Density Shift Research Articles

Manipulating metal-oxygen local atomic structures in single-junctional p-Si/WO3 photocathodes for efficient solar hydrogen generation

Self-passivation in aqueous solution and sluggish surface reaction kinetics significantly limit the photoelectrochemical (PEC) performances of silicon-based photoelectrodes. Herein, a WO3 thin layer is deposited on the p-Si substrate by pulsed laser deposition (PLD), acting as a photocathode for PEC hydrogen generation. Compared to bare p-Si, the single-junctional p-Si/WO3 photoelectrodes exhibit excellent and stable PEC performances with significantly increased cathodic photocurrent density and exceptional anodic shift in onset potential for water reduction. It is revealed that the WO3 layer could reduce the charge transfer resistance across the electrode/electrolyte interface by eliminating the effect of Fermi level pinning on the surface of p-Si. More importantly, by varying the oxygen pressures during PLD, the collaborative modulation of W-O bond covalency and WO6 octahedral structure symmetry contributes to the promoted charge carrier transport and separation. Meanwhile, a large band bending at the p-Si/WO3 junction, induced by the optimized O vacancy contents in WO3, could provide a photovoltage as high as ∼ 500 mV to efficiently drive charge transfer to overcome the water reduction overpotential. Synergistically, by manipulating W-O local atomic structures in the deposited WO3 layer, a great improvement in PEC performance could be achieved over the single-junctional p-Si/WO3 photocathodes for solar hydrogen generation.

Ultra-fast luminescence of nano-gold film structure

The Fermi level of gold is not in the band gap, but in the sp band. Therefore, macroscopic gold is usually a non-luminescent material. Unlike gold bulk materials, frequency down-conversion photoluminescence and enhanced photoluminescence from gold nanoparticles have been studied, and the intensity of their photoluminescence is affected by the size, shape and plasmon resonance of the gold nanoparticles. In particular, plasmon resonance helps to increase the photoluminescence intensity by several times than the intensity in the macroscopic gold structure. Gold nanoparticles can also produce photoluminescence including second harmonic and third harmonic under intense photo excitation. Here, in order to study the luminescence properties of gold nanostructures under femtosecond laser, we applied a 5 nm gold film on a Si3N4 substrate by magnetron sputtering. The nano-gold film was excited using a femtosecond laser with an incident peak power density of 2.3 × 109 W/cm2 and 4.5 × 109 W/cm2. We explained that by studying the excitation spectra of nano-gold structures, we can see that SHG occurs at high power density and frequency shift occurs.

Mutual influence of tetrel and halogen bonds between XCN (X=Cl, Br) and 4-TF3-pyridine (T=C, Si, Ge).

Interplay between tetrel and halogen bonds in the XCN⋯4-TF3-pyridine⋯XCN (X=Cl, Br; T=C, Si, Ge) and 4-TF3-pyridine⋯XCN⋯4-TF3-pyridine complexes was studied by using quantum chemical methods. The respective binary complexes XCN⋯4-TF3-pyridine and 4-TF3-pyridine⋯XCN have also been investigated. Mutual influence of both interactions has been analyzed in terms of the molecular electrostatic potential, binding distance, binding energy, electron density shift, and energy decomposition. Both the tetrel and halogen bonds have been strengthened in the ternary complexes. The cooperativity of the XCN⋯4-TF3-pyridine⋯XCN complex is more prominent than that of the 4-TF3-pyridine⋯XCN⋯4-TF3-pyridine complex. The variation of molecular electrostatic potentials in the binary complexes and the electron density shift of the complexes well explains this cooperative effect. Energy decomposition analysis revealed that the interactions are mainly dominated by electrostatic contribution; meanwhile, electrostatic contribution, induction, and dispersion enlarged in the ternary complexes.

Changes of Fermi surface topology due to the rhombohedral distortion in SnTe

Stoichiometric SnTe is theoretically a small gap semiconductor that undergoes a ferroelectric distortion on cooling. In reality however, crystals are always non-stoichiometric and metallic; the ferroelectric transition is therefore more accurately described as a polar structural transition. Here we study the Fermi surface using quantum oscillations as a function of pressure. We find the oscillation spectrum changes at high pressure, due to the suppression of the polar transition and less than 10 kbar is sufficient to stabilize the undistorted cubic lattice. This is accompanied by a large decrease in the Hall and electrical resistivity. Combined with our density functional theory (DFT) calculations and angle resolved photoemission spectroscopy (ARPES) measurements this suggests the Fermi surface $L$-pockets have lower mobility than the tubular Fermi surfaces that connect them. Also captured in our DFT calculations is a small widening of the band gap and shift in density of states for the polar phase. Additionally we find the unusual phenomenon of a linear magnetoresistance that exists irrespective of the distortion that we attribute to regions of the Fermi surface with high curvature.

