Hydrophilic Electrode Research Articles

Fast Outer-Sphere Electron Transfer and High Specific Capacitance at Covalently Modified Carbon Electrodes.

Carbon electrodes typically display sluggish electron transfer kinetics due to the adsorption of adventitious molecules that effectively insulate the surface. Here, we describe a method for rendering graphitic carbon electrodes permanently hydrophilic by functionalization with 4-(diazonium)benzenesulfonic acid. In aqueous electrolytes, these hydrophilic carbon electrodes exhibit metal-like specific capacitance (∼40 μF/cm2) as measured by cyclic voltammetry, suggesting a change in the double-layer structure at the carbon surface. Additionally, the modified electrodes show fast charge transfer kinetics to outer-sphere one-electron redox couples such as ferro-/ferricyanide as well as improved electron transfer kinetics in alkaline aqueous redox flow batteries.

Bacterial-Polyhydroxybutyrate for Biocompatible Microbial Electrodes

The development of bioelectrochemical systems requires careful selection of both their biotic and abiotic components to obtain sustainable devices. Herein, we report a biophotoelectrode obtained with polyhydroxybutyrate (PHB), a biopolymer, which purple non-sulphur bacteria produce as an energy stock under specific environmental conditions. The electrode was obtained by casting a mixture composed of PHB and carbon fibers in a 3:2 mass ratio. Following, the composite material was modified with polydopamine and thermally treated to obtain a hydrophilic electrode with improved electrochemical behavior. The bio-based electrode was tested with metabolically active cells of Rhodobacter capsulatus embedded in a biohybrid matrix of polydopamine. The system achieved enhanced catalytic activity under illumination, with an 18-fold increase in photocurrent production compared to biophotoelectrodes based on glassy carbon, reaching a current density of 12 ± 3 μA cm−2, after 30 min of light exposure at +0.32 V. The presented biocompatible electrode provides a sustainable alternative to metal-based and critical raw material-based electrodes for bioelectrochemical systems.

Sn/Sb–assisted alum sludge electrodes for eliminating hydrophilic organic pollutants in self-produced H2O2 electro-Fenton system: Insights into the co-oxidation mediated by 1O2 and •OH(ads)

Few reports have focused on using particle electrodes with polar adsorbent properties in heterogeneous electro-Fenton (EF) system to improve the degradation of hydrophilic organic pollutants (HLOPs). In this study, a hydrophilic electrode Sn–Sb/AS was prepared by supporting metals Sn and Sb on alum sludge (AS), which can effectively degrade 91.68%, 92.54%, 89.62%, and 96.24% of the four types of HLOPs, chlorpyrifos (CPF), atrazine (ATZ), diuron (DIU), and glyphosate (PMG), respectively, within 40 min. The mineralization rates were 82.37%, 78.93%, 73.98%, and 85.65% for CPF, ATZ, DIU, and PMG, respectively. Based on the analysis of Electron Paramagnetic Resonance test, quenching test, and identified anthracene endoperoxide, the degradation at the cathode was attributed to non-radical oxidation via interaction with 1O2. In contrast, the anodic oxidation occurred via direct electron transfer at the anode and/or oxidation via interaction with adsorbed •OH (•OHads) around the particle electrodes. Furthermore, the reaction sites were calculated by Density functional theory (DFT) and Fukui function, corresponding to the electrophilic attack (fA-) of 1O2 and anodic direct oxidation, besides, the radical attack (fA0) of •OH(ads). Herein, this study proposes a targeted elimination strategy for HLOPs in wastewater treatment using particle electrodes with polar adsorbent properties in EF system.

On-The-Spot Sampling and Detection of Viral Particles on Solid Surfaces Using a Sponge Virus Sensor Incorporated with Finger-Press Fluid Release.

This paper presents a sponge-based electrochemical sensor for rapid, on-site collection and analysis of infectious viruses on solid surfaces. The device utilizes a conducting porous sponge modified with graphene, graphene oxide, and specific antibodies. The sponge serves as a hydrophilic porous electrode capable of liquid collection and electrochemical measurements. The device operation involves spraying an aqueous solution on a target surface, swiping the misted surface using the sponge, discharging an electrolyte solution with a simple finger press, and performing in situ incubation and electrochemical measurements. By leveraging the water-absorbing ability of the biofunctionalized conducting sponge, the sensor can effectively collect and quantify virus particles from the surface. The portability of the device is enhanced by introducing a push-release feature that dispenses the liquid electrolyte from a miniature reservoir onto the sensor surface. This reservoir has sharp edges to rupture a liquid sealing film with a finger press. The ability of the device to sample and quantify viral particles is demonstrated by using influenza A virus as the model. The sensor provided a calculated limit of detection of 0.4 TCID50/mL for H1N1 virus, along with a practical concentration range from 1-106 TCID50/mL. Additionally, it achieves a 15% collection efficiency from single-run swiping on a tabletop surface. This versatile device allows for convenient on-site virus detection within minutes, eliminating the need for sample pretreatment and simplifying the entire sample collecting and measuring process. This device presents significant potential for rapid virus detection on solid surfaces.

