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Abstract Photocatalytic CO2 reduction is considered as a promising strategy for CO2 utilization and producing renewable energy, however, it remains challenge in the improvement of photocatalytic performance for wide‐band‐gap photocatalyst with controllable product selectivity. Herein, the sulfur‐doped In(OH)3 (In(OH)xSy‐z) nanocubes are developed for selective photocatalytic reduction of CO2 to CH4 under simulated light irradiation. The CH4 yield of the optimal In(OH)xSy‐1.0 can be enhanced up to 39 times and the CH4 selectivity can be regulated as high as 80.75% compared to that of pristine In(OH)3. The substitution of sulfur atoms for hydroxyl groups in In(OH)3 enhances the visible light absorption capability, and further improves the hydrophilicity behavior, which promotes the H2O dissociation into protons (H*) and accelerates the dynamic proton‐feeding CO2 hydrogenation. In situ DRIFTs and DFT calculation confirm that the non‐metal sulfur sites significantly weaken the over‐potential of the H2O oxidation and prevent the formation of ·OH radicals, enabling the stabilization of *CHO intermediates and thus facilitating CH4 production. This work highlights the promotion effect of the non‐metal doping engineering on wide‐band‐gap photocatalysts for tailoring the product selectivity in photocatalytic CO2 reduction.

Abstract Solar‐driven CO2 reduction into value‐added C2+ chemical fuels, such as C2H4, is promising in meeting the carbon‐neutral future, yet the performance is usually hindered by the high energy barrier of the C─C coupling process. Here, an efficient and stabilized Cu(I) single atoms‐modified W18O49 nanowires (Cu1/W18O49) photocatalyst with asymmetric Cu─W dual sites is reported for selective photocatalytic CO2 reduction to C2H4. The interconversion between W(V) and W(VI) in W18O49 ensures the stability of Cu(I) during the photocatalytic process. Under light irradiation, the optimal Cu1/W18O49 (3.6‐Cu1/W18O49) catalyst exhibits concurrent high activity and selectivity toward C2H4 production, reaching a corresponding yield rate of 4.9 µmol g−1 h−1 and selectivity as high as 72.8%, respectively. Combined in situ spectroscopies and computational calculations reveal that Cu(I) single atoms stabilize the *CO intermediate, and the asymmetric Cu─W dual sites effectively reduce the energy barrier for the C─C coupling of two neighboring CO intermediates, enabling the highly selective C2H4 generation from CO2 photoreduction. This work demonstrates leveraging stabilized atomically‐dispersed Cu(I) in asymmetric dual‐sites for selective CO2‐to‐C2H4 conversion and can provide new insight into photocatalytic CO2 reduction to other targeted C2+ products through rational construction of active sites for C─C coupling.

Abstract Understanding the CO2 transformation mechanism on materials is essential for the design of efficient electrocatalysts for CO2 reduction. In aconventional adsorbate evolution mechanism (AEM), the catalysts encounter multiple high‐energy barrier steps, especially CO2 activation, limiting the activity and selectivity. Here, lattice carbonate from Cu2(OH)2CO3 is revealed to be a mediator between CO2 molecules and catalyst during CO2 electroreduction by a 13C isotope labeling method, which can bypass the high energy barrier of CO2 activation and strongly enhance the performance. With the lattice carbonate mediated mechanism (LCMM), the Cu2(OH)2CO3 electrode exhibited ten‐fold faradaic efficiency and 15‐fold current density for ethylene production than the Cu2O electrode with AEM at a low overpotential. Theoretical calculations and in situ Raman spectroscopy results show that symmetric vibration of carbonate is precisely enhanced on the catalyst surface with LCMM, leading to faster electron transfer, and lower energy barriers of CO2 activation and carbon–carbon coupling. This work provides a route to develop efficient electrocatalysts for CO2 reduction based on lattice‐mediated mechanism.

Abstract Weyl semimetals (WSMs) have attracted great attentions that provide intriguing platforms for exploring fundamental physical phenomena and future topotronics applications. Despite the fact that numerous WSMs are achieved, WSMs with long‐distance distribution of Weyl points (WPs) in given material candidates remain elusive. Here, the emergence of intrinsic ferromagnetic WSMs in BaCrSe2 with the nontrivial nature explicitly confirmed by the Chern number and Fermi arc surface states analysis is theoretically demonstrated. Remarkably, unlike previous WSMs for which opposite chirality WPs are located very close to each other, the WPs of BaCrSe2 host a long‐distance distribution, as much as half of the reciprocal space vector, suggesting that the WPs are highly robust and difficult to be annihilated by perturbations. The presented results not only advance the general understanding of magnetic WSMs but also put forward potential applications in topotronics.

