Acid Corrosion Research Articles

Low LUMO energy carbon molecular interface to suppress electrolyte decomposition for fast charging natural graphite anode

Graphite holds great potential as a next-generation anode material for energy storage devices. However, the low working voltage of graphite leads to electrolyte decomposition, generating harmful byproducts like HF, while its anisotropic structure results in poor Li+ transport kinetics, making it challenging to balance battery stability and fast-charging performance. Herein, a controllable and scalable carbon molecular layer with low-LUMO (lowest unoccupied molecular orbital)energy is successfully designed to alter charge transfer at the electrode surface. The low LUMO energy carbon molecular interlayer between the graphite and solid electrolyte interphase (SEI) contains numerous strong electron-withdrawing and polar functional groups (C-F and C-N). The functional groups in the interlayer can preferentially and rapidly convert into a LiF and Li3N-rich SEI, attributed to their lower reaction energy barrier compared to electrolyte decomposition. Importantly, the electronic effects and intramolecular synergistic effects between polar functional groups make the conversion of C-F to LiF easier. The interayer superior properties that prevent SEI acid corrosion, accelerates the Li+ desolvation and diffusion in the SEI. Therefore, the graphite anode achieves a balance between fast charging and stability, retaining 64.28 % capacity retention after 1000 cycles at 10 A g−1. Additionally, the graphite anode can be applied in potassium-ion batteries, achieving 148.3 mAh g−1 at 0.2 A g−1. This simple and effective interfacial molecular design offers new insights for simultaneously regulating SEI and suppress electrolyte decomposition.

Imidazole derivative for corrosion protection: A comprehensive theoretical and experimental study on mild steel in acidic environments

The inhibition efficiency derivative imidazole, 2-mercapto-5,5-diphenyl-3,5-dihydro-4 H-imidazol-4-one (AM0), against corrosion in a hydrochloric acid (HCl) environment was studied. The research focused on the compound's ability to adsorb onto mild steel surfaces. Various experimental techniques, including potentiodynamic polarization (PDP), electrochemical frequency modulation (EFM), and impedance spectroscopy (EIS), were employed to analyze the inhibitory effects. Results showed that the effectiveness of AM0 increased with concentration, reaching an inhibitory efficiency of 95.1 %. Polarization studies revealed that the inhibitor displayed mixed-type behavior. The adsorption process was modeled using the Langmuir adsorption model. Surface characterization techniques such as scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDS), and X-ray photoelectron spectroscopy (XPS) were utilized to examine the inhibited corrosion surfaces. Theoretical calculations based on density functional theory (DFT) and density functional tight binding (DFTB) suggested that inhibitors with electron-accepting capabilities exhibited strong interactions with the iron surface, shedding light on specific bond formations that contribute to the stability and interaction dynamics at the molecular interface. This study provides valuable information on the corrosion inhibition potential of the new imidazole compound, offering important pointers for the development of effective corrosion inhibitors in acidic environments.

Preparation of superhydrophobic/oleophobic wood coating with fluorinated silica sol by a simple spraying method

The biomimetic construction of superhydrophobic coatings on wood surfaces significantly reduces the water absorption capacity of wood while enhancing its deformation resistance, thereby extending the service life of wooden structures. In this work, a fluorinated silica sol was prepared from alkaline silica sol and 1H,1H,2H,2H-perfluorodecyltrimethoxysilane (PFDMS), and evenly sprayed over the wood surface to effectively produce superhydrophobic/oleophobic wood specimens. The effect of the preparation procedure of fluorinated silica sol on the wettability of the coating was investigated. Acid and alkali corrosion tests were conducted to assess the chemical stability of the superhydrophobic coating, while sandpaper abrasion tests were used to evaluate its mechanical stability. The results showed that with a volume ratio of silica sol to PFDMS of 6:1 and a reaction period of 30 min, the modified wood exhibited excellent superhydrophobicity, with a water contact angle of 157.3° and an oil contact angle of 126.5°. Furthermore, the superhydrophobic coating demonstrated excellent mechanical and chemical durability, along with self-cleaning properties. These findings have significant practical implications for enhancing the performance and longevity of wood.