Promoting hydrophilic cupric oxide electrochemical carbon dioxide reduction to methanol via interfacial engineering modulation

Copper-based catalysts have been extensively investigated in electrochemical carbon dioxide (CO2) reduction to promote carbon products generated by requiring multiple electron transfer. However, hydrophilic electrodes are unfavourable for CO2 mass transfer and preferentially hydrogen (H2) evolution in electrochemical CO2 reduction. In this paper, a hydrophilic cupric oxide (CuO) electrode with a grassy morphology was prepared. CuO-derived Cu was confirmed as the active site for electrochemical CO2 reduction through wettability modulation. To enhance the intrinsic catalytic activity, a metal-oxide heterogeneous interface was created by engineering modulation at the interface, involving the loading of palladium (Pd) on CuO (CuO/Pd). Both the electrochemically active area and the electron transfer rate were enhanced by Pd loading, and significantly the reduced work function further facilitated the electron transfer between the electrode surface and the electrolyte. Consequently, the CuO/Pd electrode exhibited excellent excellent performance in electrochemical CO2 reduction, achieving a 54 % Faraday efficiency at −0.65 V for methanol (CH3OH). The metal-oxide interfacial effect potentially improves the intrinsic catalytic activity of hydrophilic CuO electrodes in electrochemical CO2 reduction, providing a conducive pathway for optimizing hydrophilic oxide electrodes in this process.

Sustainable solar-and electro-driven production of high concentration H2O2 coupled to electrocatalytic upcycling of polyethylene terephthalate plastic waste

The photoelectro-reforming of poly (ethylene terephthalate) (PET) waste coupled with the synthesis of hydrogen peroxide (H2O2) poses significant implications for environmental and energy engineering, yet it presents substantial with challenges. A strategy offering an energy efficient photo-electrolysis is reported, which couples oxygen reduction reaction (ORR) with oxidation reaction of PET hydrolysate (glycol, EGOR), utilizating a porous hollow double-shell with oxygen vacancies Z-scheme Mo2N-Co3O4@Fe2O3/PVDF/NF cathode and a Co3O4/NF anode within a cell electrolyser. The H2O2 concentration by hydrophobic photocathode (3.4 wt%) significantly surpasses that of hydrophilic electrode (1.9 wt%), attributing to the hydrophobic modified enhances the mass transfer and utilization efficiency of O2. The Mo2N-Co3O4@Fe2O3 has photothermal effect by introducing Mo2N with local surface plasmon resonance (LSPR) for the direct synthesis of high concentration H2O2 (21.4 wt%). The photoelectro-reforming of PET by photoanode yields the value-added products such as terephthalic acid (PTA) and potassium diformate (KDF) with a high Faradic efffciency (89 %). Notably, EGOR assistes the ORR, resulting in a yield of H2O2 by ORR that is significantly improved at least three times in comparison to the water oxidation reaction coordinated with ORR. This research contributes to a feasible methodology for H2O2 production, and the transformation of plastics and other waste materials into value-added chemicals.

Synchronous generation of H2O2 and high effective removal of inorganic arsenic/organoarsenic by visible light-driven cell

A Janus photocathode of asymmetric wettability with hydrophobic oxygen storage layer and hydrophilic catalyst layer was successfully fabricated by graphite felt (GF) polytetrafluoroethylene (PTFE)-hydrophobization and a subsequent hollow sphere NiFe2O4 @ZnFe2O4 (NF@ZF) Z-scheme photocatalysts coating on the other side of GF. The designed Janus electrode showed significantly higher H2O2 production than hydrophilic (NF@ZF/GF) and hydrophobic (NF@ZF/PTFE/GF) electrodes, and achieved a higher faradaic efficiency of 72%, as well as a record H2O2 production rate of 255.9 mg·L−1∙h−1, while maintaining a stable photoelectrochemical performance for 9 h at 2.8 mA∙cm−2 in Na2SO4 solution. The two-electrode co-photoelectrolysis system by coupling the ORR with inorganic arsenic/organoarsenic oxidation can simultaneously produce H2O2 at Janus photocathode and As (V) at Fe anode under a low energy consumption (a cell voltage of only 0.7 V), respectively, and then the generated As (V) could be rapidly removed (above 93%) by adsorption onto Fe (III) (hydro)oxides.