Chemical interaction and electronic structure in a compositionally complex alloy: A case study by means of X-ray absorption and X-ray photoelectron spectroscopy

Chemical interaction and changes in local electronic structure of Cr, Fe, Co, Ni and Cu transition metals (TMs) upon formation of an Al8Co17Cr17Cu8Fe17Ni33 compositionally complex alloy (CCA) have been studied by X-ray absorption spectroscopy and X-ray photoelectron spectroscopy. It was found that upon CCA formation, occupancy of the Cr, Co and Ni 3d states changes and the maximum of the occupied and empty Ni 3d states density shifts away from Fermi level (Ef) by 0.5 and 0.6 eV, respectively, whereas the Cr 3d empty states maximum shifts towards Ef by 0.3 eV, compared to the corresponding pure metals. The absence of significant charge transfer between the elements was established, pointing to the balancing of the 3d states occupancy change by involvement of delocalized 4s and 4p states into the charge redistribution. Despite the expected formation of strong Al–TMs covalent bonds, the Al role in the transformation of the TMs 3d electronic states is negligible. The work demonstrates a decisive role of Cr in the Ni local electronic structure transformation and suggests formation of directional Ni–Cr bonds with covalent character. These findings can be helpful for tuning deformation properties and phase stability of the CCA.

Corrosion characteristics of sintered heterogeneous materials composed of iron and iron oxides

Abstract In a coronary angioplasty or orthopaedic surgery, metallic implants are often used to provide mechanical support to the healing tissues. In some situations, this support is really needed only temporarily. After tissue recovery, the implant no longer provides any benefits and can trigger adverse reactions. An optimal solution might be the short-term implants which are able to decompose in situ and can be readily excreted from the body. Iron-based materials are promising candidates for application in biodegradable devices. For the successful application, the ability to control the material’s corrosion rate is important. In this contribution, the corrosion of iron-iron oxide composites is investigated. In order to obtain such materials, iron-oxide granules were incompletely reduced, compacted and sintered. Materials consisting of a pure iron and iron oxides were obtained. Specimens from as-sintered materials and materials reduced once again after sintering were prepared. Potentiodynamic polarization testing in Hanks’ solution indicated that specimens underwent a galvanic corrosion, where the release of ferrous ions from iron surfaces represents the anodic reaction and the oxygen reduction on surfaces of both iron and iron oxides represents the cathodic reaction. Changes in the content of oxides resulted in anticipated shifts in corrosion potential and apparent corrosion current density.

Effect of Nb addition on the microstructural, mechanical and electrochemical characteristics of AlCrFeNiCu high-entropy alloy

AlCrFeNiCuNbx (x = 0.05, 0.15, and 0.26) high-entropy alloys (HEAs) were successfully fabricated using the laser metal deposition technique. The laser power of 1600 W and scanning speed of 1.2 m/min were used during laser processing of the alloys. The microstructural, mechanical, and electrochemical characteristics of the alloys were evaluated using various advanced characterization techniques. Results showed that the alloys exhibited a dual-phase structure with dendritic grains. The inclusion of Nb in the AlCrFeNiCu alloy matrix promoted the formation of fine eutectic structures and changed the shape of the grains from columnar to equiaxed. The Cu content decreased with the increase in the content of Nb, whereas the Al content increased with the increase in the content of Nb. The findings indicated that the presence of Nb in the alloy promoted the formation and enhanced the stability of the body-centered cubic (bcc) phase. All of the alloys that contained Nb also exhibited high hardness, compressive strength, and wear resistance. Furthermore, the low current density and positive shift in potential exhibited by HEAs with appropriate addition of Nb highlighted the superior anticorrosive properties.

