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Graphene (Gr) is a promising material for addressing microbially induced corrosion (MIC) issues that cause staggering economic losses, estimated at nearly $55 billion annually in the US alone. However, structural defects including edges, grain boundaries, and cracks can compromise its performance in aggressive biological environments. Owing to the technological relevance of nickel (Ni), its key roles in biological mechanisms, and the strong hybridization of d-electrons of Ni with Gr π-orbitals, we explore the effects of the key defects in Gr/Ni exposed to archetype sulfate-reducing bacteria (SRB). Electrochemical and spectroscopy tests revealed that the grain boundaries play a stronger role than cracks. The edges and grain boundaries in as-grown Gr on Ni (dGr/Ni) aggravated corrosion by two-fold, while the cracks in the transferred counterpart that lacked these defects improved corrosion resistance by 2-fold. A combination of biotic and abiotic studies corroborated the unique roles of grain boundaries as sulfur reservoirs to promote the attachment of sessile SRB cells and subsequent redox reactions. Analysis of distinct biogenic products confirmed the role of grain boundaries on pitting corrosion. These insights can guide the rational design of graphene coatings specifically for biological environments prone to MIC.

Dehydrogenation of methanol (CH 3 OH) into direct current (DC) in fuel cells can be a potential energy conversion technology. However, their development is currently hampered by the high cost of electrocatalysts based on platinum and palladium, slow kinetics, the formation of carbon monoxide intermediates, and the requirement for high temperatures. Here, we report the use of graphene layers (GL) for generating DC electricity from microbially driven methanol dehydrogenation on underlying copper (Cu) surfaces. Genetically tractable Rhodobacter sphaeroides 2.4.1 (Rsp), a nonarchetypical methylotroph, was used for dehydrogenating methanol at the GL-Cu surfaces. We use electrochemical methods, microscopy, and spectroscopy methods to assess the effects of GL on methanol dehydrogenation by Rsp cells. The GL-Cu offers a 5-fold higher power density and 4-fold higher current density compared to bare Cu. The GL lowers charge transfer resistance to methanol dehydrogenation by 4 orders of magnitude by mitigating issues related to pitting corrosion of underlying Cu surfaces. The presented approach for catalyst-free methanol dehydrogenation on copper electrodes can improve the overall sustainability of fuel cell technologies.

Photosynthetic microbial fuel cells (pMFC) represent a promising approach for treating methanol (CH 3 OH) wastewater. However, their use is constrained by a lack of knowledge on the extracellular electron transfer capabilities of photosynthetic methylotrophs, especially when coupled with metal electrodes. This study assessed the CH 3 OH oxidation capabilities of Rhodobacter sphaeroides 2.4.1 in two-compartment pMFCs. A 3D nickel (Ni) foam modified with plasma-grown graphene (Gr) was used as an anode, nitrate mineral salts media (NMS) supplemented with 0.1% CH 3 OH as anolyte, carbon brush as cathode, and 50 mM ferricyanide as catholyte. Two simultaneous pMFCs that used bare Ni foam and carbon felt served as controls. The Ni/Gr electrode registered a two-fold lower charge transfer resistance (0.005 kΩ cm 2 ) and correspondingly 16-fold higher power density (141 mW/m 2 ) compared to controls. The underlying reasons for the enhanced performance of R. sphaeroides at the graphene interface were discerned. The real-time polymerase chain reaction (PCR) analysis revealed the upregulation of cytochrome c oxidase, aa3 type, subunit I gene, and Flp pilus assembly protein genes in the sessile cells compared to their planktonic counterparts. The key EET pathways used for sustaining CH 3 OH oxidation were discussed., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Experimental data from fixed-bed column studies and a numerical model based on convection-dispersion equations were used to describe transport and retention of Graphene Oxide (GO) in sand, biochar (BC), and BC modified with nanoscale zero-valent iron (BC-nZVI). Three blocking functions, namely no blocking, site-blocking, and depth-dependent blocking, were used to analyze GO transport and retention behavior in each media as a function of Ionic Strength (IS). An inverse modeling approach was implemented to determine the attachment coefficient (K a ) and maximum solid-phase retention capacity (S max ). The Langmuirian attachment model with site-blocking function effectively described experimental GO breakthrough curves (R 2  ~ 0.70-0.99) compared to other models, indicating the importance of introducing a limit on the attachment capacity of the media. The K a values for BC and BC-nZVI were significantly higher than sand, attributable to high porosity, roughness, and surface chemical properties. The models predicted an increasing trend in K a (0.065 to 0.615 min -1 ) in BC with increasing IS (0.1 to 10 mM), while K a values decreased (2.26 to 0.349 min -1 ) for BC-nZVI. A consistent increase in S max was observed for both BC and BC-nZVI with increasing IS. Scenario analysis was conducted to further understand the effect of influent IS, GO concentration, and treatment depth. BC-nZVI exhibited a higher K a and S max and as a result, higher GO retention than BC at lower IS (0.1 and 1.0 mM). BC-nZVI had a relatively lower K a (0.349 min -1 ) at 10 mM IS, however, it outperformed BC when GO retention capacities are compared over a longer period attributable to a higher S max (6.47). Complete GO breakthrough occurred in a 5 cm media after 350 and 465 days for BC and BC-nZVI, respectively at 10 mM IS and influent concentration of 0.1 mg·L -1 . GO breakthrough time increased with increasing treatment depth, however, the relation was non-linear., (Published by Elsevier B.V.)