Abstract Current research efforts on single-atom catalysts (SACs) exclusively focus on nonmetal or transition-metal atoms as active centers, while employing main-group metal elements is seemingly excluded because their delocalized s/p-bands are prone to yield a broadened resonance for the interaction with adsorbates. Here, we use high-throughput first-principles calculations to investigate the possible incorporation of Mg, Al, and Ga to form graphene-based SACs for NO reduction reaction (NORR) toward NH3. 51 SAC candidates with different metal coordination environments have been computationally screened employing a rationally designed four-step process, yielding six SACs with high catalytic activity and NORR selectivity. The performance is rationalized by the modulation of s/p-band filling of the main-group metals. The adsorption free energy of NO is identified as an efficient descriptor for such SACs. The underlying physical mechanism is revealed and generally applicable to other main group metal SACs. These fundamental insights extend NORR SACs to main-group metal elements.

Abstract Nonsymmorphic symmetries open up horizons of exotic topological boundary states and even generalize the bulk–boundary correspondence, which, however, the third-order topological insulator in electronic materials are still unknown. Here, by means of the symmetry analysis and k · p models, we uncover the emergence of long-awaited third-order topological insulators and the wallpaper fermions in space group I4/mcm (No.140). Based on this, we present the hourglass fermion, fourfold-degenerate Dirac fermion, and Möbius fermion in the (001) surface of Tl4 XTe3 (X = Pb/Sn) with a nonsymmorphic wallpaper group p4g. Remarkably, 16 helical corner states reside on eight corners in Kramers pair, rendering the real electronic material of third-order topological insulators. More importantly, a time-reversal polarized octupole polarization is defined to uncover the nontrivial third-order topology, as is implemented by the 2nd and 3rd order Wilson loop calculations. Our results could considerably broaden the range of wallpaper fermions and lay the foundation for future experimental investigations of third-order topological insulators.

Abstract 2D spontaneous valley polarization attracts great interest both for its fundamental physics and for its potential applications in advanced information technology, but it can only be obtained from inversion asymmetric single-layer crystals, while the possibility to create 2D spontaneous valley polarization from inversion symmetric single-layer lattices remains unknown. Here, starting from inversion symmetric single-layer lattices, a general design principle for realizing 2D spontaneous valley polarization based on van der Waals interaction is mapped out. Using first-principles calculations, we further demonstrate the feasibility of this design principle in a real material of T-FeCl2. More remarkably, such design principle exhibits the additional exotic out-of-plane ferroelectricity, which could manifest many distinctive properties, for example, ferroelectricity-valley coupling and magnetoelectric coupling. The explored design-guideline and phenomena are applicable to a vast family of 2D materials. Our work not only opens up a platform for 2D valleytronic research but also promises the fundamental research of coupling physics in 2D lattices.

Abstract Anomalous valley Hall (AVH) effect is a fundamental transport phenomenon in the field of condensed-matter physics. Usually, the research on AVH effect is mainly focused on 2D lattices with ferromagnetic order. Here, by means of model analysis, we present a general design principle for realizing AVH effect in antiferromagnetic monolayers, which involves the introduction of nonuniform potentials to break of PT symmetry. Using first-principles calculations, we further demonstrate this design principle by stacking antiferromagnetic monolayer MnPSe3 on ferroelectric monolayer Sc2CO2 and achieve the AVH effect. The AVH effect can be well controlled by modulating the stacking pattern. In addition, by reversing the ferroelectric polarization of Sc2CO2 via electric field, the AVH effect in monolayer MnPSe3 can be readily switched on or off. The underlying physics are revealed in detail. Our findings open up a new direction of research on exploring AVH effect.

Valley, as a new degree of freedom for electrons, has drawn considerable attention due to its significant potential for encoding and storing information. Lifting the energy degeneracy to achieve valley polarization is necessary for realizing valleytronic devices. Here, on the basis of first-principles calculations, we show that single-layer FeCl2 exhibits a large spontaneous valley polarization (∼101 meV) arising from the broken time-reversal symmetry and spin-orbital coupling, which can be continuously tuned by varying the direction of magnetic crystalline. By employing the perturbation theory, the underlying physical mechanism is unveiled. