Surface Termination Research Articles

Stability of silicon–tin alloyed nanocrystals with high tin concentration synthesized by femtosecond laser plasma in liquid media

Nanocrystals have a great potential for future materials with tunable bandgap, due to their optical properties that are related with the material used, their sizes and their surface termination. Here, we concentrate on the silicon–tin alloy for photovoltaic applications due to their bandgap, lower than bulk Si, and also the possibility to activate direct band to band transition for high tin concentration. We synthesized silicon–tin alloy nanocrystals (SiSn-NCs) with diameter of about 2–3 nm by confined plasma technique employing a femtosecond laser irradiation on amorphous silicon–tin substrate submerged in liquid media. The tin concentration is estimated to be sim 17%, being the highest Sn concentration for SiSn-NCs reported so far. Our SiSn-NCs have a well-defined zinc-blend structure and, contrary to pure tin NCs, also an excellent thermal stability comparable to highly stable silicon NCs. We demonstrate by means of high resolution synchrotron XRD analysis (SPring 8) that the SiSn-NCs remain stable from room temperature up to 400,^{circ }text {C}, with a relatively small expansion of the crystal lattice. The high thermal stability observed experimentally is rationalized by means of first-principle calculations.

Effect of surface functional groups on MXene conductivity.

We report the in-plane electron transport in the MXenes (i.e., within the MXene layers) as a function of composition using the density-functional tight-binding method, in conjunction with the non-equilibrium Green's functions technique. Our study reveals that all MXene compositions have a linear relationship between current and voltage at lower potentials, indicating their metallic character. However, the magnitude of the current at a given voltage (conductivity) has different trends among different compositions. For example, MXenes without any surface terminations (Ti3C2) exhibit higher conductivity compared to MXenes with surface functionalization. Among the MXenes with -O and -OH termination, those with -O surface termination have lower conductivity than the ones with -OH surface terminations. Interestingly, conductivity changes with the ratio of -O and -OH on the MXene surface. Our calculated I-V curves and their conductivities correlate well with transmission functions and the electronic density of states around the Fermi level. The surface composition-dependent conductivity of the MXenes provides a path to tune the in-plane conductivity for enhanced pseudocapacitive performance.

Enumeration of Subperiodic Zeolitic Tetrahedral Frameworks. III. Layers, Rods, Tubes, and Clusters

We describe a new database of 4-coordinated hypothetical “subperiodic” zeolitic frameworks, comprising 0-periodic (clusters), 1-periodic (rods and tubes), and 2-periodic (layers) structures. The structures are found by a combinatorial search over 4-coordinated directed graphs, given the space group and the number of unique tetrahedral vertices, as in our earlier database. However, the filters are now reversed to reject the 3-periodic zeolites. Being fully 4-coordinated, these subperiodic structures require no hydroxyl terminations at their free surfaces when realized as SiO2 silicates. The layers closely resemble thin zeolites and are particularly interesting candidates for synthesis. The layer structures offer a rich library of structural possibilities for low-energy termination of the free surfaces of the known zeolites while maintaining full tetrahedral coordination. We present two examples of possible (001)-surface reconstructions for the LTL framework.

Characterizing Structure-Dependent TiS2/Water Interfaces Using Deep-Neural-Network-Assisted Molecular Dynamics

As a promising layered electrode material, TiS2-based capacitive deionization (CDI) devices for water desalination have attracted significant attention. However, TiS2/H2O interfacial features, potentially important for device optimization, remain unidentified. Using Deep Potential Molecular Dynamics (DPMD), we characterized distinct aqueous interfaces introduced by four TiS2 terminations expected to be present as water intercalates into TiS2, namely, Armchair, Zigzag, Zigzag-L, and Zigzag-R. First, we assessed important representative physical properties of the system to validate the deep potentials (DPs). DPMD simulations agree well with experiments and first-principles simulations, suggesting the DPs are accurate and reliable. Subsequent simulations of these TiS2/water interfaces revealed how TiS2 surface termination influences the structure of interfacial water. This effect is most evident in the first and second water layers close to the TiS2 surface, and more pronounced when spontaneous dissociative adsorption of water occurs. The extent of water dissociation on each surface was evaluated using enhanced sampling. Zigzag-L is the only interface where proton transfer from adsorbed water to TiS2 surface S atoms is thermodynamically and kinetically favored. The coexistence of surface four-fold-coordinated Ti (Ti4c) and one-fold-coordinated S (S1c) is found to be essential to making proton transfer feasible on the Zigzag-L surface. Furthermore, remaining unprotonated S1c atoms can act as good proton acceptors after water dissociation. Thus, TiS2 with Zigzag-L termination may be a surface to avoid in CDI device construction, given that pH fluctuations adversely affect performance. This work provides new understanding of TiS2/H2O interfacial features that could aid future design and optimization of TiS2-based CDI devices for water desalination.

