Band Structure Research Articles

Experimental and ab initio studies of enhance photocatalytic efficiency of La-Doped ZnO/g-C3N4 nanocomposites for bromothymol blue dye degradation

The ability of photocatalysis to clean up environmental contamination, notably in the treatment of water and air, has received extensive research. The composite materials synthesized by the coprecipitation method were made of ZnO and graphitic carbon nitride (g-C3N4) with various concentrations of lanthanum doping (La-ZnO). It was discovered that La metal ions were evenly distributed throughout the layered stacking structures of ZnO nanosheet, which had an impact on the band structure and increased the rate of electron-hole separation and visible light absorption. First-principles calculations show that La-doped ZnO-gC3N4 possesses a direct band gap and a type-II band structure with the conduction band minimum and the valence band maximum located in separate layers. A built-in electric field from the gC3N4 to the La-doped ZnO has been established through an analysis of charge density difference, Bader charge, work function, and band alignment. The electron-hole pair becomes spatially separated as a result, which increases the photodegradation activity. High interfacial charge transfer, efficient charge separation and migration, and high visible light optical absorbance were caused by the direct coating of ZnO on an ultra-thin g-C3N4 layer. The 0.6% La-doped ZnO-gC3N4 degraded 97% of the bromothymol blue (BB) dye, which was four times higher than the bulk ZnO, which could remove only about 21% of the dye at the same time. The combined effects of lower photo corrosion, higher solar light usage owing to a hollow structure and heterostructured semiconductor photocatalysis contribute to this increased photocatalytic activity. The capacity of La-doped ZnO/g-C3N4 nanocomposite to effectively break down BB dye via photocatalysis suggests that it has the potential to address the problems associated with dye pollution in water systems.

Synergistic coupling of optical field and built-in electric field for lithium-sulfur batteries with high cyclabilities and energy densities

Photo-assisted lithium sulfur batteries (PA-LSBs) provide vital and sustainable protocols for promoting sulfur redox reactions via powerful photoinduced effects. However, precise control of the stepwise adsorption, diffusion and photocatalytic conversion of polysulfides at the surface of photocatalysts is required to accelerate the photo-assisted process. Herein, optical field and built-in electric field synergistically-assisted LSBs are developed with a p-n junction of Co3O4-TiO2 on the carbon cloth, possessing a spontaneously generated built-in electric field and a well-matched energy band structure with sulfur redox reactions. Under light irradiation, the directional migration of soluble polysulfides and the space separation of photogenerated carriers are achieved with the synergistical coupling of the optical field and built-in electric field to precisely regulate the selective deposition of Li2S and inhibit the shuttle effect via an effective photocatalytic-promoted process, leading to a maximum capacity of 1087 mAh g−1 at 2 C and a low capacity attenuation of 0.068% per cycle at 5 C. A high areal capacity of 9.6 mAh cm−2 and a great potential photo-charge process can be realized with light irradiation. Furthermore, the stability of lithium metal anodes is improved accordingly. This work demonstrates a new insight to develop high-performance LSBs with a multifield synergistical coupling protocol.

Ab initio property characterisation of thousands of previously unexplored 2D materials

We perform extensive density functional theory calculations to determine the stability and elementary properties of 4249 previously unexplored monolayer crystals. The monolayers comprise the most stable subset (energy within 0.1 eV/atom of the convex hull) of a larger portfolio of two-dimensional (2D) materials recently discovered using a deep generative model and systematic lattice decoration schemes. The relaxed 2D structures are run through the basic property workflow of the Computational 2D Materials Database (C2DB) to evaluate the dynamical stability and obtain the stiffness tensor, piezoelectric tensor, deformation potentials, Born and Bader charges, electronic band structure, effective masses, plasma frequency, Fermi surface, projected density of states, magnetic moments, magnetic exchange couplings, magnetic anisotropy, topological indices, optical- and infrared polarisability. We provide statistical overviews of the property data and highlight a few specific examples of interesting materials. Our work exposes previously unknown parts of the 2D chemical space and provides a basis for the discovery of 2D materials with specific properties. All data is available in the C2DB.

Probing the Band Splitting near the Γ Point in the van der Waals Magnetic Semiconductor CrSBr.