Hydrogen spillover on Ni@Graphene enables robust and efficient catalytic hydrogenation of aqueous levulinic acid to γ-valerolactone

Hydrogenation of biomass-derived aqueous levulinic acid (LA) to produce γ-valerolactone (GVL) is a promising approach from biomass to sustainable platform chemicals. However, the practical application of this method is limited because aqueous LA is highly corrosive to metal-based hydrogenation catalyst in high-temperature hydrothermal environments. Herein, we encapsulated metallic Ni0 particles with a few layers of graphene using a hydrothermal carbon coating method to obtain Ni@FLG-600 catalyst, which exhibited efficient catalytic activity and excellent cycling stability for the hydrogenation of aqueous LA to GVL. The defect-rich graphene shell prevents the Ni0 from acid corrosion meanwhile selectively permits the passage of small H2 molecules. The resulted active H* on Ni0 spills over to the outer surface of graphene shell and reacts with LA. Remarkably, the amount of H* on graphene shell can be the descriptor of activity. This finding presents a new strategy for the fabrication of acid-resistant catalysts for aqueous biomass hydrogenation.

Preparation and performance study of silicon modified polyurethane-based magnetorheological elastomeric polishing pad

Abstract By employing Magnetorheological Elastomers (MREs) as polishing pads for chemical mechanical polishing (CMP), the magnetorheological properties are utilized to effectively control the flexible removal of materials in CMP. This study presents a method for preparing a Silicon modified Polyurethane (SPU)-based MRE polishing pad, aimed at demonstrating improved magnetorheological properties while preserving mechanical properties. The SPU-based MRE polishing pad was synthesized through the copolymerization of hydroxypropyl silicone oil and polyurethane prepolymers, with subsequent evaluation of its mechanical properties and polishing performance. Fourier Transform Infrared (FTIR) analysis confirmed the successful incorporation of the soft polydimethylsiloxane main chain from organosilicon into the polyurethane main chain, forming a soft segment that intertwines with the polyurethane main chain to create a soft-hard segment crosslinked structure. Comparison to Polyurethane (PU)-based MRE, SPU exhibits significantly reduced hardness but improved wear resistance, as well as enhanced resistance to acid and alkali corrosion. Due to the presence of a soft matrix, SPU shows better magnetorheological effects than PU-based MRE. Under a magnetic field intensity of 845 mT, the magnetorheological effect of PU-based MRE is only 18%, while Si-15.96 and Si-16.79 SPU-based MREs can reach 84% and 110%, respectively. Although the Material Removal Rate (MRR) of single-crystal SiC decreases after polishing with SPU compared to PU-based MRE, a higher surface quality is achieved, and the glazing degree of the polishing pad is significantly reduced. In the magnetic field-assisted polishing of single crystal SiC, the MRR increased by 38.4% when polished with an SPU-based MRE polishing pad, whereas the MRR was only 8.7% when polished with a PU-based MRE polishing pad. This study provides further evidence for the development and application of MRE in CMP.

Enhancing acid corrosion resistance in alkaline-activated materials with water treatment residue and blast-furnace slag