Understanding the potentiometric response of cation-permselective hydrophilic nanopore-based electrodes in the low ion concentration range

Permselective membranes are at the core of important applications and devices, that include ion-selective electrodes, energy conversion, and separation. Here we report the potential response in the low ion concentration range of hydrophilic cation-permselective gold nanopore-based membranes obtained by surface modification with a sulfonate-bearing thiol derivative. Apart from conventional polymeric permselective membranes, we confirmed ‘equal’ potentiometric responses for the same valency cations, that include both inorganic and organic cations. A refined Nernst–Planck/Poisson (NPP) model to account for previously neglected mass transport effects in the low ion concentration domain was shown to accurately predict even the interesting zero current fluxes generated super-Nernstian responses for higher valency cations. For all investigated ions we found that their interaction with sulfonate-groups functionalized nanopores is dominantly electrostatic in its nature. Hence, the synthetic versatility of such permselective nanopores in conjunction with the possibility of a rational design of its properties based on the NPP model renders such nanopore-based membranes not only a convenient alternative to existent permselective membranes, but their unique properties show promises for novel ion-sensing and separation applications.

Wettability-modulated ordered mesoporous carbon electrodes for electrocatalytic reactions involving gases

Herein, a series of ordered mesoporous carbon (OMC) electrodes with switchable surface wettability were developed. These electrodes are favorable for water electrolysis at high current densities and increase the production of H2O2 in the oxygen reduction reaction. The hydrophilic OMC electrodes can promote the oxygen evolution reaction performance by separating O2 bubbles promptly. The hydrophobic OMC electrodes provide a directional diffusion channel for O2 transport to improve the efficiency of O2 utilization. The hydrophobic OMC electrode is used for green synthesis of H2O2 with a production rate of 48.1 mmol gcat−1 h−1, Faraday efficiency of 86.3%, and minimum energy consumption of 3.07 kWh kg−1. The constructed electro-Fenton system reached 87% and 73% removal rate of rhodamine B and methyl orange within 60 min, respectively. The hydrophilic/hydrophobic electrodes are expected to have an important function in electrocatalytic reactions involving gases.

Triple-Phase Interface Engineering over an In2O3 Electrode to Boost Carbon Dioxide Electroreduction.

The electrocatalytic reduction of CO2 is deemed to be a promising method to ease environmental and energy issues. However, achieving high efficiency and selectivity of CO2 electroreduction remains a bottleneck due to huge limitation of CO2 mass transfer and competition of hydrogen evolution reaction (HER) in aqueous solution. In this work, we propose to utilize triple-phase interface engineering over an In2O3 electrode to enhance its CO2 reduction reaction (CO2RR) performance. Notably, distinguishing from other research studies (doping, defect introduction, and heterojunction construction) that regulate the nature of In2O3-based catalysts themselves, we herein tune interfacial wettability of In2O3 using facile fluoropolymer coating for the first time. In contrast to the hydrophilic In2O3 electrode [Faraday efficiency (FE)HCOOH ∼ 62.7% and FEH2 ∼ 24.1% at -0.67 V versus RHE], the hydrophobic fluoropolymer (taking polyvinylidene fluoride as an example)-coated In2O3 electrode delivers a significantly enhanced FEHCOOH of 82.3% and a decreased FEH2 of 5.7% at the same potential. Upon combining contact angle measurements, density functional theory calculation, and ab initio molecular dynamics simulation, the enhanced CO2RR performance is revealed to be attributed to the rich triple-phase interfaces formed after fluoropolymer coating as an "aerophilic sponge", which increases the local concentration of CO2 near In2O3 active sites to improve CO2 reduction and meanwhile reduces the accessible water molecules to suppress competitive HER. This work presents a feasible approach for the enhanced selectivity of HCOOH yield over In2O3 by triple-phase interface engineering, which also provides a convenient and effective method for developing other materials used in gas-consumption reactions.