This study investigates the electronic band structure of chromium sulfur bromide (CrSBr) through comprehensive photoluminescence (PL) characterization. We clearly identify low-temperature optical transitions between two closely adjacent conduction-band states and two different valence-band states. The analysis on the PL data robustly unveils energy splittings, band gaps, and excitonic transitions across different thicknesses of CrSBr, from monolayer to bulk. Temperature-dependent PL measurements elucidate the stability of the band splitting below the Néel temperature, suggesting that magnons coupled with excitons are responsible for the symmetry breaking and brightening of the transitions from the secondary conduction band minimum (CBM2) to the global valence band maximum (VBM1). Collectively, these results not only reveal splitting in both the conduction and valence bands but also highlight a significant advance in our understanding of the interplay between the optical, electronic, and magnetic properties of antiferromagnetic two-dimensional van der Waals crystals.

Improved Thermoelectric Performance in Ga‐ and Te‐Co‐introduced Tetrahedrite Cu12Sb4S13

As an earth‐abundant, environment‐friendly, and cost‐effective material, tetrahedrite Cu12Sb4S13 has attracted much attention in thermoelectrics (TEs). However, the TE performance of the pristine Cu12Sb4S13 (CSS) is mediocre, thereby much improvement is required. In this work, both the electronic and phonon transports of the CSS are engineered using Ga2Te3 as a dopant. In the results, it is indicated that dual substitutions of Ga for Cu and Te for Sb not only cause the enhancement of power factor via electronic band structure tuning, but also leads to a drop in both the electronic and lattice thermal conductivities. As a result, the total thermal conductivity (κ) decreases to 0.98 W m−1 K−1 at 770 K, which is about 58% that of the pristine CSS, thus improving the TE performance with the highest dimensionless figure of merit value increasing to 0.95 for (Cu12Sb4S13)0.9(Ga2Te3)0.1 at 773 K, 1.9 times that of the pristine CSS (≈0.5 at 770 K).

Effect of Ni-doping on the structural and electronic properties of metal halide perovskite CsSnBr3: a DFT study

The structural and electronic properties of pure and Ni-doped perovskite CsSnBr3 in unit cell and supercell were computed using density functional theory at ambient pressure. Computed formation energy values of undoped and Ni-doped CsSnBr3 compounds show that these structures are stable. We used both standard DFT and HSE06 calculation in electronic band structure of pure and Ni-doped CsSnBr3 compounds. Since the band gap of undoped and Ni-doped CsSnBr3 compounds is located at the R symmetry point in the Brilloun zone, these compounds are materials with a direct band gap. In the HSE06 calculation, it was found that the band gap of 12.5% Ni doped-CsSnBr3 increased significantly from 1.1162 eV to 1.4343 eV. The electron charge density, Bader charge analysis and density of states reveal a strong covalent bond between Sn-Br (Ni-Br) and a strong ionic bond between Cs-Br. The direct electronic band gaps of undoped and Ni-doped CsSnBr3 perovskites in the visible energy range show that these compounds can be used effectively in optical applications.

Modular Assembly of Metamaterials Using Light Gradients.

This is a report on a pilot study that tests the feasibility of assembling photonic metamaterials (PMs) using light gradient forces. Following a strategy that works like modular construction, light gradient forces, produced by a tightly focused, one-dimensional standing wave optical trap (SWOT), time-multiplexed across a two-dimensional lattice were used to assemble voxels consisting of prefabricated, monodispersed nanoparticles (NPs) with radii ranging from 30 to 500nm into three-dimensional structures on a hydrogel scaffold. Hundreds of NPs can be manipulated concurrently into a complex heterogeneous voxel this way, and then the process can be repeated by stitching together voxels to form a metamaterial of any size, shape, and constituency although imperfectly. Imperfections introduce random phase-shifts and amplitude variations that can have an adverse effect on the band structure. Regardless, PMs were created this way using two different dielectric NPs, polystyrene and rutile, and then the near-infrared performance for each was analyzed with angle-, wavelength-, and polarization-dependent reflection spectroscopy. The cross-polarized spectra showed evidence of a resonance peak. Interestingly, whereas the line-shape from the polypropylene array was symmetric, the rutile array was not, which may be indicative of Fano resonance. So, even with the structural defects, reflection spectroscopy revealed a resonance. This article is protected by copyright. All rights reserved.