This study investigates the acid corrosion resistance of an alkaline-activated material (AAM) composed of ground granulated blast-furnace slag (GGBFS) and water treatment residue (WTR) as precursors. WTR, a byproduct of the drinking water treatment process rich in aluminium and silicon, proves to be a suitable precursor for AAM after cost-effective pre-treatment involving calcination and grinding. As its low-Ca content and aluminosilicate nature of the treated WTR, the AAM incorporating WTR exhibits significant potential for improving acid resistance. This is attributed to the formation of less acid-reactive N-A-S-H gels than C-A-S-H gels in high-Ca AAMs, indicating its applicability in concrete sewage pipes where microbiologically generated acid corrosion is prevalent. In the paper, a comprehensive analysis, including mechanical performance, ion leaching behaviour, and microstructural characteristics, was conducted on mortar samples containing varying WTR/GGBFS ratios before and after exposure to sulfuric acid. Incorporating WTR up to 40 % effectively reduced acid-induced strength loss compared to neat-GGBFS AAM. The obtained results reveal that high-Ca AAMs facilitate gypsum formation during acid attack, leading to mechanical degradation. The inclusion of WTR induces a Si-rich transition layer between the corroded and intact matrix, mitigating sulfate diffusion. The release of aluminium from WTR promotes secondary precipitation of aluminosilicate, beneficially increasing the thickness of the transition layer. This thicker transition layer in the higher WTR samples is advantageous in reducing the likelihood of cracks and reducing the sulfate transportation into the intact matrix.

Machine learning models and computational simulation techniques for prediction of anti-corrosion properties of novel benzimidazole derivatives

The present paper delves into the development of predictive models for the optimum prediction of inhibition efficiencies and anti-corrosion properties of newly designed benzimidazole compounds in an HCl medium. Density functional theory (DFT) was used to obtain the molecular descriptors. 17 descriptors considered as input variables were reduced to 9 after redundant variables were eliminated using the variance inflation factor (VIF). Machine learning models such as random forest regression (Rf), K-nearest neighbor (KNN), and gradient boosting (GB) were used to develop a predictive model using data from 50 benzimidazole derivatives whose inhibition efficiencies for steel alloy in HCl medium have been determined experimentally and are available in the literature. The cross-validation (CV) technique was used to evaluate the predictive capability of the models. KNN gave the best result with a coefficient of correlation (R2) of 0.654, compared to GB (0.591) and RF (0.512). Subsequently, the three models were used to predict the inhibition efficiencies of three novel benzimidazole compounds. The corrosion inhibition efficiency of three newly developed benzimidazole compounds was 91 % - 98.5 % when assessed with the best-performing model, K-nearest neighbor (KNN) with MSBAH recording the highest value of 98.5 %. Fukui indices parameters fk+k,fk−k,andf2(r) showed that both the electrophilic and nucleophilic sites are concentrated around specific atoms most of whom are heteroatoms that participate actively in electron-donor and acceptor interaction with the metal atom leading to the formation of coordinate covalent bonds. The results of electron distribution and Fukui dual descriptors support the results of the predictive model. The study also revealed that machine learning algorithms in conjunction with DFT and MD simulation is an innovative technique for the prediction of anti-corrosion properties of newly designed molecules such as corrosion inhibition efficiencies, and mechanism of inhibitor adsorption on metal/alloy surfaces exposed to an aggressive environment. This technique can be harnessed in proffering solutions to acid corrosion especially those that occur during descaling operation.

An acid-tolerant metal-organic framework for industrial CO2 electrolysis using a proton exchange membrane

Industrial CO2 electrolysis via electrochemical CO2 reduction has achieved progress in alkaline solutions, while the same reaction in acidic solution remains challenging because of severe hydrogen evolution side reactions, acid corrosion, and low target product selectivity. Herein, an industrial acidic CO2 electrolysis to pure HCOOH system is realized in a proton-exchange-membrane electrolyzer using an acid-tolerant Bi-based metal-organic framework guided by a Pourbaix diagram. Significantly, the Faradaic efficiency of HCOOH synthesis reaches 95.10% at a large current density of 400 mA/cm2 with a high CO2 single-pass conversion efficiency of 64.91%. Moreover, the proton-exchange-membrane device also achieves an industrial-level current density of 250 mA/cm2 under a relatively low voltage of 3.5 V for up to 100 h with a Faradaic efficiency of 93.5% for HCOOH production, which corresponds to an energy consumption of 200.65 kWh/kmol, production rate of 12.1 mmol/m2/s, and an energy conversion efficiency of 38.2%. These results will greatly aid the contemporary research moving toward commercial implementation and success of CO2 electrolysis technology.

True-triaxial strength characteristics of cement stone subjected to sulfuric acid corrosion: An experimental and theoretical study

True triaxial tests were conducted to investigate the effect of sulfuric acid corrosion on the true triaxial strength of cement stone under different acid immersion times, including the common loading path and novel loading path with constant Lode angle. The chemical composition and microstructure of cement stone under different acid immersion times (0, 7, 14, and 28 d) were examined via X-ray diffraction and scanning electron microscopy. As the duration of acid immersion increases, the concentrations of portlandite (Ca(OH)2) and calcium silicate hydrate (C-S-H) within the cement stone exhibit a gradual decline, while the presence of calcium sulfate (CaSO4) progressively rises. The microstructure of the cement stone was primarily affected by two factors: the damaging and strengthening effects of sulfuric acid and CaSO4, respectively. The damaging effects of the acid were dominant for days 0–14 of immersion, with continuous increase in microstructure damage. Subsequently, the strengthening effect of CaSO4 became apparent for days 14–28 of immersion, with continuous improvement in microstructure integrity. Consequently, the strength of cement stone exhibited a diminishing trend during the initial immersion period of 0–14 days, followed by an enhancement in strength from 14 to 28 days of immersion. Furthermore, a three-dimensional strength criterion was proposed by combining the Hoek–Brown and Matsuoka–Nakai criteria. The failure envelope first shrank and then expanded with increasing immersion time, accurately describing the variation in strength in the three-dimensional principal stress space.

Upcycling of High‐Rate Ni‐Rich Cathodes through Intrinsic Structural Features

AbstractThe paradigm shift toward the closed‐loop recycling of spent lithium‐ion batteries necessitates the direct, efficient cathode recovery that goes beyond the traditional pyrometallurgy and hydrometallurgy techniques, meanwhile avoiding substantial energy consumption, tedious procedures, or chemical contamination. In this study, a straightforward, dual‐functional upcycling approach is presented for the spent nickel‐rich cathodes to boost their high‐rate performance. Specifically, the protocol rationally employs the Li vacancy within the degraded oxide to minimize the La diffusion barrier, expanding the lattice spacing of the layered structure; the Li+ conductive, conformal LiLaO2 encapsulation further suppresses the interfacial acid corrosion and structural deterioration into the rock‐salt phase. Transmission‐mode X‐ray diffraction tracks the reversible lattice breathing of the regenerated cathode in operando, suggesting the continuous, kinetically boosted solid‐solution process with all the microcracks repaired. The as‐assembled regenerated LiNi0.8Co0.1Mn0.1O2/Graphite pouch cell (1.4Ah) thus achieves 91.0% capacity retention for 500 cycles, the energy density of 277 Wh kg−1 as well as extreme power output of 1030 W kg−1 at the cell level. This upcycling strategy paves the way for value‐added utilization of the retired Ni‐rich cathodes in practical high‐rate battery prototypes.

Biomass of Anthonotha macrophylla leaf extract as a mild steel acid corrosion inhibitor: Experimental and theoretical study

This study investigated weight loss and electrochemical impedance spectroscopy (EIS) to explore the inhibition potential of Anthonotha macrophylla leaf extract (AME) on mild steel corrosion in 0.5 M H2SO4 medium. The result shows that the highest inhibition efficiency of 90.47 % at 303 K and 80.02 % at 333 K were obtained. At temperatures of 303 K and 333 K, it was discovered that the corrosion rate decreased as the concentration of the AME inhibitor rose from 0.1 g/L (7.73×10−4gcm−2hr−1) to 0.5 g/L (2.27×10−4 gcm−2hr−1). The result of the EIS measurement is in consistent with that of the weight loss method. Adsorption isotherms portrayed that Tempkin and Freundlich's adsorption isotherms were obeyed. Calculated values of Ea, ∆Hads and ∆Gads suggested a physical adsorption mechanism. FTIR, SEM-EDX, and XRD measurements revealed that the AME inhibitor efficiently shields the mild steel surface from further corrosion attack by inducing the formation of passivated film on the mild steel surface. The calculated quantum parameters correlated with experimental results, thus, AME can be used as an alternative inhibitor for the protection of mild steel against corrosion.

