Sulfide Interface Research Articles

MOF-derived CoS2/WS2 electrocatalysts with sulfurized interface for high-efficiency hydrogen evolution reaction: Synthesis, characterization and DFT calculations

Developing high-efficiency, economical and non-noble-metal electrocatalysts is of great importance to produce hydrogen through hydrogen evolution reaction (HER) in water splitting. Transition metal dichalcogenide has received increasing interests in the application in efficient catalysis, energy conversion and storage. Now, a unique bimetallic sulfide composite (CoS2/WS2) has been prepared by calcination and one-pot hydrothermal method using metal–organic frameworks (MOFs) as precursors. The presence of suitable thioacetamide (TAA) plays a great role in forming the best sulfide interface between CoS2 and WS2 to enhance HER performance. Herein, the overpotential and Tafel slope of as-synthesized CoS2/WS2 at 10 mA cm−2 in 0.5 M H2SO4 medium are obtained as 79 mV and 52 mV dec–1, respectively, which are much lower than those of most non-noble metal-based electrocatalysts. Density Functional Theory (DFT) calculations verify that the bimetallic configuration through the sulfide interface changes the electronic structure, enhances the electrical conductivity and reduces the hydrogen adsorption energy (ΔGH*), effectively accelerating the Heyrovsky step in the HER process. Meanwhile, CoS2/WS2 shows excellent stability in durability tests. The method proposed in this work provides a feasible solution for synthesizing low-cost electrocatalysts.

Synergistic interaction of S anions with 3d electrons in the bismuth sulfide/iron sulfide interface for simultaneous overall water splitting, urea oxidation, and methanol oxidation

Lotus-flower-like heterostructures of Bi2S3/FeS with diverse morphologies and stoichiometries were successfully synthesized using a facile hydrothermal technique. The flower-like architecture and FeS content were controlled by adjusting the amount of l-cysteine during precursor synthesis. Electrochemical properties were explored through a combination of Raman and impedance spectroscopy, revealing the relationship between catalytic performance and the stoichiometry of Bi2S3/FeS. Due to the synergistic interaction of S anions with 3d electrons at the Bi2S3/FeS interface the heterostructures exhibited highly enriched overall water-splitting ability, achieving a remarkably low cathodic and anodic overpotential of 36 and 230 mV for a current density of 10 mA/cm2. Furthermore, the addition of methanol and urea in the electrolyte further enhanced the catalytic efficiency of Bi2S3/FeS, achieving a very high current density of 100 mA/cm2 at exceptionally low potentials of 1.5 V and 1.43 V for methanol and urea oxidation reaction. The excellent electrocatalytic properties of Bi2S3/FeS were attributed to the interactions and interfacial effects between Bi2S3 and FeS, leading to enhanced surface roughness, inhomogeneity, and the creation of additional electrochemically active sites. Notably, Bi2S3/FeS demonstrated long-term stability and excellent mass transportation capabilities, highlighting its potential for various practical applications. The remarkable element gradient in the heterostructures further contributes to their superior performance, making them highly promising candidates for diverse applications.

From two sensors to a single sensor: Better understanding of oxygen–sulfide interfaces

AbstractIntense biogeochemical transformations in sediments and biofilms may occur over sub‐mm distances. Our current understanding of those transformations in such narrowly stratified environments has been facilitated by the introduction of microsensors. Until now most studies have been conducted using individual sensors for the various chemical species, and careful vertical alignment of the sensor tips is then essential for the meaningful interpretation of the resulting data. For instance, the determination of total dissolved sulfide (TDS) at high resolution requires perfect alignment of sensors for H2S and pH, as the pKa for H2S is close to ambient pH. In this study, we show how a recently developed TDS sensor and a new combined H2S/O2microsensor can improve the analysis of sulfidic environments including the oxygen–sulfide interface. The TDS sensor does not require pH correction unlike the conventional H2S sensor, and it thus eliminates the need for a simultaneous pH measurement. The combined sensor allows for perfect alignment of H2S and O2micro profiles and makes it possible to not only more accurately estimate fluxes, but also to determine overlapping zones of oxygen and dissolved sulfide at very high resolution.

Possible Ways to Improve Interphase Adhesion between Fiberglass and Polyphenylenesulfide

The article presents a scientific review on the development of composite materials based on polyphenylene sulfide and glass fillers. The main ways (finishing of the filler surface, synthesis of a polymer matrix with functional groups, treatment of the filler and polymer matrix surface with a plasma flow) of increasing interfacial adhesion at the glass fiber-polyphenylene sulfide interface are considered.

