Anti-corrosion performance of the mild steel substrate treated by a novel nanostructure europium oxide-based conversion coating: Electrochemical and surface studies

Surface adsorption and corrosion resistance performance of modified chitosan: Gravimetric, electrochemical, and computational studies

Two novel chitosan derivatives (water soluble and acid soluble) modified with thiocarbohydrazide were produced by a quick and easy technique using formaldehyde as links. The novel compounds were synthesized and then characterized by thermogravimetric analysis, elemental analysis, nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, and differential scanning calorimetry. Their surface morphologies were examined using scanning electron microscopy. These chitosan derivatives could produce pH-dependent gels. The behavior of mild steel in 5 % acetic acid, including both inhibitors at various concentrations, was investigated using gravimetric and electrochemical experiments. According to the early findings, both compounds (TCFACN and TCFWCN) functioned as mixed-type metal corrosion inhibitors. Both inhibitors showed their best corrosion inhibition efficiency at 80 mg L-1. TCFACN and TCFWCN, showed approximately 92 % and 94 % corrosion inhibition, respectively, at an optimal concentration of 80 mg L-1, according to electrochemical analysis. In the corrosion test, the water contact angle of the polished MS sample at 87.90 °C was reduced to 51 °C. The water contact angles for MS inhibited by TCFACN and TCFWCN in the same electrolyte were greater, measuring 78.10 °C and 93.10 °C, respectively. The theoretical results also support the experimental findings.

Computational molecular-level prediction of heterocyclic compound-metal surface interfacial behavior

It is difficult to comprehensively understand the interfacial mechanism (IM) of the adsorption of corrosion inhibitors (CIs) on metal surfaces solely through experiments and electronic structure parameters of isolated molecules. To better understand the molecular-level IM of CIs, a combination of atomistic simulations and first-principles calculations was used to obtain reliable information on the adsorption nature and intermolecular interactions during the actual interfacial behavior. The IM and property changes of two synthesized heterocyclic sustainable-green CIs, namely 4-{[(5-nitrofuran-2-yl)methylene]amino}-5-propyl-4H-1,2,4-triazole-3-thiol (NFPT and 4-{[(5-nitrofuran-2-yl)methylene]amino}-4H-1,2,4-triazole-3-thiol (NFT), were investigated on the Fe(110) surface using first-principles density functional theory (DFT) calculations and molecular dynamics (MD) simulations. The NFPT was preferentially adsorbed through a parallel configuration with a high interaction energy (-706.12 kJ·mol^-1) compared to NFT, owing to stronger chemical bonds via S, N, and O atoms with the Fe surface. Additionally, the adsorbed NFPT film effectively inhibited Fe surface corrosion owing to the small diffusion coefficient of corrosive particles in the presence of NFPT. Subsequently, the anti-corrosion performance of both CIs was validated through electrochemical methods, surface analysis, and adsorption isotherm models. The observations suggest that the combination of modern computational perspectives could efficiently design and select the best CIs before their laboratory synthesis.

Metal-organic frameworks/ hydrotalcite/graphene oxide sandwich composites derived Fe-Ce@GSL hierarchical materials as highly efficient catalysts for rechargeable Zn-air batteries

The fabrication of efficient bi-functional catalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) applied in energy storage and conversion devices like Zn-air batteries to solve the growing energy and environmental crises has attracted great attentions. In this work, the Fe-Ce@GSL catalysts have developed by first constructing the MOF/LDH/GO templates with multi-stage mixed growth method followed by calcining the template at high temperature. Fe-Ni-LDH (hydrotalcite) plays the role of linking the metal organic frameworks (Fe-Ce-MOF) and graphene oxides (GO), avoiding the separation of MOFs derivatives and GO sheets during pyrolysis process. Rare-earth metal oxide (CeO₂) featuring with abundant oxygen vacancies dispersed on the surface of transition-metal oxide can efficiently improve the stability of catalysts. The optimal Fe₇-Ce₁@GSL-800 catalysts exhibit excellent ORR/OER performances with the potential gap between ORR (E_1/2 = 0.87 V) and OER (E_J=10 = 1.59 V) of 0.720 V. The aqueous Zn-air battery assembled with Fe₇-Ce₁@GSL-800 catalysts exhibits outstanding performances with high open circuit voltage (1.56 V), large specific capacity (801.1 mAh/g@10 mA.cm^-2), and good charge-discharge cycle performances (>500 h). The Fe₇-Ce₁@GSL-800 based solid-state Zn-air battery also delivers an excellent performance with high specific capacity (791.7 mAh/g@5 mA.cm^-2) and long cycle stability (>230 h).