Investigation of safe operating conditions for reducing acid corrosion and ABS deposition in rotary air preheater using computational fluid dynamics

Investigation of safe operating conditions for reducing acid corrosion and ABS deposition in rotary air preheater using computational fluid dynamics

Challenges and Opportunities in Preparing Fe-N-C Layers Supported on Non-Carbon Supports

Global energy demand will be continuously rising in the foreseeable future. To mitigate the results of climate change it is necessary to reduce the emittance of greenhouse gases. One promising approach is to switch to hydrogen as energy carrier and use proton exchange membrane fuel cells (PEMFCs) to efficiently convert H2 into electric power. Here, hydrogen and oxygen/air are used to directly generate electrical energy with only water as byproduct. Both reactions need to happen efficiently at the same time. The oxygen reduction reaction (ORR), however, is a very sluggish four-electron-reaction and needs efficient catalysts.The state-of-the-art ORR catalyst in PEMFC is platinum but that is a very scarce and expensive metal. Hence, it is important to switch to precious-metal-group (PGM) free catalysts. In recent years, bio inspired iron-based FeNC catalysts have been shown to approach ORR activities that are competitive with those of platinum, even though they need a higher catalyst loading than Pt to reach the desired high current densities.1–3 Those catalysts feature single Fe atoms surrounded by four N atoms in graphitic carbon. The drawback of those materials is their lower stability compared to PGM materials. In a nutshell, the carbon matrix oxidizes during operation in PEMFCs, changing the morphology of the catalytic center and rendering it less active, or inactive, depending on the carbon oxidation extent. Direct demetallation phenomena are also possible, leaving a N4 cavity without metal cation center. It was shown recently by Wu et al.4 that it is possible to raise durability by adding an additional carbon layer on the catalyst. One alternative approach to reduce those degradations is to interface Fe-N4 sites with a carbon-free support. The targeted support material must be immune to corrosion in acid and withstand the typical ORR electrochemical potentials. It also has to be electrically conductive to facilitate electron transfers, both locally and on long scale.In this work, conductive ceramic metal oxide materials (Ta doped SnO2, TTO) was investigated as a possible alternative catalyst supports. This material is resistant to acid and can withstand prolonged potentials at operating conditions in PEMFCs.5 During the synthesis of the FeNC catalysts, high temperatures are generally applied. Such treatments can be detrimental to the conductivity of ceramics due to metal aggregation (in case of doped materials) and may also lead to morphological changes as well as the reduction of the ceramics to metallic materials. A robust method to synthesize FeNC catalysts is by mixing the separate Fe, N and C precursors and using optimized thermal treatment. In this study, the effect of the pyrolysis conditions as well as the ratio of FeNC precursors to TTO was investigated with various characterization methods, e.g. X-ray absorption spectroscopy, Mossbauer spectroscopy, and high resolution TEM. The characterization techniques confirm the presence of single atom Fe as well as different Sn species that might contribute to the activity. The resulting materials were electrochemically characterized with rotating disc electrode techniques and in PEM fuel cells for their ORR-activity and durability. It was shown that the activity of materials with a high FeNC precursor content relative to TTO can outperform a reference FeNC synthesized similarly but without TTO, in both RDE (Figure) and PEMFC.The presentation will report in detail the effects of pyrolysis conditions and FeNC precursor/TTO content on the structure, activity and stability of materials.(1) Mehmood, A. et al. High Loading of Single Atomic Iron Sites in Fe–NC Oxygen Reduction Catalysts for Proton Exchange Membrane Fuel Cells. Nat. Catal. 2022, 5 (4), 311–323. https://doi.org/10.1038/s41929-022-00772-9.(2) Gasteiger, H. A.; Marković, N. M. Just a Dream—or Future Reality? Science 2009, 324 (5923), 48–49. https://doi.org/10.1126/science.1172083.(3) Zion, N. et al.. Electrocatalysis of Oxygen Reduction Reaction in a Polymer Electrolyte Fuel Cell with a Covalent Framework of Iron Phthalocyanine Aerogel. ACS Appl. Energy Mater. 2022, 5 (7), 7997–8003. https://doi.org/10.1021/acsaem.2c00375.(4) Liu, S.et al. Atomically Dispersed Iron Sites with a Nitrogen–Carbon Coating as Highly Active and Durable Oxygen Reduction Catalysts for Fuel Cells. Nat. Energy 2022, 7 (7), 652–663. https://doi.org/10.1038/s41560-022-01062-1.(5) Jiménez-Morales, et al. Strong Interaction between Platinum Nanoparticles and Tantalum-Doped Tin Oxide Nanofibers and Its Activation and Stabilization Effects for Oxygen Reduction Reaction. ACS Catal. 2020, 10 (18), 10399–10411. https://doi.org/10.1021/acscatal.0c02220. Figure 1

PGM-Free Oxygen Evolution Reaction Catalyst for PEM Water Electrolysis – a Mechanistic Study on Activity and Durability for Practical Applications

Low temperature proton exchange membrane water electrolyzer (PEMWE) represents a critical technology for green hydrogen production. It offers the advantages of significantly higher current density and higher H2 purity, rendering it a preferred technology when high energy efficiency and low footprint are essential. Working in the oxidative and acidic environment under high polarization voltage, however, adds substantial demand to the electrode catalyst and the support. This is particularly the case at anode where the oxygen evolution reaction (OER) takes place. At present, the platinum group metal (PGM) materials such as Ir black or Ir oxide are catalysts of choice. Their high cost and limited reserve add a significant cost barrier to PEM electrolyzer, which contributes to the overall expense of hydrogen production next only to the cost of electricity. Replacing Ir with earth-abundant transition metal oxides could help to reduce the electrolyzer system cost.For PEMWE application, a PGM-free anodic catalyst must be highly active to match the performance of Ir. Furthermore, it must be stable against oxidative acid corrosion. At Argonne National Laboratory, we recently developed a new PGM-free OER of a nanofibrous cobalt spinel catalyst co-doped with lanthanum and manganese (LMCF). [1] The catalyst was synthesized from the precursor of cobalt zeolitic methyl-imidazolate framework (Co-ZIF) doped with manganese and lanthanum. The Co-ZIF was mixed with a polymer solution and electrospun into nanofiber before being converted to fibrous cobalt spinel under low temperature oxidation to remove all the organics and carbon. The new PGM-free catalyst demonstrated a low overpotential of 353 mV (RHE) at 10 mA/cm2 and a low OER degradation over 360 hours in acidic electrolyte. A PEMWE containing this catalyst at its anode at ~2.0 mg/cm2 demonstrated a current density of 2000 mA/cm2 at 2.47 volts (Nafion® 115 membrane) or 4000 mA/cm2 at 3.00 volt (Nafion® 212 membrane). The membrane electrode was also subjected to accelerated-stress-test (AST) in both voltage cycling and galvanostatic run at different current densities. Low degradation rates under both ASTs were observed.In addition to catalyst design and synthesis, we also conducted extensive structural characterizations, stability measurement, as well as computational modeling. Our in situ study found that the OER process involves significant lattice oxygen movement, leading to lowering instead of raising the cobalt oxidation state during the electrolysis. The measurement of the stability number, combined with computational Pourbaix diagram, elucidated the importance of the operating potential in reducing catalyst dissolution. These findings offer in-depth understanding and direction of future development for PGM-free OER catalyst in PEM water electrolyzer. Acknowledgement: This work is supported by the U.S. Department of Energy, Office of Energy Efficiency and Renewal Energy, Hydrogen and Fuel Cell Technologies Office, and by Laboratory Directed Research and Development funding of Argonne National Laboratory, provided by the Director, Office of Science, of the U.S. Department of Energy under Contract No. DEAC02-06CH11357. Work performed at the Center for Nanoscale Materials and Advanced Photon Source, both U.S. Department of Energy Office of Science User Facilities, was supported by the U.S. DOE, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.[1] “La- and Mn-doped cobalt spinel oxygen evolution catalyst for proton exchange membrane electrolysis” Lina Chong, Guoping Gao, Jianguo Wen, Haixia Li, Haiping Xu, Zach Green, Joshua D. Sugar, A. Jeremy Kropf, Wenqian Xu, Xiao-Min Lin, Hui Xu, Lin-Wang Wang, Di-Jia Liu, Science 380, 609–616 (2023)