Mammal population densities at a global scale are higher in human‐modified areas

Global landscapes are changing due to human activities with consequences for both biodiversity and ecosystems. For single species, terrestrial mammal population densities have shown mixed responses to human pressure, with both increasing and decreasing densities reported in the literature. How the impacts of human activities on mammal populations translates into altered global density patterns remains unclear. Here we aim to disentangle the effect of human impacts on large‐scale patterns of mammal population densities using a global dataset of 6729 population density estimates for 468 mammal species (representing 59% and 44% of mammalian orders and families). We fitted a mixed effect model to explain the variation in density based on a 1‐degree resolution as a function of the human footprint index (HFI), a global proxy of direct and indirect human disturbances, while accounting for body mass, trophic level and primary productivity (normalized vegetation index; NDVI). We found a significant positive relationship between population density and HFI, where population densities were higher in areas with a higher HFI (e.g. agricultural or suburban areas – no populations were located in very high HFI urban areas) compared to areas with a low HFI (e.g. wilderness areas). We also tested the effect of the individual components of the HFI and still found a consistent positive effect. The relationships remained positive even across populations of the same species, although variability among species was high. Our results indicate shifts in mammal population densities in human modified landscapes, which is due to the combined effect of species filtering, increased resources and a possible reduction in competition and predation. Our study provides further evidence that macroecological patterns are being altered by human activities, where some species will benefit from these activities, while others will be negatively impacted or even extirpated.

Switchable Adhesion of E. coli to Thermosensitive Carbohydrate-Presenting Microgel Layers: A Single-Cell Force Spectroscopy Study

Adhesion processes at the cellular scale are dominated by carbohydrate interactions, including the attachment and invasion of pathogens. Carbohydrate-presenting responsive polymers can bind pathogens and inhibit pathogen invasion by remote stimuli for the development of new antibiotic strategies. In this work, the adhesion forces of E. coli to monolayers composed of mannose-functionalized microgels with thermosensitive poly(N-isopropylacrylamide) (PNIPAM) and poly(oligo(ethylene glycol)) (PEG) networks are quantified using single-cell force spectroscopy (SCFS). When exceeding the microgels' lower critical solution temperature (LCST), the adhesion increases up to 2.5-fold depending on the polymer backbone and the mannose density. For similar mannose densities, the softer PNIPAM microgels show a significantly stronger adhesion increase when crossing the LCST as compared to the stiffer PEG microgels. This is explained by a stronger shift in swelling, mannose density, and surface roughness of the softer gels when crossing the LCST. When using nonbinding galactose instead of mannose, or when inhibiting bacterial receptors, a certain level of adhesion remains, indicating that also polymer-fimbria entanglements contribute to adhesion. The presented quantitative analysis provides insights into carbohydrate-mediated bacterial adhesion and the relation to material properties and shows the prospects and limitations of interactive polymer materials to control the attachment of bacteria.

Gradient tantalum-doped hematite homojunction photoanode improves both photocurrents and turn-on voltage for solar water splitting

Hematite has a great potential as a photoanode for photoelectrochemical (PEC) water splitting by converting solar energy into hydrogen fuels, but the solar-to-hydrogen conversion efficiency of state-of-the-art hematite photoelectrodes are still far below the values required for practical hydrogen production. Here, we report a core-shell formation of gradient tantalum-doped hematite homojunction nanorods by combination of hydrothermal regrowth strategy and hybrid microwave annealing, which enhances the photocurrent density and reduces the turn-on voltage simultaneously. The unusual bi-functional effects originate from the passivation of the surface states and intrinsic built-in electric field by the homojunction formation. The additional driving force provided by the field can effectively suppress charge–carrier recombination both in the bulk and on the surface of hematite, especially at lower potentials. Moreover, the synthesized homojunction shows a remarkable synergy with NiFe(OH)x cocatalyst with significant additional improvements of photocurrent density and cathodic shift of turn-on voltage. The work has nicely demonstrated multiple collaborative strategies of gradient doping, homojunction formation, and cocatalyst modification, and the concept could shed light on designing and constructing the efficient nanostructures of semiconductor photoelectrodes in the field of solar energy conversion.