Direct Z‐Scheme Heterostructure of Nanoparticle‐CdSe on Nanorod‐NaNbO3: Facile Hydro‐thermal Construction and Superior Photocatalytic Activity and Stability in H2 Evolution

AbstractThe advancement of exceptionally effective catalysts that are photostable is significantly important for the sustainable conversion of solar energy into hydrogen. Combining the strengths of NaNbO3 and CdSe in a fabricated heterojunction has been pursued in photocatalysis to enhance the performance while addressing CdSe′s stability. In this study, nanoparticle‐CdSe was deposited on NaNbO3 nanorods via hydrothermal method, and the optimal composite ratio of CdSe/NaNbO3 heterojunction achieved a photocatalytic hydrogen production of 2510 μmol g−1h−1. The enhancement is ascribed to the formation of a Z‐scheme heterojunction by the interface contact between CdSe and NaNbO3.The migration of electrons from NaNbO3 to CdSe was revealed by charge density difference results in DFT calculation. Work function of samples demonstrated the equilibrium of Fermi level and a corresponding shift of the band structure in the heterojunction. The H adsorption free energy (ΔGH*) for the heterojunction was 0.26 eV, suggesting a reduced energy barrier for hydrogen generation. Notably, the stable structure of NaNbO3 endows the composites with excellent chemical stability, maintaining more than 80 % activity after six hydrogen production cyclic tests. This work offers valuable insights into the development of direct Z‐scheme structure catalysts for photocatalytic water splitting.

Estimation of Maximum <i>zT</i> in Cu<sub>3</sub>SbSe<sub>4</sub> for Different Starting Materials Content

Cu<sub>3</sub>SbSe<sub>4</sub> is considered a promising thermoelectric material because of its large effective mass and low thermal conductivity, originating from its unique lattice structure. However, Cu<sub>3</sub>SbSe<sub>4</sub> has intrinsically low carrier concentration and relatively high electric resistance which limit performance. Recently, a <i>zT</i> improvement in Cu<sub>3</sub>SbSe<sub>4</sub> was reported where doping/precipitation is controlled by changing the content of the starting materials. However, the effect of these changes in starting content on electronic band structures has not been studied. Here, we investigate how the change in starting materials content (<i>x</i> varying from 6 to 20) affects band parameters like density-of-states effective mass (<i>m<sub>d</sub></i> *), non-degenerate mobility (<i>μ<sub>0</sub></i>), weighted mobility (<i>μ<sub>W</sub></i>), and B-factor using the Single Parabolic Band (SPB) model. For <i>x</i> greater than 8, precipitation of the secondary phase (CuSe) was observed, and the band parameters changed differently for <i>x</i> greater than 8. The <i>m<sub>d</sub></i> * increases up to <i>x</i> = 8 and then rapidly decreases for <i>x</i> > 8. For <i>μ<sub>0</sub></i>, an overall decrease is observed for increasing <i>x</i>, but the rate of decrease is suppressed for <i>x</i> > 8. The <i>μ<sub>W</sub></i> reaches the maximum at <i>x</i> = 8. As <i>x</i> increases, the experimental lattice thermal conductivity also increases, especially for <i>x</i> > 8. Therefore, the B-factor, which is directly related to the theoretical maximum zT, becomes maximum at = 8. Hence the SPB model predicts a maximum <i>zT</i> of 0.0484 for <i>x</i> = 8 at 300 K, which is 15.5% higher than the experimental <i>zT</i> of 0.0419, which can be achieved by tuning the Hall carrier concentration to 4.44 × 10<sup>19</sup> cm<sup>-3</sup>.

Biotemplated Fe/La-co-doped TiO2 for photocatalytic depth treatment of compressed leachate from refuse transfer station.