Silicalite‐1 encapsulated Cu‐based catalyst for selective hydrogenation of maleic anhydride to γ‐Butyrolactone

γ‐Butyrolactone (GBL) is an important product of the hydrogenation reaction of maleic anhydride (MA). In this study, Cu@Silicalite‐1 (Cu@S1) catalyst with 20% Cu loading was synthesized using a combination of impregnation & solid‐phase synthesis. The effect of Cu and Silicalite‐1 zeolite binding methods on the MA hydrogenation was investigated methodically. MA conversion reached 96.2% and GBL selectivity reached 27.6% at 240 °C, with maintained catalytic activity after propionic acid corrosion for 150 h on the Cu@S1 catalyst. S1 zeolite as a critical factor for significant effect on MA selective hydrogenation raction over Cu‐based catalysts, it was conducive to improving GBL selectivity and reducing the generation of propionic acid (PA) by‐products. The encapsulation of Cu particles by S1 zeolite promoted metal dispersion, increased the hydrogenation activity and promoted the adsorption of reactants, which provided a reference for improving the acid and water resistance of the catalysts

Study on mechanical properties and damage characteristics of acid corrosion in granite based on NMR technology

In acidic environments, rock masses are frequently subjected to severe chemical corrosion, resulting in the initiation of numerous geological engineering disasters. This study aimed to collect physical and mechanical parameters of granite exposed to prolonged acid corrosion and analyze fracture characteristics using acoustic emission (AE) techniques. Additionally, it examined the evolution of pore structure and damage mechanisms through the use of low-field nuclear magnetic resonance (NMR) and fractal theory. The results demonstrate a monotonic decrease in mass, volume, density, P-wave velocity, and S-wave velocity of granite with increasing corrosion time. Particularly notable is the phased reduction observed in uniaxial compressive strength and elastic modulus. The transition from brittle to ductile failure in corroded granite is accompanied by a gradual decrease in internal fracture strength. The trend in the correlation dimension reveals the relationship between the formation time of the main fracture surface and the pore structure. Additionally, total porosity and macropores (D, Da) exhibit significant fractal characteristics. The fractal dimension correlates positively with the damage variable and inversely with uniaxial compressive strength and elastic modulus. This indicates that more severe pore structure damage leads to a higher fractal dimension and lower mechanical performance. Among these, Da demonstrates higher sensitivity in characterizing rock mechanical properties. These findings provide important basis for evaluating the stability of granite geotechnical engineering in acidic environments.