The reactivity of cinnamic acid derivatives as lignin precursors

Objectives. Cinnamic acid derivatives belong to a large class of phenolic compounds, which are widely distributed in plants and have high potential for use in the medical and industrial fields. They have various useful practical properties, e.g., antioxidant, anti-inflammatory, antiplatelet, and anti-melanogenic properties. Hydroxycinnamic acids are of particular interest as phenylpropanoids, which are the starting compounds of lignin. The aim of this work was to study the electronic structure and analyze the reactivity of the simplest representatives of phenylpropanoids formed during the biosynthesis of the coumaric (p-hydroxycinnamic), caffeic (3,4-dihydroxycinnamic), ferulic (3-methoxy-4-hydroxycinnamic), sinapic (3,5-dimethoxy-4- hydroxycinnamic), and 3,4-dimethoxycinnamic acids. These acids are the biogenetic precursors of most other phenolic compounds (coumarins, melanins, lignins, and flavonoids) and are found in almost all higher plants.Methods.Calculations with full optimization of the geometric parameters were performed using the original Hartree–Fock theory and hybrid density functional method. All calculations were performed using the Firefly program.Results.A comparative quantum chemical calculation of the geometric parameters of hydroxycinnamic acid molecules was conducted via two methods, and the values of the charges on atoms according to Mulliken were determined. It was found that with the addition of hydroxyl and methoxy substituents at the meta and para positions relative to the carboxyl fragment, the electron density shifts toward the benzene ring, and the symmetry of the molecule decreases. Additionally, in these structures, there is π,π-conjugation of the carboxyl fragment of the –СН=СНСООН molecule with the aromatic ring, which significantly affects the geometric configuration of the molecule. The maximum positive charge is concentrated on the C9 atom, while the maximum negative charge is on the oxygen atoms belonging to the methoxy substituents and the hydroxyl group, which confirms the role of oxygen atoms in the chemical transformations of acids.Conclusions.Two different methods were used to calculate the geometric, electronic, and energy parameters and electrophilicity indices of the studied hydroxycinnamic acids in the gas phase. The obtained values were consistent (within the limits of error) with the experimental data as well as the results described in earlier works’ calculations by other methods.

Quantitative stable isotope probing with H218O to measure taxon‐specific microbial growth

AbstractMicroorganisms in soil assimilate, transform, and mineralize soil C to support growth. There are an estimated 2.6 × 1029 microbial cells containing 26 Pg C in soils worldwide. Consequently, quantifying microbial growth in soil is critical for determining the degree to which microorganisms contribute to the global C cycle. Measuring taxonspecific microbial growth enables understanding of the contribution of microbial taxa to elemental transformations across ecosystems and their susceptibility to environmental perturbations. These measurements in soil have largely been lacking due to inadequate methods. Quantitative stable isotope probing (qSIP) with H218O is used to measure taxon‐specific growth of microbial taxa in soil, an improvement compared with traditional stable isotope probing (SIP). In qSIP, DNA extracted from both a labeled (18O‐enriched water) and an unlabeled treatment is separated into numerous density fractions by isopycnic centrifugation, and target genes are quantified and sequenced in each fraction. The taxon‐specific DNA density shift and ultimately the isotopic composition (18O enrichment) is calculated for each taxon. Here we discuss methods and illustrate the procedure for quantifying microbial taxon‐specific growth in soil with qSIP using heavy isotope enriched H218O.

The impact of anisotropy on ITER scenarios

We report on the impact of anisotropy to tokamak plasma configuration and stability. Our focus is on analysis of the impact of anisotropy on ITER pre-fusion power operation 5 MA, B = 1.8 T ICRH scenarios. To model ITER scenarios remapping tools are developed to distinguish the impact of pressure anisotropy from the change in magnetic geometry caused by an anisotropy-modified current profile. The remappings iterate the anisotropy-modified current-density profile to produce the same q profile with matched thermal energy. The analysis is a step toward equilibria that are kinetically self-consistent for a prescribed scenario. We find characteristic detachment of flux surfaces from pressure surfaces and an outboard (inboard) shift of peak density for ( ). Differences in the poloidal current profile are evident, albeit not as pronounced as for the spherical tokamak. We find that the incompressional continuum is largely unchanged in the presence of anisotropy and the mode structure of gap modes is largely unchanged. The compressional branch however exhibits significant differences in the continuum. We report on the implication of these modifications.