Changes in fundamental and catalytic properties of β-molybdenum carbide decorated by a single atom of Fe, Co, Ni and Cu

The interaction of single Fe, Co, Ni, and Cu atoms with polar terminations of orthorhombic Mo2C(001) surface has been investigated at low surface coverage by using density functional theory. Calculations indicate high stability of all considered adsorbates, regardless the surface termination. The presence of a single foreign atom has a localized impact on the properties of the surface, causing charge redistribution in the adsorbate/surface interface. As the result lowering of the work function is observed for both Mo2C(001) terminations. Another effect is shifting the position of d-band center further away from the Fermi level for surface Mo atoms of metal-terminated carbide, while no changes are seen for carbon’s near-Fermi level electronic states in the case of C-terminated modified surface. Results demonstrate a short-range effect on the stability of atomic hydrogen caused by the foreign adatom on both terminations. Specifically, the observed adsorption energy weakening would entail an enhancement in the catalytic activity of Mo2C toward hydrogen evolution reaction according to the Sabatier principle. Results evidence that molybdenum carbide modified by cobalt and iron is expected to be more active toward hydrogen evolution reaction than Mo2C modified by nickel and copper or than unmodified carbide.

Frustrating Surface Segregation by Nanoconfinement: Boosting Electrochemical Ozone Production over a B13C2-Encapsulated PtNi Alloy Electrocatalyst

A major challenge that limits the applications of nanostructured electrocatalysts is precise surface structure regulation. The critical performance-impeding factors for the important electrochemical ozone production (EOP) lie in the leaching-induced poor stability as well as the competing oxygen evolution and ozone production reactions over the most promising platinum-based electrocatalysts. Although composition diversification by alloying appears to be a prevailing strategy to optimize platinum-based electrocatalysts, a practical restriction turns out to be the inevitable surface segregation and termination of platinum-enriched structures due to their lower surface energies. In this work, we introduce the nanoconfinement of intermetallic platinum–nickel nanostructures encapsulated by boron carbide, which effectively frustrates the surface segregation of alloy nanostructures and well maintains the pristine termination of the alloy. Precise atomic-level structural elucidation and model construction of the encapsulated alloy nanostructures are achieved by quantitative electron microscopy. The composite nanoalloy with a unique surface termination evokes synergetic catalytic effects that promote the charge transfer between the surface and adsorbed oxygen intermediates, which entails outstanding EOP performance with a high Faraday efficiency of 14.8% in neutral media and long-term stability of up to 120 h as a qualified electrocatalyst for the EOP electrolyzer devices. More importantly, the current work paves a new route to overwhelm the thermodynamically limited surface structures of bare nanoalloy catalysts through diverse nanoconfinement strategies.

Surface Energies of LaMnO3 High-Index Surfaces Obtained from Density-Functional Theory

The first six cubic LaMnO3 high-index surfaces, (210), (211), (221), (310), (311), and (320), are examined for the first time. The unrelaxed and relaxed surface energies of the surfaces are computed as a function of surface model thickness using unrelaxed and relaxed surface models, respectively. The (210), (320), (211), and (221) surfaces are found to be more stable than the low-index (011) and (111) surfaces. Helping to explain this result, the surface terminations of the (210), (320), (211), or (221) surface are seen to exhibit a rotational relaxation of the MnO6 or oxygen octahedra extending from the surface into the bulk. By contrast, the relaxed surface energies of the (310) and (311) surfaces are concluded to be difficult to determine due to a structural transformation or phase change in the surface models of the surfaces away from cubic LaMnO3. The finding of a phase change is important. It indicates that a phase change in the surface models of a surface for another material could occur if the surface is relatively open and a different phase of the material is stable at low temperature. When modeling such a surface, two steps are suggested to be taken.