Compressed leachate is a contaminated liquid containing various organic and inorganic pollutants produced in municipal refuse transfer stations, which pollute soil and groundwater, posing serious risks to the environment and human health. The Environmental Technology Co., Ltd. (Shenzhen, Guangdong Province, South China) treated compressed leachate obtained from a refuse transfer station. The chemical oxygen demand (COD) (641.2mg/L) of treated compressed leachate did not meet the wastewater quality standards in China for discharge into municipal sewers (COD ≤ 500mg/L) and the company's design discharge requirements (COD ≤ 400mg/L). Therefore, their further in-depth treatment is necessary. To this end, waste tobacco leaves were used as the biotemplate herein, and Fe/La-co-doped TiO2 (xFe,yLa)-TTiO2(g) was synthesized using a solvothermal-assisted biotemplating method. The photocatalytic depth treatment of compressed leachate was performed under simulated solar light using the prepared catalysts. After (3Fe,3La)-TTiO2(g) treatment, the COD of the leachate decreased from 641.2 to 280.1mg/L, and the COD removal rate was 1.2, 1.1, and 1.6 times higher than that of pure Fe-doped, La-doped and non-biological template TiO2, respectively. Characterization confirmed that the biological template endowed the catalyst with a unique morphology and high specific surface area. Its rich activity sites are conducive to enhancing the adsorption capacity of pollutants and providing an ideal place for photocatalytic reactions. Co-doping with iron and lanthanum ions altered the band structure of TiO2 and promoted the interconversion of Fe3+/Fe2+ and La3+/La2+ during photocatalysis. First-principles density functional theory simulations demonstrated that co-doping Fe and La in TiO2 created impurity levels that facilitated the transfer of photogenerated electrons. This study provides a new purification pathway for the depth treatment of compressed leachate.

Observation of 2D-magnesium-intercalated gallium nitride superlattices.

Sincethe demonstration of p-type gallium nitride (GaN) through doping with substitutional magnesium (Mg)atoms1,2, rapid and comprehensive developments, such as blue light-emitting diodes, haveconsiderablyshaped our modern livesand contributed to a more carbon-neutral society3-5. However, the details of the interplay between GaN and Mg have remained largely unknown6-11. Here we observe that Mg-intercalated GaN superlattices can form spontaneously by annealing a metallic Mg film on GaN at atmospheric pressure. To our knowledge, this marks the first instance of a two-dimensional metal intercalated into a bulk semiconductor, with each Mg monolayer being intricately inserted between several monolayers of hexagonal GaN. Characterized as an interstitial intercalation, this process induces substantial uniaxial compressive strain perpendicular to the interstitial layers. Consequently, the GaN layers in theMg-intercalated GaN superlattices exhibit an exceptional elastic strain exceeding -10% (equivalent to a stress of more than 20 GPa), among the highest recorded for thin-film materials12. The strain alters the electronic band structure and greatly enhances hole transport along the compression direction. Furthermore, the Mg sheets induce a unique periodic transition in GaN polarity, generating polarization-field-induced net charges. These characteristics offer fresh insights into semiconductor doping and conductivity enhancement, as well as into elastic strain engineering of nanomaterials and metal-semiconductor superlattices13.

Transport properties in ABC-ABA-ABC trilayer graphene junctions

Trilayer graphene (TLG) consists of three layers of graphene arranged in a particular stacking order. In the case of ABC-ABA-ABC stacking, the layers are arranged in an A-B-C sequence, followed by an A-B-A sequence, and again an A-B-C sequence. This stacking arrangement introduces specific electronic properties and band structures due to the different stacking configurations. We focus on elucidating the transport properties of a p-n-p junction formed with ABC-ABA-ABC stacking TLG. Employing the transfer matrix method and considering continuity conditions at the junction boundaries, we establish transmission and reflection probabilities, along with conductance. Notably, electron transport through the ABC-ABA-ABC junction exhibits Klein tunneling, resulting in substantial conductance even in the absence of a potential barrier V 0. This effect arises from the effective barrier induced by our specific stacking, facilitating the passage of a maximal number of electrons. However, the presence of V 0 diminishes Klein tunneling, leading to conductance minima. Furthermore, our findings highlight that interlayer bias δ induces a hybridization of the linear and parabolic bands of ABA-TLG within the junction, reducing resonances. In cases where δ ≠ 0 and V 0 ≠ 0, we observe a suppression of the gap, contrary to the results obtained in ABC tunneling studies where a gap exists.

Geometrical, Electronic, and Optical Properties of Rhombohedral B6O from First‐Principles Calculation

The first‐principles computational methods based on density functional theory are used to study B6O, including its structural, elastic, electronic, and optical properties. The results show that the obtained structural and mechanical parameters are in good agreement with the experimental values. The elastic constants, bulk modulus, shear modulus, Young's modulus, Poisson's ratio, and mechanical stability of rhombohedral B6O are studied. The results show that B6O has mechanical stability, anisotropy, and brittleness. The electronic structure of B6O is analyzed by band structure and density of states. Besides, the chemical bond is systematically explained in terms of Mulliken population and charge density. Finally, the optical characteristics of B6O are examined, encompassing aspects such as the complex dielectric function, conductivity, reflectivity, refractive index, absorption spectrum, and loss function.