Decorated fractal Ni-Cu foam with Pd nanoparticles as a high-performance electrocatalyst toward hydrogen evolution reaction

• The Ni-Cu foam was decorated with Pd nanoparticles by galvanic replacement method. • The Tafel slope of Ni-Cu/Pd is 72 mV dec −1 which is 94 mV dec −1 less than substrate. • The fractal architecture of Ni-Cu/Pd provided a high surface area (112.5 cm 2 ). • Ni-Cu/Pd requires 134 mV overpotential at the current density of 10 mA cm −2 . Fractal Ni-Cu foam with palladium nanoparticles on (Ni-Cu foam / Pd) was prepared by electrodeposition and galvanic replacement method. The results showed that after the fabrication of Pd particles on Ni-Cu foam, the hydrogen evolution reaction (HER) activity of the electrode improved dramatically. The morphology and phase structure of deposited layers were studied by field emission scanning electron microscopy, and X-ray diffraction methods, respectively. In order to investigate the morphology of the coatings in more details, transmission electron microscope was used, which its figures authenticated the presence of Pd nanoparticles on the fractal structures of Ni-Cu. Based on the electrochemical tests in KOH (1.0 M), the Ni-Cu foam / Pd electrode has good electrocatalytic properties, with a low overpotential of 134 mV at 10 mA cm −2 and Tafel slope of 72 mV dec −1 . Cyclic voltammetry measurements showed that the Ni-Cu foam/Pd possesses a high electrochemical surface area of 112.5 cm 2 that was attributed to the presence of both fractal Ni-Cu foam and Pd nanoparticles. Overall, this study proposes a feasible approach for the fabrication of a highly-porous, super hydrophilic, and scalable electrode with a great performance toward HER.

Enhanced electro-Fenton oxidation by introducing three-phase interface with simultaneous optimization of O2 and pollutant transfer for effective tetracycline hydrochloride removal

Mass transfer plays a dominating role in electro-Fenton (EF) system, where the transportations of gaseous O2 and dissolved pollutant were difficult to simultaneously optimize when using conventionally hydrophilic or hydrophobic electrodes (HIE/HOE). To overcome this difficulty, three-phase interface (TPI) was successfully introduced into sandwich electrode (SE) via an asymmetrical wettability design of hydrophilic catalyst on both sides of three-dimensional hydrophobic substrate. With the help of TPI in SE body, the rapid gaseous O2 transfer process led to the best OH generation of 536.4 μM, over 9 times than HIE (59.4 μM) with dissolved-O2 transfer limitation. Meanwhile, due to a large electrochemically-active area from hydrophilic catalyst layer, more exposed sites at SE surface could availably electro-adsorb 32.0% tetracycline hydrochloride (TC), ∼3.7 times than HOE with TC transfer restriction. Thanks to simultaneous optimization of O2 and pollutant transfer processes, the TPI-rich SE achieved an excellent TC mineralization of 68.0% (removal of 93.3%), far more than 9.3% of HIE and 14.7% of HOE. Therefore, this study paved an ingenious approach to mitigate two-phase (gas/liquid) transfer limitation in EF system for effective organic pollutants degradation.

All-Nanofiber-Based Janus Epidermal Electrode with Directional Sweat Permeability for Artifact-Free Biopotential Monitoring.

Epidermal electronics have been developed with gas/sweat permeability for long-term wearable electrophysiological monitoring. However, the state-of-the-art breathable epidermal electronics ignore the sweat accumulation and immersion at the skin/device interface, resulting in serious degradation of the interfacial conformality and adhesion, leading to signal artifacts with unstable and inaccurate biopotential measurements. Here, the authors present an all-nanofiber-based Janus epidermal electrode endowed with directional sweat transport properties for artifact-free biopotential monitoring. The designed Janus multilayered membrane (≈15µm) of superhydrophilic-hydrolyzed-polyacrylonitrile (HPAN)/polyurethane (PU)/Ag nanowire (AgNW) can quickly (less than 5 s) drive sweat away from the skin/electrode interface while resisting its penetration in the reverse direction. Along with the medical adhesive (MA)-reinforced junction-nodes, the adhesion strength among the heterogeneous interfaces can be greatly enhanced for robust mechanical-electrical stability. Therefore, their measured on-body electromyography (EMG) and electrocardiography (ECG) signals are free of sweat artifacts with negligible degradation and baseline drift compared to commercial Ag/AgCl gel electrodes and hydrophilic textile electrodes. This work paves a way to design novel directional-sweat-permeable epidermal electronics that can be conformally attached under sweaty conditions for long-term biopotential monitoring and shows the potential to apply epidermal electronics to many challenging conditions.