Towards understanding the TiO2 doping at the surface and bulk

AbstractAnatase titanium dioxide is a common photocatalyst with limited application scope due to its wide band gap energy. Valence and conduction band doping have long been used to narrow TiO2 band gap energy. The effectiveness of the process is highly dependent on the procedure adopted, and its underlying mechanism remains largely unknown. Importantly, optical changes caused by bulk doping are not always represented at the surface where the catalysis occurs. Therefore, methodologies sensitive to bulk and surface modifications are key for a holistic understanding of the doping mechanism and its effect on photocatalysis quantum yield. Herein, it is proposed the use of X‐ray absorption spectroscopy (XAS) with different probing depths to elucidate the chemical composition of bulk and surface. Soft XAS was employed to determine the chemical state of typical dopants (N and Cu) in TiO2 thin films. The XAS measurements at N K‐edge and Cu L2,3‐edge were performed in surface and bulk‐sensitive detection modes, providing direct insight into the surface‐bulk effects caused by the dopants. In the case of copper doping in the TiO2 conduction band, the data show the formation of Cu2+ in the bulk states. In contrast, the surface states are dominated by Cu+ components resulting from surface termination geometries. Moreover, X‐ray absorption spectra confirmed that the substitutional mechanism is the dominant process in Cu doping. The nitrogen doping was found to be interstitial, causing minor changes to the band structure but affecting the photoluminescence. The proposed methodology closes the gap in knowledge between materials design and photocatalytic performance by establishing atoms' disposition in bulk that affects electronic properties and on the surface that impacts the catalytic cycle.

Epitaxial growth of maghemite (001) and (111) on platinum: An ab-initio study

In this study, maghemite, the second most stable iron oxide, has been investigated using a DFT+U approach. The relative stability of the different surface terminations from the (001) and (111) planes are discussed, allowing the discrimination of preferred terminations among oxygen vs. iron, with octahedral or tetrahedral cations sites, etc. To move towards epitaxial growth of maghemite on a Pt substrate, the strain effect induced by lattice mismatch is then considered, first for isolated maghemite, then when grown on the substrate. Among bare surfaces, (001) terminations are more stable than (111) ones, strain effect significantly destabilizes (001) in contrast with (111), resulting in a change in stability. Moreover, the lower formation energy indicates that the growth of the (111) surface will be favored over the one of the (001) on the Pt substrate due to numerous Pt-O interactions. Finally, various electronic properties such as bond-lengths, bonding, charges, and density of states are analyzed to understand the nature and stability of the surfaces. For surfaces, bandgaps are smaller than bulk, with a higher deviation for (001) than for (111) surfaces.

Predicting the work function of 2D MXenes using machine-learning methods

MXenes, which are graphene-like two-dimensional transition metal carbides and nitrides, have tunable compositions and exhibit rich surface chemistry. This compositional flexibility has resulted in exquisitely tunable electronic, optical, and mechanical properties leading to the applications of MXenes in catalysis, electronics, and energy storage. The work function of MXenes is an important fundamental property that dictates the suitability of MXenes for these applications. We present a series of machine learning models to predict the work function of MXenes having generic compositions and containing surfaces terminated by O*, OH*, F*, and bare metal atoms. Our model uses the basic chemical properties of the elements constituting the MXene as features, and is trained on 275 data points from the Computational 2D Materials Database. Using 15 different features of the MXene as inputs, the neural network model predicts the work function of MXenes with a mean absolute error of 0.12 eV on the training data and 0.25 eV on the testing data. Our feature importance analysis indicates that properties of atoms terminating the MXene surface like their electronegativity, most strongly influence the work function. This sensitivity of the work function to the surface termination is also elucidated through experimental measurements on Ti3C2. We introduce reduced-order models comprising of ten-, eight-, and five-features to predict the work function. These reduced-order models exhibit easier transferability to new materials, while exhibiting a marginal increased mean average error. We demonstrate the transferability of these reduced order models to new materials, by predicting the work function of MXenes having surface terminations beyond the original training set, like Br*, Cl*, S*, N*, and NH*. Predicting electronic properties like the work function from the basic chemical properties of elements, paves the way towards rapidly identifying tailored MXenes having a targeted range of properties that are required for a specific application.

Quantum capacitance of supercapacitor electrodes based on M2C MXenes with pure -O and mixed termination: A first-principles study

MXenes have drawn great attention as potential electrode material because of the high capacitive performance. However, there are little information about the quantum capacitance (Cdiff) and surface storage charge (Q) of M2C MXene with pure -O and mixed surface termination. In this paper, density functional theory (DFT) is utilized to explore the Cdiff and Q of M2CO2 monolayers with 3d, 4d and 5d transitional metals (TM) in aqueous and ionic/organic systems. The most stable configurations for the studied systems are confirmed. Sc2CO2, Zr2CO2 and Hf2CO2 monolayers are potential cathode materials. Ti2CO2 monolayer is a potential anode material. The wide voltage has little influence on the electrode type of materials. M2CO2 monolayers gradually transfer from cathode to anode material with the weakening metallicity of transitional metal atom. M2C MXenes with mixed configuration are further explored. M2CO0.42F1.19(OH)0.39 (M = Sc, Cr, Nb, Ta) are cathode materials in aqueous system, M2CO0.42F1.19(OH)0.39 (M = Ti, V, Zr, Mo, Hf, W) are suitable for anode materials.