Photovoltaic characteristics and computational simulation of samarium-ion doped Cu(In, Ga)Se2 thin films prepared via a non-vacuum coating process

The effects of samarium ions on the photovoltaic performance of Cu(In, Ga)Se2 (CIGS) films were investigated through experiments and computational simulation. Compared with pristine CIGS films, the conversion efficiency of the prepared solar cells increased by 26.6% (from 8.62% to 10.91%) when 0.5 mol% samarium ions were doped into CIGS films. The incorporation of 0.5 mol% samarium ions facilitated the formation of the Cu2−xSe phase during the selenization reaction. The Cu2−xSe phase as the flux agent melted at high temperatures and thus promoted the growth of CIGS grains and reduced the number of surface pores on CIGS films. The smooth morphology of 0.5 mol% samarium-ion doped CIGS films improved the coverage of the buffer layers and suppressed the formation of additional shunt paths, thereby decreasing defect density in the CIGS/cadmium sulfide (CdS) interface and the absorber layer. The simulated results revealed the incorporation of 0.5 mol% samarium ions reduced the defect density from 1 × 1011 cm−3 to 1 × 109 cm−3 in the CIGS/CdS interface and from 3 × 1017 cm−3 to 4 × 1016 cm−3 in the absorber layers. The shunt conductance and saturation current of the prepared solar cells also decreased, from 4.38 mS/cm2 to 2.60 mS/cm2 and from 7.25 × 10−3 mA/cm2 to 1.31 × 10−3 mA/cm2, respectively. Excess doping of samarium ions caused a residual Cu2−xSe phase in CIGS films and resulted in the formation of additional shunt paths to deteriorate the performance of CIGS solar cells. The incorporation of appropriate concentrations of samarium ions into CIGS films was an effective approach to improve the photovoltaic properties of CIGS solar cells.

Anion-Modulated Platinum for High-Performance Multifunctional Electrocatalysis toward HER, HOR, and ORR.

SummaryEfficient electrocatalyst toward hydrogen evolution/oxidation reactions (HER/HOR) and oxygen reduction reaction (ORR) is desirable for water splitting, fuel cells, etc. Herein, we report an advanced platinum phosphide (PtP2) material with only 3.5 wt % Pt loading embedded in phosphorus and nitrogen dual-doped carbon (PNC) layer (PtP2@PNC). The obtained catalyst exhibits robust HER, HOR, and ORR performance. For the HER, a much low overpotential of 8 mV is required to achieve the current density of 10 mA cm−2 compared with Pt/C (22 mV). For the HOR, its mass activity (MA) at an overpotential of 40 mV is 2.3-fold over that of the Pt/C catalyst. Interestingly, PtP2@PNC also shows exceptional ORR MA which is 2.6 times higher than that of Pt/C and has robust stability in alkaline solutions. Undoubtedly, this work reveals that PtP2@PNC can be employed as nanocatalysts with an impressive catalytic activity and stability for broad applications in electrocatalysis.

Using modern low-oxygen marine ecosystems to understand the nitrogen cycle of the Paleo- and Mesoproterozoic oceans.

During the productive Paleoproterozoic (2.4-1.8Ga) and less productive Mesoproterozoic (1.8-1.0Ga), the ocean was suboxic to anoxic and multicellular organisms had not yet evolved. Here, we link geologic information about the Proterozoic ocean to microbial processes in modern low-oxygen systems. High iron concentrations and rates of Fe cycling in the Proterozoic are the largest differences from modern oxygen-deficient zones. In anoxic waters, which composed most of the Paleoproterozoic and~40% of the Mesoproterozoic ocean, nitrogen cycling dominated. Rates of N2 production by denitrification and anammox were likely linked to sinking organic matter fluxes and in situ primary productivity under anoxic conditions. Additionally autotrophic denitrifiers could have used reduced iron or methane. 50% of the Mesoproterozoic ocean may have been suboxic, promoting nitrification and metal oxidation in the suboxic water and N2 O and N2 production by partial and complete denitrification in anoxic zones in organic aggregates. Sulfidic conditions may have composed ~10% of the Mesoproterozoic ocean focused along continental margins. Due to low nitrate concentrations in offshore regions, anammox bacteria likely dominated N2 production immediately above sulfidic zones, but in coastal regions, higher nitrate concentrations probably promoted complete S-oxidizing autotrophic denitrification at the sulfide interface.