Flexible Capacitive Pressure Sensor Based on an Embedded Rib Fabric With a Bionic Sloping Petal Structure

High-performance flexible pressure sensors play an important role in the field of human body detection and human–computer interaction. This study proposes a new low-cost capacitive sensor that can achieve high sensitivity and stability over a wide range of tactile pressures (0–80 kPa). In addition, the nanowires were deposited into a flexible fabric that is embedded in polydimethylsiloxane to form a hydrophilic and hydrophobic layered electrode layer. The multilayer fiber structure of the rib fabric ensures good electrical conductivity. The sensitivity of the sensor that is made from the slanted bionic microstructure is seven times that of the dielectric layer without the microstructure. The measured response recovery time (13.4 ms) is suitable for real-time dynamic monitoring. Because a small temperature has little impact on the sensor, the sensor can be widely used in close-fitting wearable devices. It can also quickly identify the bending movement of the finger joints, as well as the finger pressure. Meanwhile, the sensor shows excellent stability and can withstand more than 7,000 load/unload cycle tests. This sensor has broad application prospects such as human health, motion monitoring, and human-computer interaction control.

Capillary enhanced hydrophilic block carbon material for binder-free supercapacitor electrode

Excellent wettability of electrode materials is an important prerequisite for high-efficiency energy storage devices. Inspired by the capillarity, we design a new type of block carbon material with vertical channel array that can generate capillary tension and then enhance the hydrophilicity in aqueous liquid. When applied to supercapacitors, this electrode not only exhibits an excellent affinity ( e.g., 0°) for aqueous electrolyte, but also can be directly utilized as an electrode without any additions. Electrochemical measurements demonstrate that this novel hydrophilic and binder-free electrode enjoys satisfactory performances including high capacitance ( e.g., 2452 mF cm −2 at 5 mA cm −2 ), long cycling life in coin-type device ( e.g., 100% after 10 000 cycles). Furthermore, the pure carbon-assembled quasi-solid-state supercapacitor could deliver an appealing energy density up to 5.49 mWh cm −2 at a power density of 50.0 mW cm −2 . This work presents the strategy of hydrophilic conversion of materials through rational structural construction for the first time, and demonstrates an ultra-facile supercapacitor electrode which is full of practical application value. • Block carbon material with vertical channels was designed. • Capillary effect caused by channels optimized the transport of electrolyte. • The electrode exhibited better electrochemical performance in supercapacitors.

Mesoscopic modeling impacts of liquid water saturation, and platinum distribution on gas transport resistances in a PEMFC catalyst layer

The oxygen transport resistance in catalyst layer of proton-exchange-membrane fuel cells has garnered much attention because it increases dramatically with the decreasing platinum loading. In this paper, the local transport behaviors of oxygen in electrode with different liquid water saturations, and platinum distributions are explored at mesoscopic level. The two-phase flow regime in electrode is simulated via a multicomponent multiphase flow model to reconstruct the liquid water morphologies. The effective oxygen diffusivities under wet conditions, the limiting current density, and the electrode resistance are numerically obtained before determining the local transport resistance. The results demonstrate that the effective oxygen diffusivities under wet condition decrease with the contact angle of the electrode. The limiting current density decreases with the liquid water saturation due to the blockage of ionomer surface area and the decreasing pore size distribution. The contribution of ionomer and liquid water to the electrode resistance dominates for the electrode resistance at low platinum loading. The local transport resistance of hydrophilic electrodes increases dramatically if the oxygen permeation in liquid water is excluded. More platinum particles distributed near the gas diffusion layer are beneficial for the reduction of the local transport resistance.

Janus graphite felt cathode dramatically enhance the H2O2 yield from O2 electroreduction by the hydrophilicity-hydrophobicity regulation

Hydrogen peroxide (H2O2) electrosynthesis from 2-electron O2 reduction reaction (2eORR) is widely regarded as a promising alternative to the current industry-dominant anthraquinone process. Design and fabrication of effective, low-cost carbon-based electrodes is one of the priorities. Many previous work well confirmed that hydrophilic carbon-based electrodes are preferable for 2eORR. Here, we proposed a strategy of hydrophilicity-hydrophobicity regulation. By using commercially available graphite felt (GF) as electrodes, we showed that both hydrophilic GF, hydrophobic GF, and Janus GF yielded significantly higher H2O2 production, which is 7.3 times, 7.6 times, and 7.7 times higher than the original GF, respectively. Results showed that currents and stirring rates affect the H2O2 yields. The enhancement of hydrophilic GF is due to the incorporation of oxygen-containing functional groups, while the hydrophobic and Janus GF comes from the locally confined O2 bubbles, which built a gas-liquid-solid interface inside GF and thus enhance the H2O2 formation kinetics. Finally, the effectiveness of the hydrophilicity-hydrophobicity regulation concept was tested in Electro-Fenton process by removing typical dyes and antibiotics. This work supply an effective but facile strategy to enhance the performance of carbon-based electrodes towards 2eORR by regulating the micro-environment of electrodes.