Investigating the effect of surface termination and thickness of MXene on the detection response of the SPR sensor using FDTD simulation

Surface plasmon resonance (SPR) is an optical-based detection technique that is of great interest in research because of its rapid detection and label-free features. Current SPR sensor development focuses on modifying the sensing surface for maximum bioreceptor and target immobilization. In this research, we proposed SPR sensor with the Kretschmann configuration modified by adding immobilization layers using a few layers of MXene (Ti3C2T2). MXene is an alternative two-dimensional material suitable for sensors because it has surface termination (T2) which active to immobilize the target. The different surface termination (T=O,OH,F) and number of MXene layers was added on the SPR sensor to obtained the optimum parameters of MXene application. Using Finite-Difference Time-Domain (FDTD) method, the SPR sensor is simulated on a different refractive index background which is assumed as the analyte. The different surface termination produces different SPR curves at the same refractive index conditions, the changes are found in the position of the SPR angle and the width of the curve. Thus, the results of surface termination variations are evaluated based on the full-width half-maximum (FWHM) of the curve which indicates the detection accuracy. Meanwhile, the optimum number of MXene layers was evaluated from the sensitivity value of the MXene-modified SPR sensor to changes in refractive index from 1.33 to 1.34. The result shows that the optimum detection performance was obtained from the application of six layers MXene with surface termination F2(Ti3C2F2). This configuration resulted a sensitivity of 150.131°/RIU and the LOD is 0.01633 RIU.

Investigation of the optical and electronic properties of functionalized Ti3C2 Mxene with halid atoms using DFT calculation

Density functional theory is used to investigate the structural, electrical, and optical properties of the pure and functionalized Ti3C2 monolayer. The results illustrated that the pristine Ti3C2 Mxene and terminated ones with halogen atoms are dynamically stable metals with no energy band gap. The calculation of the phonon band dispersion depicts that the surface terminated Ti3C2 by halids is the dynamically stable novel functionalized monolayer material. The electronic band structure and density of states investigations demonstrate that all terminated monolayer structures preserve the metallic nature of Ti3C2. The calculated Partial Density of States (PDOS) shows a negligible contribution of the Ti atoms in the high-frequency optical modes compared with C atoms, while in the low-frequency optical the largest contribution belongs to the Ti and halogen group atoms. In the visible light energy range, a discrepancy between the in-plane and out-plane properties was calculated. Because of the metallic electronic structure of pristine Ti3C2 and its functionalizations, the optical band gap is not observed for all structures. Our calculated results represent the probability of tuning the optical properties of MXene by varying the surface termination atoms.

Operando Exploring and Modulating Phase Evolution Chemistry from MAX to MXenes in Molten Salt Synthesis.

Lewis acidic molten salt method is a promising synthesis strategy for achieving MXenes with controllable surface termination from numerous MAX materials. Understanding the phase evolution chemistry during etching and post-processing is highly desirable but remains a key challenge due to the lack of suitable in-situ characterizations and the complexity of the reaction process. Herein, we introduce an operando synchrotron radiation X-ray diffraction (SRXRD) technique to unveil the phase evolution process of Nb2GaC MAX under a molten-salt ambient, proposing a controllable synthesis to achieve optimal etching through precise temperature and time adjustment. Subsequently, the phase structure of Nb2CTx MXenes is successfully tailored from hexagonal to amorphous by time-dependent persulfate oxidation. The resulting amorphous Nb2CTx with a well-patterned morphology and numerous chloride terminations exhibits highly improved specific capacity, rate capability, and long cycling for Li+ storage with a Cl-containing surface protective film. Addressing the time-related phase evolution during the entire molten salt strategy provides new insights into achieving higher efficiency and controllability in preparing MXenes and shows great potential in high-performance energy storage systems based on MXenes.