BSA mediated Ag@Bi2S3 composites: synthesis, characterization, photodegradation of mixed dyes via metal-semiconductor interface, antimicrobial and antioxidant activities

Nowadays, the development of metal-metal sulfide interface semiconductors using green approach is best material for the photocatalytic and biological applications. Here, we provided for the first time, an environmentally friendly route to fabricate bovine serum albumin (BSA) assisted Ag@Bi2S3 composites through a metal-metal sulphide interface via a simple hydrothermal method for the evaluation of photochemical and biological applications. The synthesized composites were characterized by UV–vis DRS, PL, XRD, TEM, and N2 adsorption-desorption isotherms. The UV–vis DRS and PL spectra show that the obtained nano-sized Ag@Bi2S3 composite displays enhanced visible-light absorption and a decreased fluorescence emission compared to that of Bi2S3 nanorods (NRs). The photocatalytic performances of the synthesized composites were evaluated by the degradation of the single (RhB and MB) and mixed dye (RhB+MB) under sunlight irradiation. The results indicated that the Ag@Bi2S3 composite exhibits superior photocatalytic activity (98.38%) than that of individual Ag NPs and Bi2S3 NRs due to the synergistic effect of Ag and Bi2S3 nanophases in the Ag@Bi2S3 composite, which results in an effective charge separation, fast electron transfer from Ag to Bi2S3, and a low recombination of photo-induced electron-hole pairs. The Ag@Bi2S3 composite also has good recycling stability up to 5 cycles and its mechanism also investigated. The evaluation of reactive species during the photocatalytic reaction was also carried out. Further, the effects of Bi2S3 and Ag NPs on the antimicrobial and antioxidant activity of the resultant Ag@Bi2S3 composite were also systematically investigated.

Oxygen Vacancies Dominated NiS2/CoS2 Interface Porous Nanowires for Portable Zn–Air Batteries Driven Water Splitting Devices

The development of highly active and stable oxygen evolution reaction (OER) electrocatalysts is crucial for improving the efficiency of water splitting and metal-air battery devices. Herein, an efficient strategy is demonstrated for making the oxygen vacancies dominated cobalt-nickel sulfide interface porous nanowires (NiS2 /CoS2 -O NWs) for boosting OER catalysis through in situ electrochemical reaction of NiS2 /CoS2 interface NWs. Because of the abundant oxygen vacancies and interface porous nanowires structure, they can catalyze the OER efficiently with a low overpotential of 235 mV at j = 10 mA cm-2 and remarkable long-term stability in 1.0 m KOH. The home-made rechargeable portable Zn-air batteries by using NiS2 /CoS2 -O NWs as the air-cathode display a very high open-circuit voltage of 1.49 V, which can maintain for more than 30 h. Most importantly, a highly efficient self-driven water splitting device is designed with NiS2 /CoS2 -O NWs as both anode and cathode, powered by two-series-connected NiS2 /CoS2 -O NWs-based portable Zn-air batteries. The present work opens a new way for designing oxygen vacancies dominated interface nanowires as highly efficient multifunctional electrocatalysts for electrochemical reactions and renewable energy devices.

Interfacial trap-induced confinement of mobile carriers during illumination at a pentacene/lead-sulfide functional interface

Interfacial electronic properties at the pentacene/lead sulfide (PbS) interface in the dark under illumination were studied. With a small size of PbS colloidal quantum dot (CQD) (2.7 nm), photoinduced charge transfer at the pentacene/PbS CQD interface leads to a large threshold voltage shift in a pentacene/PbS CQD field effect transistor (FET). Through estimation of interfacial trap density by sub-threshold slope measurements in an FET structure, the mechanism by which threshold voltage shift occurs is discussed.

Exciton dissociation and energy transfer at the quantized pentacene/lead-sulfide nanocrystal functional interface

We investigated quantized-charge and energy transfer at the pentacene/lead sulfide (PbS) interface through realization of PbS nanocrystal (NC) size-dependent quantum confinement effect, providing insights into the presence of triplet exciton dissociation and energy transfer. With PbS nanocrystals (NCs) of a small size (∼3 nm), quantized charge and energy transfer at the pentacene/PbS NC interface leads to a large photocurrent while PbS NCs of a large size (∼7 nm) causes a far reduced photocurrent. Through comparison between the normal and inverted structures, importantly, exciton dissociation and energy transfer are turned out to be sensitive to subtle structural change at the interface.

Charged and Discharged States of Cathode/Sulfide Electrolyte Interfaces in All-Solid-State Lithium Ion Batteries

Interfaces between cathodes and sulfide electrolytes exhibit high resistance in all-solid-state lithium ion batteries. In this paper, to elucidate the origin of the high interface resistance we have theoretically investigated the properties of the cathode interfaces with the sulfide electrolyte and oxide electrolyte for comparison. From the density functional molecular dynamics simulations of the LiFePO4/Li3PS4 interface in both discharged and charged states, we have demonstrated the instability of the sulfide interface in the charged state, that is, the lithium depletion and oxidation on the sulfide side near the interface, in contrast to the oxide interfaces. The obtained results imply the formation of a Li-depleted layer around the sulfide interfaces during charging and support the validity of the insertion of oxide buffer layers at the interface to reduce the interface resistance.

Cadmium sulfide interface layer for improving the performance of titanium dioxide/poly (3-hexylthiophene) solar cells by extending the spectral response

This work focused on studying the effect of cadmium sulfide (CdS) interfacial layer on the performance of titanium dioxide (TiO2)/poly (3-hexylthiophene) (P3HT) solar cells and finding out its effect on charge recombination dynamics of hybrid TiO2/P3HT solar cells. FESEM images confirm the uniform distribution of chemical bath deposited CdS layer on TiO2 nanoparticles. Insertion of CdS layer at the nanocrystalline TiO2/P3HT interface broadens quantum efficiency spectrum of the solar cells with peak values over 80 and 40 % at the wavelengths of maximum absorption of CdS and P3HT respectively and hence enhances short-circuit current density (JSC) from 3.5 to 5.9 mAcm−2 under simulated illumination (70 mWcm−2) with an AM 1.5 filter. CdS layer further improves open circuit voltage (VOC) from 0.35 to 0.57 V, which is consistent with higher built-in voltage in CdS/P3HT than in TiO2/P3HT due to relatively lower laying conduction band edge of CdS. Photovoltaic transient measurements show that the carrier life-time in TiO2/CdS/P3HT solar cell is an order of magnitude longer than that in TiO2/P3HT solar cell. Optimized TiO2/P3HT solar cells with CdS interlayer yield power conversion efficiencies over 1.5 %, which is three times greater than that for similar solar cells without CdS layer.

Piezo-phototronic Boolean logic and computation using photon and strain dual-gated nanowire transistors.

Using polarization charges created at the metal-cadmium sulfide interface under strain to gate/modulate electrical transport and optoelectronic processes of charge carriers, the piezo-phototronic effect is applied to process mechanical and optical stimuli into electronic controlling signals. The cascade nanowire networks are demonstrated for achieving logic gates, binary computations, and gated D latches to store information carried by these stimuli.

Chalcogen Atom Interaction with Palladium and the Complex Molecule–Metal Interface in Thiol Self Assembly

In the case of reactive metals, on adsorption of organic chalcogenide molecules like thiols, chalcogenide-C bond scission can occur. Thus, the high reactivity of Pd leads to initial thiol dissociation and formation of a complex PdS interface layer on which thereafter thiol self-assembled monolayers (SAM) can form. In this context we investigate in detail the adsorption of S, Se, alkanethiols, and aromatic dithiols on Pd by photoemission with synchrotron radiation. The nature of the PdS and PdSe layers formed is studied, and thiol adsorption on Pd(111), PdS, and PdSe surfaces is investigated, along with interface characteristics. After initial strong sulfidation (selenization) in Na2S(Se) solutions, a well-ordered surface PdS (PdSe) layer can be obtained by annealing. For S, annealing leads to formation of a PdS (√7 × √7)R19.1° layer, whereas for Se, large domains of this structure are formed. Experiments suggest that in thiol adsorption the Pd–sulfide interface is not simply similar to the (√7 × √7)R19.1° PdS layer but that modifications in this surface sulfide layer are induced. A similar effect is observed on the selenide interface layer. In addition, 1,4-benzenedimethanethiol adsorption on Pd is investigated with the aim of creation of thiol-terminated dithiol molecular layers. Unlike the case of surfaces like Au, no clear indication of a standing-up, thiol-terminated SAM was found. X-ray radiation damage effects are reported.