Modern society envisions hydrogen (H 2 ) fuel to drive the transportation, industrial, and domestic sectors. Here, we explore use of graphene oxide nanoparticles (GO NPs) for greatly enhancing bio-H 2 production by a consortium based on Thermoanaerobacterium thermosaccharolyticum spp. Thermophilic batch bioreactors were set up at 60 O C and initial pH of 8.5 to assess the effects of GO NPs supplements on biohydrogen production. Under optimal GO NPs loading of 10 mg/L, the supplemented system yielded ∼ 300% higher H 2 yield (6.78 mol H 2 /mol sucrose) than control. Such an optimized system offered 73% H 2 purity and 85% conversion efficiency by promoted the desirable acetate fermentation pathway. Miseq Illumina sequencing tests revealed that the optimal levels of GO NPs did not alter the microbial composition of consortium., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Friction-induced energy dissipation impedes the performance of nanomechanical devices. Nevertheless, the application of graphene is known to modulate frictional dissipation by inducing local strain. This work reports on the nanomechanics of graphene conformed on different textured silicon surfaces that mimic the cogs of a nanoscale gear. The variation in the pitch lengths regulates the strain induced in capped graphene revealed by scanning probe techniques, Raman spectroscopy, and molecular dynamics simulation. The atomistic visualization elucidates asymmetric straining of CC bonds over the corrugated architecture resulting in distinct friction dissipation with respect to the groove axis. Experimental results are reported for strain-dependent solid lubrication which can be regulated by the corrugation and leads to ultralow frictional forces. The results are applicable for graphene covered corrugated structures with movable components such as nanoelectromechanical systems, nanoscale gears, and robotics., (© 2021 Wiley-VCH GmbH.)

This study explores the use of biochar (BC), an inexpensive filtration media, for removing graphene oxide (GO) contaminants from the aquatic subsurface environments. Mass balance approaches and column dissection tests were used to analyze the retention behavior of GO in a series of model fixed-bed columns as a function of ionic strength (IS) and flowrate. The column based on the biochar media (BC) displayed 3.6-fold higher retention compared to the quartz sand (control). To overcome the challenges of unfavorable electrostatic interactions between GO and BC, we used a facile functionalization strategy to modify the BC surfaces with nanoscale zero-valent iron (BC-nZVI). The BC-nZVI (5:1, w/w) retained 2.6-fold higher amounts of GO compared with bare biochar. Furthermore, the performance of BC-nZVI increased with decreasing values of IS, attributed to the attachment of GO to nZVI where nZVI was partially dissolved by the presence of higher chloride ion at high IS. A better GO retention (86%) at higher IS was observed in BC where the GO was primarily retained due to the higher aggregation via straining., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Published by Elsevier Ltd.)

Graphene is a promising material for many biointerface applications in engineering, medical, and life-science domains. Here, we explore the protection ability of graphene atomic layers to metals exposed to aggressive sulfate-reducing bacteria implicated in corrosion. Although the graphene layers on copper (Cu) surfaces did not prevent the bacterial attachment and biofilm growth, they effectively restricted the biogenic sulfide attack. Interestingly, single-layered graphene (SLG) worsened the biogenic sulfide attack by 5-fold compared to bare Cu. In contrast, multilayered graphene (MLG) on Cu restricted the attack by 10-fold and 1.4-fold compared to SLG-Cu and bare Cu, respectively. We combined experimental and computational studies to discern the anomalous behavior of SLG-Cu compared to MLG-Cu. We also report that MLG on Ni offers superior protection ability compared to SLG. Finally, we demonstrate the effect of defects, including double vacancy defects and grain boundaries on the protection ability of atomic graphene layers.