PO-02-065 CATHETER ABLATION WITH TERMINATION OF PERSISTENT ATRIAL FIBRILLATION USING SPATIOTEMPORAL DISPERSION

Several strategies of electrogram (EGM) guided catheter ablation of atrial fibrillation (AF) have been previously described. A spatiotemporal dispersion (SD) ablation strategy targeting AF drivers with very high termination rates has been reported; however, these sites have not been well characterized. The purpose of this study is to validate the prior experience with SD ablation in the persistent AF cohort and further characterize the regions of AF termination. Consecutive patients with persistent AF undergoing radiofrequency catheter ablation were included. Electroanatomic mapping of SD areas was performed during AF. Ablation was delivered initially at sites of continuous SD, followed by pulmonary vein isolation in all patients. If AF did not terminate, additional regions of intermittent SD were ablated. If AF terminated to atrial tachycardia or flutter, additional electroanatomic mapping and ablation was performed to achieve sinus rhythm. Representative EGMs at sites of continuous SD, intermittent SD, and no SD are shown in Figures 1A, 1B, and 1C, respectively. Left atrial (LA) volume and surface area, termination sites, and procedural characteristics are reported. A total of 20 consecutive patients (13 male, 67 ± 9 years) with persistent AF (median time from diagnosis 5 years) undergoing ablation were included in the study. The majority of continuous SD was seen on the anterior wall (18/20 patients) and septum (15/20 patients) and occasionally on the posterior wall (8/20 patients). 17/20 (85%) patients successfully terminated to sinus rhythm during the procedure. The majority of the termination sites were on the septum and anterior wall (12/17) with none on the posterior wall. LA volume by echocardiography was smaller in the termination group (84 vs. 105 mL, p < 0.01) and fluoroscopy use was less in the termination group (2.3 vs. 4.8 min, p = 0.03). There was no difference in ejection fraction, LA surface area, radiofrequency time, or procedure time (p = NS). A very high termination rate of persistent AF was achievable with ablation of SD regions. These regions likely represent drivers of AF and seem to localize predominantly on the septum and anterior wall of the LA, and rarely on the posterior wall. Ablation incorporating SD mapping may allow for patient-tailored approach to AF ablation.

Electrochemistry of Titanium Carbide MXenes in Supercapacitor.

Novel electrode materials are always explored to achieve better performance of supercapacitors. Titanium carbide MXenes, Ti3 C2 Tx , are one of the very promising candidates for electrode materials in supercapacitors due to their unique structural and ion storage properties as 2D materials. Their large specific surface area, adjustable functionalized surface terminals, high electrical conductivities, hydrophilicity, and high Faradaic capacitance, also known widely but confusingly as pseudocapacitance, are highly desirable for making high-performance electrodes with increased dis-/charging rates and capacities. Herein, some selective electrochemical considerations of Ti3 C2 Tx MXenes for uses in supercapacitors are critically reviewed and assessed, aiming at a better fundamental understanding of the electrochemical basics and processes in Ti3 C2 Tx MXene-based electrode materials for supercapacitor applications.

Nanoarchitecture of a Ti3C2@TiO2 Hybrid for Photocatalytic Antibiotic Degradation and Hydrogen Evolution: Stability, Kinetics, and Mechanistic Insights.

Designing of a visible-light-driven semiconductor-based heterojunction with suitable band alignment and well-defined interfacial contact is considered to be an effective strategy for the transformation of solar-to-chemical energy and environmental remediation. In this context, MXenes have received tremendous attention in the research community due to their merits of abundant derivatives, elemental composition, excellent metallic conductivity, and surface termination groups. Meanwhile, a facile synthetic strategy for MXene-derived TiO2 nanocomposites with stable framework and higher photocatalytic activity under visible-light irradiation still remains a challenge for researchers. Herein, we report a novel synthetic strategy of preparing a two-dimensional Ti3C2@TiO2 nanohybrid by a facile reflux method under acidic conditions. In this oxidation reaction, protonation of the hydroxyl terminal group of MXene creates Ti more electrophilic and susceptible to an oxidative nucleophilic addition reaction with the presence of both water and oxygen. The physicochemical properties of the nanohybrid Ti3C2@TiO2 were verified by varieties of characterization techniques. High-resolution transmission electron microscopy and X-ray photoelectron spectroscopy analysis specifically elucidated the intimate interfacial interaction between Ti3C2 and TiO2. The optimized Ti3C2@TiO2-48 h photocatalyst exhibited the highest tetracycline hydrochloride (TCH, 90% in 90 min) degradation efficiency in comparison to pristine TiO2 with a rate constant (k) of 0.02463 min-1. The major contribution of •O2- and •OH radicals throughout photocatalytic TCH degradation was confirmed by the trapping experiment. Moreover, the photocatalyst showed the highest hydrogen generation rate of 140.8 μmol h-1 along with an apparent conversion efficiency of 2.2%. The excellent photocatalytic activity of Ti3C2@TiO2 originated from the superior electrical conductivity of cocatalyst Ti3C2, which facilitated spatial photogenerated e-/h+ separation and transfer at the Ti3C2 MXene@TiO2 interface. Overall, this research work will describe a promising protocol of designing MXene-derived photocatalysts toward efficient environmental remediation and wastewater treatment applications.