Vertical distribution of planktonic autotrophic thiobacilli and dark CO2 fixation rates in lakes with oxygen–sulfide interfaces

AME Aquatic Microbial Ecology Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials AME 59:217-228 (2010) - DOI: https://doi.org/10.3354/ame01399 Vertical distribution of planktonic autotrophic thiobacilli and dark CO2 fixation rates in lakes with oxygen–sulfide interfaces Emilio O. Casamayor* Department of Continental Ecology-Limnology, Centre d’Estudis Avançats de Blanes-CSIC, Accès Cala St. Francesc 14, 17300 Blanes, Spain *Email: casamayor@ceab.csic.es ABSTRACT: Vertical distributions of viable (most probable number, MPN) aerobic chemoautotrophic thiobacilli-like sulfur-oxidizing bacteria (ca. 70 samples in triplicate for MPN counts) and dark 14C-bicarbonate incorporation rates were analyzed in a series of sulfide-rich lakes. A special device for sampling sharply stratified populations on the scale of a few centimeters was used. Detailed analyses focused on the oxic-anoxic transition zone where aerobic sulfur-oxidizing bacteria should display positive chemotaxis, and in both fully oxic epilimnia and sulfide-rich anoxic hypolimnia. Kinetics of sulfide and thiosulfate potential oxidations in the presence of oxygen were followed in microcosm enrichments in one of the lakes. The highest MPN counts (>104 to 105 cells ml–1) were observed at the oxic-anoxic interfaces and in the depleted hypolimnia (1.3 ± 4.4 × 104 cells ml–1), whereas 1 order of magnitude lower concentrations were detected in the epilimnia (1.0 ± 2.3× 103 cells ml–1). Dark 14C-bicarbonate incorporation rates were higher at the oxic-anoxic interface (11.4 ± 9.5 µg C l–1 h–1) than in the hypolimnia (6.4 ± 5.9 µg C l–1 h–1) and epilimnia (1.0 ± 2.1 µg C l–1 h–1). A lack of correspondence between abundance of MPN thiobacilli, location at the sulfide interface, and dark carbon fixation rates was, however, consistently observed in a correlation analysis. Patterns of in situ potential aerobic thiosulfate oxidation did not match dark carbon fixation rates or MPN vertical distributions. The chemoautotrophic guild of these lakes emerged as a metabolically complex, taxonomically diverse group of aerobic, microaerophilic, and anaerobic microorganisms coexisting in the same lake. Thiobacilli may actively fix CO2 at certain depths but the question of which types of bacteria contribute most to dark CO2 fixation in the investigated lakes is still open, and the application of culture-independent molecular tools and single-cell analyses should be used to substantiate and further explore these findings. KEY WORDS: Thiobacilli · Karstic lake · Sulfide · Oxic-anoxic interface · Most probable number · Dark CO2 fixation Full text in pdf format PreviousNextCite this article as: Casamayor EO (2010) Vertical distribution of planktonic autotrophic thiobacilli and dark CO2 fixation rates in lakes with oxygen–sulfide interfaces. Aquat Microb Ecol 59:217-228. https://doi.org/10.3354/ame01399 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AME Vol. 59, No. 3. Online publication date: April 14, 2010 Print ISSN: 0948-3055; Online ISSN: 1616-1564 Copyright © 2010 Inter-Research.

Origin of kamacite, schreibersite, and perryite in metal‐sulfide nodules of the enstatite chondrite Sahara 97072 (EH3)

Abstract– Perryite [(Fe,Ni)x(Si,P)y], schreibersite [(Fe,Ni)3P], and kamacite (αFeNi) are constituent minerals of the metal‐sulfide nodules in the Sahara 97072 (EH3) enstatite chondrite meteorite. We have measured concentrations of Ni, Cu, Ga, Au, Ir, Ru, and Pd in these minerals with laser ablation, inductively coupled plasma mass spectrometry (ICP‐MS). We also measured their Fe, Ni, P, Si, and Co concentrations with electron microprobe. In kamacite, ratios of Ru/Ir, Pd/Ir, and Pd/Ru cluster around their respective CI values and all elements analyzed plot near the intersection of the equilibrium condensation trajectory versus Ni and the respective CI ratios. In schreibersite, the Pd/Ru ratio is near the CI value and perryite contains significant Cu, Ga, and Pd. We propose that schreibersite and perryite formed separately near the condensation temperatures of P and Si in a reduced gas and were incorporated into Fe‐Ni alloy. Upon further cooling, sulfidation of Fe in kamacite resulted in the formation of additional perryite at the sulfide interface. Still later, transient heating re‐melted this perryite near the Fe‐FeS eutectic temperature during partial melting of the metal‐sulfide nodules. The metal‐sulfide nodules are pre‐accretionary objects that retain CI ratios of most siderophile elements, although they have experienced transient heating events.