Quasi-localization and Wannier obstruction in partially flat bands

The localized nature of a flat band is understood by the existence of a compact localized eigenstate. However, the localization properties of a partially flat band, ubiquitous in surface modes of topological semimetals, have been unknown. We show that the partially flat band is characterized by a non-normalizable quasi-compact localized state (Q-CLS), which is compactly localized along several directions but extended in at least one direction. The partially flat band develops at momenta where normalizable Bloch wave functions can be obtained from a linear combination of the non-normalizable Q-CLSs. Outside this momentum region, a ghost flat band, unseen from the band structure, is introduced based on a counting argument. Then, we demonstrate that the Wannier function corresponding to the partially flat band exhibits an algebraic decay behavior. Namely, one can have the Wannier obstruction in a band with a vanishing Chern number if it is partially flat. Finally, we develop the construction scheme of a tight-binding model for a topological semimetal by designing a Q-CLS.

Universality of optoelectronic and thermoelectric properties of novel two-dimensional CrSiM2N (M=As, P and N[dbnd]Se, Te) monolayers and their vdWHs with MoTe2

In this study, we introduce a novel two-dimensional (2D) monolayer of CrSiM2N (M = As, P and NSe, Te) and explore its electronic properties. For the first time, we employ density functional theory and investigate the electronic and thermoelectric (TE) properties of CrSiM2N (M = As, P and NSe, Te) monolayers. Our calculated phonon band structure confirms that these monolayers are stable and can potentially be synthesized experimentally. The CrSiM2N (M = As, P and NSe, Te) monolayers exhibit an indirect band nature, with the CBM and VBM located at the K and G-points of the first Brillouin zone, respectively. We have also calculated the thermoelectric properties of these systems, which suggest that these monolayers could play a crucial role in enhancing the thermoelectric performance. Furthermore, we investigated the electronic, optical and thermoelectric properties of CrSiM2N (M = As, P and NSe, Te) and MoTe2 van der Waals heterostructures (vdWHs). The electronic band structure exhibits an indirect semiconductor nature, with the conduction band maxima and valence band minima originating from the CrSiM2N (M = As, P and NSe, Te) and MoTe2 monolayers, thereby confirming a type II band alignment. The optical properties indicate that these vdWHs can absorb a broad range of light, from the ultraviolet to the visible and infrared regions. We demonstrated that CrSiM2N (M = As, P and NSe, Te) monolayers exhibit p-type TE behavior, while their vdWHs counterparts exhibit n-type TE behavior.

Potassium doping of vertically aligned multi-walled carbon nanotubes.

Alkali metal doping of multi-walled carbon nanotubes is of great interest, both fundamentally to explore the effect of dopants on quasi-one-dimensional electrical systems and for energy applications such as alkali metal storage. We present an investigation with complementary photoemission and Raman spectroscopies, fully carried out in an ultra-high vacuum, to unveil the electronic and vibrational response of a forest of highly aligned multi-walled carbon nanotubes by in situ potassium doping. The charge donation by the alkali adatoms induces a plasmon mode, and the density of states undergoes an energy shift consistent with electron donation and band filling of the multi-walled carbon nanotube band structure. The π-states in the valence band and the Raman peaks unveil an evolution that can be ascribed to charge donation and partially to a tensile strain exerted by the K adatoms on the carbon lattice. All these effects are thermally reversible, fostering these materials as a potential system for electronic charge harvesting.

Structure, Characterizations, Photocurrent Response, and Theoretical Study of One Chained Hybrid Iodoplumbate

AbstractExploring new haloplumbate hybrids and understanding the structure‐activity relationships are of great significance for further promoting their applications in the photovoltaic fields. Herein, with the in situ‐formed [Hmd]+ (md = 2‐methyl‐1,3‐diazinane) templates, a new organic–inorganic hybrid iodoplumbate, namely [Hmd]PbI3 (1), is successfully constructed and then structurally characterized using multiple technical approaches. X‐ray crystallography studies show that compound 1 features the typical 1D chain‐like motifs of [Pb2I6]n2n−, generating the 3D supermolecular network by the extensive hydrogen bond interactions. Interestingly, compound 1 exhibits the semiconductive behavior, with an optical band gap of 2.72 eV. More attractively, the title compound has good photoelectric switching performances under the alternating light irradiation, whose photocurrent densities compete well with or surpass those of many metal halide counterparts. Further theoretical analyses reveal that the title compound has a more dispersive band structure (especially the value band) that facilitates the transport of charge carriers, which may be the main origin of its excellent optoelectronic performance. Presented in this paper also bring the studies of Hirshfeld surface, X‐ray photoelectron spectroscopy (XPS) as well as thermogravimetric analysis.

