomposition, the oxide electrode prepared by Pechini method presents morphology of higher nano-scale roughness and more uniform surface composition with little precipitates. It also has larger electrochemically active surface area, better electrocatalytic activity for oxygen evolution and higher stability

[en] g-C₃N₄ is a promising material for the application in the area of photoelectrochemical cathodic protection. However, it suffers from limited light absorption and lower charge separation efficiency. In this work, a N defects and C deposition co-modified g-C₃N₄, C–g-C₃N_x, was prepared by NaOH-assisted sintering and ethanol-assisted hydrothermal treatment. The presence of N defects and C deposition was verified by the XRD, SEM and XPS tests. The N defects changed the band structure of g-C₃N₄ by lowering down the conduction band position, therefore widening the light absorption range of g-C₃N₄. In addition, the N defects and C deposition co-modification promotes the charge transfer process of g-C₃N₄, leading to increased separation efficiency of the photogenerated charge carriers. Therefore, C–g-C₃N_x shows enhanced photoelectrochemical cathodic protection performance for the coupled 316L stainless steel. It can provide a photoinduced potential drop of 120 mV and a photoinduced current density of 9.1 μA cm⁻², which is three times that of pristine g-C₃N₄.

[en] The AgInS₂/In₂S₃ nanoparticles (NPs) co-sensitized TiO₂ nanotube array (NTA) photoanodes with high photoelectrochemical (PEC) conversion efficiency are prepared and optimized. The In₂S₃ buffer layer around AgInS₂ absorber layer significantly improves the charge generation/separation efficiency of the prepared photoanode. Compared with single AgInS₂ NPs sensitized TiO₂ NTAs, the design of the AgInS₂/In₂S₃ heterojunction NPs sensitized TiO₂ NTAs further promotes the charge transfer in the system, and avoids the unmatched energy band alignment between AgInS₂ and TiO₂. The AgInS₂(3)/In₂S₃(5) NPs co-sensitized TiO₂ NTAs possess the best PEC conversion performance. The AgInS₂ and In₂S₃ NPs distribute uniformly on TiO₂ NTAs to form close interfacial adhesion. Simultaneously, the one-dimensional TiO₂ nanotubes serve as the direct electron pathways and ensure the rapid collection of charge carriers generated by the system. Moreover, due to the more negative Fermi levels and energy band potentials of AgInS₂ and In₂S₃, the prepared TiO₂ NTA/AgInS₂(3)/In₂S₃(5) photoanode also exhibits an excellent PEC cathodic protection performance for 316L stainless steel in NaCl solution.

[en] Highlights: • Single element-doped ZnO was investigated by DFT calculation. • The single-doping elements could shorten the band gap of ZnO. • The impurity states near the Fermi level can be induced by Fe, Cu, B and N doping. • The p-type doping and intrinsic doping was proposed to improve the photocatalytic properties. -- Abstract: In the present paper, the electronic structure and the optical properties of metallic and nonmetallic elements-doped ZnO were investigated based on the principle of photocatalysis by first-principle density functional theory. Element doping shortens the band gap of ZnO. Due to the p-type characteristics, Fe, Cu, B and N doping brings impurity states over the Fermi level of ZnO, resulting in the shortening of the band gap, extending the absorption and utilization of solar light and thus enhancing the photocatalytic properties of ZnO. However, no impurity states appear in the band gap of Cd- and S-doped ZnO due to the intrinsic doping of Cd and S. Further investigations indicate that different doping atoms can indeed alter the near-Fermi level density of states (DOS) of ZnO and their electronic structures via substitution of zinc and oxygen atoms. In addition, the optical properties of ZnO are improved after doped with different atoms by comparing with those of pure ZnO. Due to the difference of their outer shell electrons of the doped atoms, the optical absorption properties of the investigated materials are followed as the following order: Fe-/B-doped ZnO > Cu-/N-doped ZnO > Cd-/S-doped ZnO > pure ZnO.

[en] An ultrathin 2D/2D C₃N₄/MoS₂ (U-CN/MoS₂) heterojunction photocatalyst was prepared by a simple mechanical grinding technique to investigate the photocatalytic degradation RhB and hydrogen production performance. Physical characterization shows that the ultrathin MoS₂ nanosheets (U-MoS₂) can form heterojunction with the ultrathin C₃N₄ (U-CN), and their intrinsic crystal structure remains stable. Further photocatalytic performance test demonstrated that the U-CN/MoS₂ heterojunction photocatalyst significantly enhanced the photocatalytic activity of U-CN. The U-CN/MoS₂ photocatalyst with 3% mass fraction of MoS₂ station (U-CN/MoS₂-3) has the optimal photocatalytic performance. Due to MoS₂ has a suitable band structure and can replace noble metal as a co-catalyst, the U-CN/MoS₂-3 could achieve the hydrogen production efficiency of 385.04 μmol∙h⁻¹∙g⁻¹, which makes MoS₂ show potential in photocatalytic hydrogen production. The enhanced photocatalytic performance was attributed to the significantly enhanced concentration of photogenerated carriers, the effective separation of photogenerated carriers, and suppressed recombination of photogenerated electrons and holes in the photocatalytic reaction.

[en] Highlights: • Passivity degradation of UNS N08800 in thiosulphate solution is investigated. • Thiosulphate can be reduced on a passive surface. • Elemental sulphur particles are found on the passive film. • Pitting potentials evolve substantially due to competitive adsorption of thiosulphate and chloride ions. • Sulphur ions can incorporate into the outer layer of the passive film. - Abstract: Reduced sulphur induced corrosion of steam generator (SG) tubing in pressurized water reactor (PWR) is assumed to occur at low temperature. Corrosion of UNS N08800 in chloride and thiosulphate solutions at 20, 40 and 90 $\mathrm{℃}$ is systemically investigated by using polarization technique, electrochemical impedance spectroscopy (EIS), and X-ray photoelectron spectroscopy (XPS). It is concluded that thiosulphate can be reduced to S°, S₂²⁻ and S²⁻, and incorporate into the passive film, which significantly depends on temperature. The evolution on pitting potentials in chloride + thiosulphate solution can be ascribed to the competitive adsorption of these two ions on the passive surface.