This study reports the use of multi-layered reduced graphene oxide (rGO) coating on porous nickel foam (NF) electrodes for enhancing biofilm growth of Rhodobacter Sphaeroides spp fed with methanol in microbial fuel cells (CH 3 OH-MFCs). Electrochemical methods were used to assess the methylotrophic activity on rGO/NF electrodes. The power density and current density offered by rGO/NF (1200 mW m -2 and 680 mA m -2 ) were 220-fold and 540-fold higher compared to bare NF (5.50 mW m -2 and 1.26 mA m -2 ), respectively. Electrochemical impedance spectroscopy results show that rGO/NF suppresses charge transfer resistance to CH 3 OH oxidation by 40-fold compared to the control. This improved performance is due to the ability of rGO coatings to decrease the wetting contact angle (improve the hydrophilicity) of NF from 128 0 to 0 0 . A preliminary cost analysis was carried out to assess the viability of rGO/NF electrodes via vitamin-C-enabled graphene oxide chemistry for CH 3 OH-MFCs applications., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Biodiesel is a widely used fuel that meets the renewable fuel standards developed under the Energy Policy Act of 2005. However, biodiesel is known to pose a series of abiotic and biotic corrosion risks to storage tanks. A typical practice (incumbent system) used to protect the tanks from these risks include (i) coating the interior surface of the tank with a solvent-free epoxy (SFE) liner, and (ii) adding a biocide to the tank. Herein, we present a screening-level life-cycle assessment study to compare the environmental performance of a graphene oxide (GO)-epoxy (GOE) liner with the incumbent system. TRACI was used as an impact assessment tool to model the midpoint environmental impacts in ten categories: global warming potential (GWP, kg CO 2 eq.); acidification potential (AP, kg SO 2 eq.); potential human health damage impacts due to carcinogens (HH-CP, CTU h ) and non-carcinogens (HH-NCP, CTU h ); potential respiratory effects (REP, kg PM 2.5 eq.); eutrophication potential (EP, kg N eq.); ozone depletion potential (ODP kg CFC-11 eq.); ecotoxicity potential (ETXP, CTU e ); smog formation potential (SFP kg O 3 eq.) and fossil fuel depletion potential (FFDP MJ surplus). The equivalent functional unit of the LCA study was designed to protect 30 m 2 of the interior surface (unalloyed steel sheet) of a 10 000 liter biodiesel tank against abiotic and biotic corrosion during its service life of 20 years. Overall, this LCA study highlights the improved environmental performance for the GOE liner compared to the incumbent system, whereby the GOE liner showed 91% lower impacts in ODP impact category, 59% smaller in REP, 62% smaller in AP, 67-69% smaller in GWP and HH-CP, 72-76% smaller in EP, SFP, and FFDP, and 81-83% smaller ETXP and HH-NCP category results. The scenario analysis study revealed that these potential impacts change by less than 15% when the GOE liners are functionalized with silanized-GO nanosheets or GO-reinforced polyvinyl carbazole to improve the antimicrobial properties. The results from an uncertainty analysis indicated that the impacts for the incumbent system were more sensitive to changes in the key modeling parameters compared to that for the GOE liner system.

Prevention of microbially induced corrosion (MIC) is of great significance in many environmental applications. Here, we report the use of an ultra-thin, graphene skin (Gr) as a superior anti-MIC coating over two commercial polymeric coatings, Parylene-C (PA) and Polyurethane (PU). We find that Nickel (Ni) dissolution in a corrosion cell with Gr-coated Ni is an order of magnitude lower than that of PA and PU coated electrodes. Electrochemical analysis reveals that the Gr coating offers ~10 and ~100 fold improvement in MIC resistance over PU and PA coatings respectively. This finding is remarkable considering that the Gr coating (1-2 nm) is ~25 and ~4000 times thinner than the PA (40-50 nm), and PU coatings (20-80 μm), respectively. Conventional polymer coatings are either non-conformal when deposited or degrade under the action of microbial processes, while the electro-chemically inert graphene coating is both resistant to microbial attack and is extremely conformal and defect-free. Finally, we provide a brief discussion regarding the effectiveness of as-grown vs. transferred graphene films for anti-MIC applications. While the as-grown graphene films are devoid of major defects, wet transfer of graphene is shown to introduce large scale defects that make it less suitable for the current application.