Support-controlled chemoselective olefin—imine addition photocatalyzed by cadmium sulfide on a zinc sulfide carrier

The semiconductor catalyzed photoaddition of cyclopentene or cyclohexene to various novel electron-poor imines of type p-XC(6)H(4)(CN)C[double bond, length as m-dash]N(COPh) (X = H, F, Cl, Br, Me, MeO) was investigated as a function of the nature of the cadmium sulfide photocatalyst. Irradiation (lambda>/= 350 nm) of silica supported cadmium sulfide surprisingly did not afford the expected olefin-imine adducts but an imine hydrocyanation product via an unprecedented dark reaction. However, when silica was replaced by zinc sulfide as the support for cadmium sulfide, the expected homoallylic N-benzoyl-alpha-amino cyanides were isolated in yields of 65-84%. Thus, chemoselectivity is introduced through replacing an insulating by a semiconducting support, a hitherto unknown effect in semiconductor photocatalysis. From the sign of the time resolved photovoltage it is found that the mixed metal sulfide interface CdS/ZnS increases the lifetime of photogenerated electron-hole pairs by about one order of magnitude as compared to the SiO(2)/CdS system. The reaction rate increases with increasing imine sigma-Hammett constants and decreasing stability of intermediate benzyl radicals.

Influence of sodium compounds at the Cu(In,Ga)Se 2/(PVD)In 2S 3 interface on solar cell properties

The present contribution deals with indium sulfide buffer layers grown by thermal co-evaporation of elemental indium and sulfur. It has been found necessary to deposit these buffer layers at low substrate temperatures in order to reach V oc values similar to those with (CBD)CdS. However, such deposition conditions lead to the formation of a highly recombinative Cu(In,Ga)Se 2/indium sulfide interface. This behaviour may be associated to the presence of sodium carbonates/oxides at the interface even though the Cu(In,Ga)Se 2 surface was cleaned in NH 3 (1 M, room temperature) prior to the indium sulfide deposition. An explanation is that, despite the chemical etch, sodium carbonates/oxides remain in the air exposed Cu(In,Ga)Se 2 grain boundaries and can migrate towards the surface when the Cu(In,Ga)Se 2 is heated under vacuum. These polluted interface areas act as recombination zones and thus inferior devices. A possibility to improve the device performance (i.e. improve the interface quality) is to sulfurize the remaining sodium carbonates/oxides. The resulting Na 2S can then leave the interface by formation of a solid solution with the indium sulfide. By adapting the buffer layer deposition process, 13.3% efficiency devices with co-evaporated indium sulfide are realized, performance which is close to that reached with (CBD)CdS.

Metal sulfide semiconductor electrochemical mechanisms induced by bacterial activity

Various bacterial species (e.g. Thiobacilli, Leptospirillum) have adapted to utilize solid inorganic semiconducting sulfides (e.g. FeS 2, ZnS, CuFeS 2) as their energy source for carbon dioxide fixation. The interfacial electrochemical mechanisms which they apply have practical relevance for bioleaching of minerals, acid mine pollution, for the biocorrosion of steel, and for solar powered chemosynthesis based on the bacterial energy cycle. The bacterial attack on the sulfide surface is based on the use of recyclable chemical species (H +, Fe 2+, thiol-compound) which disrupt chemical bonds in the sulfide interface and thereby induce disintegration. Model experiments performed with 100-nm thin synthetic FeS 2 layers allowed a detailed study of the interaction between bacterial cells and the pyrite interface. Thiobacillus ferrooxidans uses an organic polysaccharide layer to extract sulfur in the form of colloids via a cysteine-based carrier molecule. The mechanism which leads to corrosion pit formation of bacterial size could be analyzed in great detail. Addition of a surface active agent was found to induce increasingly localized leaching activity of bacterial cells. Addition of cysteine stimulates bacterial activity and acts as a sulfide dissolving agent even in the absence of bacteria. Mechanisms to block bacterial attack were identified on the basis of thiol chemistry. Leptospirillum ferrooxidans was found to apply a different strategy. It can only exist on Fe 2+ oxidation and dissolves FeS 2 by pushing — via a very positive Fe 2+/3+ redox potential, generated within the organic capsula — the semiconductor towards the electrochemical dissolution potential. The FeS 2 interface thus disintegrates into small fragments from which free energy of electrons for Fe 3+ reduction is utilized. Two isostructural materials with analogous electronic structure, FeS 2 which serves as energy source for T. ferrooxidans and RuS 2 which cannot at all be oxidized, are compared in detail to understand the molecular aspects of bacteria-induced semiconductor electrochemistry.