Enhanced flexible optoelectronic devices by controlling the wettability of an organic bifacial interlayer

Solution-processed flexible organic optoelectronic devices have great potential as low-cost organic photovoltaics for energy harvesting, and in organic light-emitting diodes as a lighting source. However, a major challenge for improving device performance and stability is the different interfacial characteristics of the hydrophobic organic layers and hydrophilic transparent electrodes, particularly for flexible devices. Surface wetting controlled interfacial engineering can provide a useful method to develop highly efficient flexible organic devices. Here, an unsaturated fatty acid-modified ethoxylated polyethyleneimine organic interfacial layer is designed, which is hydrophobic or hydrophilic on different interfaces. This interlayer results in a power conversion efficiency of 10.57% for rigid and 9.04% for flexible photovoltaic devices. Furthermore, the long-term air storage stability for 250 h is substantially improved, retaining 87.75% efficiency without encapsulation, due to the wettability driven improvement of the optical and electronic properties of the cathode interfacial layer. The performance of organic light emitting diodes also benefitted from the interlayer. This study provides a strategy to simultaneously improve efficiency and stability by controlling the wettability of the interfacial layer.

Triple-phase electrocatalysis for the enhanced CO2 reduction to HCOOH on a hydrophobic surface

The aqueous electrochemical reduction of CO2 into hydrocarbon fuels has been considered as a promising route to mitigate environmental problems. However, owing to the limited mass transfer of CO2 and competition with hydrogen evolution reaction in aqueous electrolyte solution, Sn-based catalysts exhibited low current density and low Faraday efficiency (FE), especially at high overpotential. Herein, we introduced a hydrophobic surface on Cu/Sn nanowires by decoration with trimethoxy (1H, 1H, 2H, 2H-heptadecafluorodecyl) silane (FAS). In contrast to the hydrophilic electrode (FEHCOOH-76.44%, at −1.2 V vs. RHE), the hydrophobic electrode achieved a high Faraday efficiency of 94.17% towards HCOOH production at −1.2 V vs. RHE. Remarkably, the synthesized electrode achieved an excellent activity for CO2 conversion even at high overpotential (FEHCOOH-86.39%, jHCOOH-23.95 mA cm−2, at −1.4 V vs. RHE), which far exceeded other most of Sn materials. This observation could be contributed to the rich triple-phase interfaces at the hydrophobic surface, which enhanced the CO2 mass transfer and increased the selectivity of HCOOH, especially at high overpotential. It was demonstrated that increasing CO2 mass transfer flux through the reduction of the wettability of the electrode was a facile and promising approach for the improved electrochemical CO2 reduction.

Electroactive biofilms on surface functionalized anodes: The anode respiring behavior of a novel electroactive bacterium, Desulfuromonas acetexigens

Surface chemistry is known to influence the formation, composition, and electroactivity of electron-conducting biofilms. However, understanding of the evolution of microbial composition during biofilm development and its impact on the electrochemical response is limited. Here we present voltammetric, microscopic and microbial community analysis of biofilms formed under fixed applied potential for modified graphite electrodes during early (90 h) and mature (340 h) growth phases. Electrodes modified to introduce hydrophilic groups (-NH2, -COOH and -OH) enhance early-stage biofilm formation compared to unmodified or electrodes modified with hydrophobic groups (-C2H5). In addition, early-stage films formed on hydrophilic electrodes are dominated by the gram-negative sulfur-reducing bacterium Desulfuromonas acetexigens while Geobacter sp. dominates on -C2H5 and unmodified electrodes. As biofilms mature, current generation becomes similar, and D. acetexigens dominates in all biofilms irrespective of surface chemistry. Electrochemistry of pure culture D. acetexigens biofilms reveal that this microbe is capable of forming electroactive biofilms producing considerable current density of > 9 A/m2 in a short period of potential-induced growth (~19 h following inoculation) using acetate as an electron donor. The inability of D. acetexigens biofilms to use H2 as a sole source electron donor for current generation shows promise for maximizing H2 recovery in single-chambered microbial electrolysis cell systems treating wastewaters.