Structural and electronic properties of AlGaN nanowires modulated by Al component and sectional size: A first principles study with DFT+U method

AlGaN nanowires have plenty of applications in optoelectronic functional devices. However, the electronic characteristics and stability of AlGaN nanowires are rarely explored, especially for an actual prediction of bandgaps with varying Al components. In this work, we utilize first principles calculation with DFT + U method to study the stability, charge redistribution, band structures, density of states of AlxGa1-xN alloy nanowires with x spanning from 0 to 1. The results indicate that the stability of the nanowire is enhanced with increasing nanowire diameter and Al component. The bond length in the outermost layer, vertical to the specified direction, is stretched as the Al component increases. The bandgap of nanowire is larger than that of bulk phase and the bowing parameter of nanowire is relatively low. According to the analysis of density of states (DOS), the migration of band structures is attributed to N-p states at VBM and Ga-s and Al-p states at CBM. The calculation of Crystal Orbital Hamilton Population (COHP) reveals the variation of bandgap with changing Al component and diameter. According to the analysis of electron density difference and charge transfer, Al atom has a stronger electron negativity and the electron density surrounding Ga is more delocalized compared Al atom. The results obtained in this study is expected to give some guidance for the preparation of optoelectronic devices based on AlGaN nanowires.

Simultaneous Emerging Contaminant Removal and H2O2 Generation Through Electron Transfer Carrier Effect of Bi─O─Ce Bond Bridge Without External Energy Consumption.

Conventional advanced oxidation processes (AOPs) require significant external energy consumption to eliminate emerging contaminants (ECs) with stable structures. Herein, a catalyst consisting of nanocube BiCeO particles (BCO-NCs) prepared by an impregnation-hydrothermal process is reported for the first time, which is used for removing ECs without light/electricity or any other external energy input in water and simultaneous in situ generation of H2O2. A series of characterizations and experiments reveal that dual reaction centers (DRC) which are similar to the valence band/conducting band structure are formed on the surface of BCO-NCs. Under natural conditions without any external energy consumption, the BCO-NCs self-purification system can remove more than 80% of ECs within 30min, and complete removal of ECs within 30min in the presence of abundant electron acceptors, the corresponding second-order kinetic constant is increased to 3.62 times. It is found that O2 can capture electrons from ECs through the Bi─O─Ce bond bridge during the reaction process, leading to the in situ production of H2O2. This work will be a key advance in reducing energy consumption for deep wastewater treatment and generating important chemical raw materials.

Platinum-Particle-Assisted Etching of Low-, Moderately-, and Highly-Doped p-Type Silicon: Change of Composite Porous Structure

Metal-assisted etching (metal-assisted chemical etching) is an efficient method to fabricate porous silicon (Si). When using platinum (Pt) particles as metal catalysts in metal-assisted etching, a composite porous structure of straight macropores formed beneath the Pt particles and a mesoporous layer formed on the entire surface of Si can be fabricated. The formation mechanism of the composite structure is still open to discussion. We previously demonstrated that the ratio of mesoporous layer thickness to macropore depth showed a large value (approximately 1.1) in the case of highly-doped p-Si. In this study, we investigated the composite structure formation by using p-Si substrates with different doping densities and etching solutions with different concentrations of hydrogen peroxide (H2O2). There was not significant difference in the structures formed on low- and moderately-doped Si, despite the large difference in doping density. The ratio of mesoporous layer thickness to macropore depth increased within the range approximately from 0.1 to 0.4 with increasing the H2O2 concentration in the case of low- and moderately-doped Si, but it did not change in the case of highly-doped Si. We discussed the observation results based on the spatial distribution of hole consumption and the band structures at Pt/Si and Si/electrolyte interfaces.