Dual Modulation of Bulk Electronic Structure and Surficial Active Sites in Sea Urchin‐Like MoO2 Nanoreactors Promoting Electrocatalytic Hydrogen Evolution

AbstractElectrocatalytic hydrogen evolution reaction (HER) is a promising strategy for realizing carbon neutralization as well as for the production of green hydrogen. Molybdenum dioxide (MoO2), possesses acid corrosion resistance and near‐metal‐level conductivity, endowing its widespread application in acidic HER. However, due to spatial barriers at the edge of sites and weak H* adsorption, the HER activity of MoO2 is greatly limited. Herein, a sea urchin‐like Pt@N‐MoO2 nanoreactor is designed, in which the bulk electronic structure and surface‐active sites are modulated by N doping and Pt single atoms anchoring, respectively. DFT calculations indicate that Mo─N coupling changes the charge density of Mo atoms, enhances the adsorption of H*, and thus optimizes the Gibbs free energy. The appearance of Pt‐O/N sites compensates for the lack of active sites exposed by MoO2, while promoting the desorption of H2 from the catalyst surface and accelerating the HER process. This work provides an effective strategy for activating inert electrocatalysts to promote energy conversion via a dual modulation strategy of bulk and surface engineering.

Dynamic mechanical properties and fractal characteristics of red sandstone under acid corrosion

Dynamic mechanical properties and fractal characteristics of red sandstone under acid corrosion

Deciphering microbial communities involved in marine steel corrosion using high-throughput amplicon sequencing.

To characterize the source and effects of bacterial communities on corrosion of intertidal structures, three different UK coastal sites were sampled for corrosion materials, sediment and seawater. Chemical analyses indicate the activity of sulfate-reducing microbes (SRBs) at 2 sites (Shoreham and Newhaven), but not at the third (Southend-on-Sea). Microbial communities in the deep sediment and corrosion samples are similar. The phylum Proteobacteria is dominant (40.4% of the total ASV), followed by Campilobacterota (11.3%), Desulfobacterota and Firmicutes (4%-5%). At lower taxonomic levels, corrosion causing bacteria, such as Shewanella sp. (6%), Colwellia sp. (7%) and Mariprofundus sp. (1%), are present. At Southend-on-sea, the relative abundance of Campilobacterota is higher compared to the other two sites. The mechanism of action of microorganisms at Shoreham and Newhaven involves biogenic sulfuric acid corrosion of iron by the combined action of SRBs and sulfur-oxidizing microbes. However, at Southend-on-sea, sulfur compounds are not implicated in corrosion, but SRBs and other electroactive microbes may play a role in which cathodic reactions (electrical MIC) and microbial enzymes (chemical MIC) are involved. To contribute to diagnosis of accelerated intertidal corrosion types, we developed a rapid identification method for SRBs using quantitative polymerase chain reaction high-resolution melt curve analysis of the dsrB gene.

Menadione sodium bisulfite as an efficient anti-corrosion additive for mild steel in acid corrosion: Electrochemical, surface morphological and theoretical studies

The corrosion inhibition behavior of Menadione Sodium Bisulfite (MSB) in 1.0 M HCl medium was evaluated using weight loss, electrochemical techniques (Tafel polarisation and Electrochemical impedance spectra), surface analysis (SEM and EDX), Density Functional Theory (DFT), Noncovalent interaction- Reduced Density Gradient (NCI-RDG) and Monte Carlo (MC) simulation techniques. Weight loss measurement showed that as inhibitor concentration increased, the corrosion rate decreased which means that a protective film formed on the metal surface. At 300 ppm, the inhibitor showed a maximum inhibition efficiency of 89.7 %. Tafel polarisation studies indicate that the inhibitor is mixed-type in nature. The inhibitor adsorption on the mild steel is the best fit for the Langmuir isotherm model. As the weak interaction of sodium and oxygen in the inhibitor molecules, the inhibitor exhibits two distinct equilibrium behaviors. (i) inhibitor with sodium (solid-state) and inhibitor without sodium (in liquid-state). These two behaviors were theoretically investigated using DFT and MD simulation studies. The inhibitor and metal interaction is further supported using these theoretical studies. The electron population of the inhibitor was analyzed using molecular electrostatic potential, NCI-RDG, Fukui function, and natural bond orbital analysis. These studies further give an understating of the inhibitor and metal interactions.