Neutral Silicon Vacancy Centers in Undoped Diamond via Surface Control.

Neutral silicon vacancy centers (SiV^{0}) in diamond are promising candidates for quantum applications; however, stabilizing SiV^{0} requires high-purity, boron-doped diamond, which is not a readily available material. Here, we demonstrate an alternative approach via chemical control of the diamond surface. We use low-damage chemical processing and annealing in a hydrogen environment to realize reversible and highly stable charge state tuning in undoped diamond. The resulting SiV^{0} centers display optically detected magnetic resonance and bulklike optical properties. Controlling the charge state tuning via surface termination offers a route for scalable technologies based on SiV^{0} centers, as well as charge state engineering of other defects.

Role of surface terminations in the chemical stability of CH3NH3PbI3 perovskite in combined light, H2O, and O2 environments: DFT/AIMD calculations and experimental validation

A deep understanding of the relationship between the surface termination of organic-inorganic metal halide perovskites and their structural degradation caused by environmental stimuli is critical for increasing the practicability of perovskite-based photovoltaic devices. In this work, the role of different surface termination on the degradation of CH3NH3PbI3 (MAPbI3) perovskite upon simultaneous exposure to water and oxygen in the presence of light is systematically investigated using density functional theory (DFT) and ab initio molecular dynamics (AIMD) simulations methods. Our results show that photogenerated electrons increase the interaction of H2O and O2 molecules on the MAPbI3 perovskite and the coexistence of H2O and O2 molecules degrade the MAPbI3 perovskite surface faster than the presence of either monomer on the surface. AIMD results indicate that the PbI2-terminated MAPbI3 surface undergoes significant structural degradation upon simultaneous exposure to light, H2O, and O2, whereas the MAI-terminated surface is stable. Furthermore, a series of MAPbI3-based perovskite solar cells (PSCs) with different concentrations of MAI precursor are fabricated, and their photovoltaic performance is studied. Our experimental results show that the PSC treated with 3 mg mL−1 of MAI has achieved a maximum PCE of 16.16% and a larger VOC of 1.02 V, with correspondingly improved stability. The finding presented here provides a strategy for improving the quality of the MAPbI3 perovskite layer and its photovoltaic performance.

Effect of surface termination on electronic and optical properties of lead-free tin-based eco-friendly perovskite solar cell: a first principal study.

The lead (Pb)-based halide perovskites have been reported to be promising materials for photovoltaic applications; however, the presence of toxic lead in them concerns the environmental and health issues. In this work, we have, therefore, studied the lead-free and non-toxic tin-based halide perovskite, CsSnI3, which is an eco-friendly material with high power conversion efficiency, thus, being a potential candidate for photovoltaic applications. We have investigated the influence of CsI and SnI2-terminated (001) surfaces on structural, electronic and optical properties of lead-free tin-based halide perovskite CsSnI3 from the first principal calculations, based on density functional theory (DFT). The calculations of electronic and optical parameters are performed under the parameterisation of PBE_Sol for exchange-correlation functions conjugated with modified- Beche-Johnshon (mBJ) exchange potential. The optimised lattice constant, the energy band structure and the density of states (DOS) have been calculated for the bulk and different terminated surface structures. The optical properties of CsSnI3 are computed in terms of the real and imaginary part of absorption coefficient, dielectric function, refractive index, conductivity, reflectivity, extinction coefficient and electron energy loss. The photovoltaic characteristics for the CsI-termination are found to be better than the bulk and SnI2-terminated surfaces. This study reveals that optical and electronic properties can be tuned by selecting proper surface termination in halide perovskite CsSnI3. The CsSnI3 surfaces exhibit semiconductor behaviour with a direct energy band gap and a high value of absorption power in the ultraviolet and visible region, rendering these inorganic halide perovskite materials important for the eco-friendly and efficient optoelectronic devices.