Evaluating the Long-Term Trend and Management of a Globally Important Loggerhead Population Nesting on Masirah Island, Sultanate of Oman

Nest count surveys provide an important means for tracking trends in marine turtle populations. In 2015 the IUCN Red List global status review changed the loggerhead turtle (Carretta caretta) from Endangered to Vulnerable status, and, with a revised regional management unit (RMU) assessment system in place, concluded that the Northwest Indian Ocean loggerhead turtle RMU was Critically Endangered (CR). We analyzed annual time series nest count survey data between 1978 and 2016 to evaluate population trend and characterize the existing spatial and temporal attributes of a globally significant rookery on Masirah Island, Oman. A two-point trend assessment using a subset of historical data (1985-1996) combined with recent data (2008-2016) on a representative, 9-km section of index beaches revealed a change from 584 tracks-1 km-1 season-1 (SD = 109.5) to 122.43 tracks-1 km-1 season-1 (SD = 37.3), representing a statistically significant 79% decline. Comparative data were tested for spatial and temporal conformity, and the influence of other parameters on the trend result were considered, such as nesting success ratios and spatial shifts in density. Our analyses confirm that the decline occurred within a single loggerhead generation. Mean multiyear nest counts from recent surveys provides an estimate of 55,202 nests year-1 (SD=16,814, CI 0.95 53,326- 57,078) across 83 km of nesting beach. Considering recent clutch frequency estimates the mean number of nesting loggerheads per year is estimated between 10,223 (CI 0.95 9,875- 10,570) and 11,500 (CI 0.95 11,109- 11,891). The Northwest Indian Ocean RMU is thought to represent 35% of the global nesting population. Recognizing a pressing need to address the decline in this population we identify potential threats on nesting beaches and at sea which point towards priority actions for conservation of this CR RMU.

Triangular Expanded Hemiporphyrazines: Electronic Structures and Nanoscale Characterization of Their Adlayers on Au(111)

Abstract Electronic structures and direct observation of adlayers on Au(111) of triangular expanded hemiporphyrazines that can be classified into azaporphyrinoids and which can trap three transition metal ions are reported. The electronic structure was examined by electronic absorption and magnetic circular dichroism (MCD) spectroscopies and interpreted in conjunction with molecular orbital (MO) calculations. Both metal-free and metallated compounds were 30 π-electron systems with n = 7 in 4n + 2 aromaticity. In addition, calculations of the anisotropy of the induced current density (ACID) and nucleus-independent chemical shift (NICS) were performed. The inner core region of the metal-free compound was weakly anti-aromatic or nonaromatic, but after metal insertion, this region increased aromatic character. The direct observation of adlayers of one of their cobalt and nickel complexes on Au(111) by scanning tunneling microscopy (STM) revealed that these three ions are arranged specifically in the shape of a triangle.

Projecting the future vegetation–climate system over East Asia and its RCP-dependence

The future vegetation–climate system over East Asia, as well as its dependence on Representative Concentration Pathways (RCPs), is investigated using a regional climate–vegetation model driven with boundary conditions from Flexible Global Ocean–Atmosphere–Land System Model: Grid-point Version 2. Over most of the region, due to the rising CO2 concentration and climate changes, the model projects greater vegetation density (leaf area index) and gradual shifts of vegetation type from bare ground to grass or from grass to trees; the projected spatial extent of the vegetation shift increases from RCP2.6 to RCP8.5. Abrupt shifts are projected under RCP8.5 over northeast China (with grass replacing boreal needleleaf evergreen trees due to heat stress) and India (with tropical deciduous trees replacing grass due to increased water availability). The impact of vegetation feedback on future precipitation is relatively weak, while its impact on temperature is more evident, especially during DJF over northeast China and India with differing mechanisms. In northeast China, the projected forest loss induces a cooling through increased albedo, and daytime high temperature (Tmax) is influenced more than nighttime low temperature (Tmin); in India, increased vegetation cover induces an evaporative cooling that outweighs the warming effect of an albedo decrease in DJF, leading to a weaker impact on Tmax than on Tmin. Based on a single model, the qualitative aspects of these results may hold while quantitative assessment will benefit from a follow-up regional model ensemble study driven by multiple general circulation models.

Noncovalent Bonds between Tetrel Atoms.

The pairing of TFH3 with a TH2 CH3 - anion, where T represents tetrel atoms C, Si, Ge, Sn, Pb, results in a strong direct interaction between the two T atoms. The interaction energy is sensitive to the nature of the two T atoms but can be as large as 90 kcal/mol. The noncovalent bond strength rises quickly as the basic T atom of the anion becomes smaller, or as the Lewis acid T grows larger, although there is less sensitivity to the latter atom. The electrostatic component makes up some 55-70 % of the total attraction energy. This term is well accounted for by simple combination of the maximum and minimum values of the molecular electrostatic potential of the Lewis acid and base units, respectively. The complexation induces a rearrangement in the TFH3 molecule from tetrahedral to trigonal pyramidal. The associated deformation energy reduces the exothermicity of the complexation reaction. Electron density shift patterns reveal a density loss on the basic T atom, along with accompanying increases on the acidic T and its attached F atom.

How to address the issue of uniformity in large area capacitively coupled plasmas? A modeling investigation

Recently, the electrical asymmetry effect (EAE) has been proven effective not only in separate control of the ion energy and ion flux, but also in modulation of the plasma radial uniformity. Since no major change in reactor constructions is required, this method is promising and of significant importance in the plasma industry. In this work, a two-dimensional electromagnetic fluid model is employed to investigate the influence of the EAE on the plasma density distribution under various voltages (i.e., the peak-to-peak voltage V0 equals to 33 V, 56 V and 100 V) and pressures (i.e., 50 mTorr, 200 mTorr and 750 mTorr), in H2 capacitively coupled plasma (CCP) discharges sustained by multiple consecutive harmonics. The results indicate that at V0 = 33 V or 750 mTorr, the plasma density is characterized by a broad maximum at the radial center, and the effectiveness of the EAE on the modulation of the plasma radial uniformity is limited. When V0 becomes higher, the plasma distribution varies obviously by adjusting the phase shift of the fundamental frequency θ1. For instance, when θ1 increases from 0 to 2π at V0 = 56 V, the plasma density shifts from uniform over center-high to uniform. Moreover, at V0 = 100 V, the best uniformity is observed at θ1 = π. When the pressure decreases to 50 mTorr, although the uniformity varies significantly with θ1, the plasma density stays low, which may not be welcomed in the plasma processing. Different influences of the EAE on the plasma radial uniformity can be understood by examining the electron heating induced by the sheath expansion and the electric field reversal under various discharge conditions. The results obtained in this work could help us to have a better understanding of the EAE on the plasma radial uniformity, which would be useful to improve the plasma processing in large area CCP reactors.

Dioxygen Activation by Internally Aromatic Metallacycle: Crystallographic Structure and Mechanistic Investigations.

SummaryMononuclear metal-peroxo species are invoked as the key intermediates in metalloenzymatic or synthetic catalysis. However, either transience or sluggishness reactivity of synthetic analogs of metal-peroxo species impedes our understanding of oxygen activation mechanism. Herein, we designed and characterized a dioxygen-derived mononuclear osmium-peroxo complex, in which the peroxo ligand is stabilized by internally aromatic metallacycle. We demonstrate that the osmium-peroxo species shows catalytic activity toward promoterless alcohol dehydrogenations. Furthermore, computational studies provide a new mechanism for the osmium-peroxo-mediated alcohol oxidation, starting with the concerted double-hydrogen transfer and followed by the generation of osmium-oxo species. Interestingly, the internally aromatic metallacycle also plays a vital role in catalysis, which mediates the hydrogen transfer from osmium center to the distal oxygen atom of Os–OOH moiety, thus facilitating the Os–OOH→Os=O conversion. We expect that these insights will advance the development of aromatic metallacycle toward aerobic oxidation catalysis.

Successive ionic layer adsorption and reaction (SILAR) deposition of nickel sulfide on the Fe2O3 nanotube for efficient photocathodic protection of stainless steel under visible light

Nickel sulfide deposited on the Fe2O3 nanotube surfaces (NiS/Fe2O3) via successive ionic layer adsorption and reaction (SILAR) method was applied as a novel photoanode in the photocathodic protection in order to retard the corrosion of 403 stainless steel. The morphology, crystal structure, and elemental composition were characterized by scanning electron microscopy, X-ray diffraction, and energy dispersive X-ray. Furthermore, measurements of the open-circuit potential, photocurrent density with time (j − t), and potentiodynamic polarization curves (Tafel plot) were used to assess the photocathodic protection effects of the films prepared. The morphology, visible light response, and the corresponding photoelectrochemical performances of NiS/Fe2O3 were affected by the number of SILAR cycles. Considerable photoelectrochemical properties such as enhanced photocurrent density and negative shift corrosion potential were shown by NiS/Fe2O3 in comparison with bare Fe2O3 nanotubes. Optimal photoelectrochemical characteristics were shown by NiS/Fe2O3 prepared with 5 SILAR cycles (sample C5), based on the results obtained. Improved photocathodic protection effect was shown by the novel NiS/Fe2O3 films as photoanodes, causing the potential of the coupled stainless steel in 3.5% NaCl solution to decrease by 200 mV relative to its corrosion potential.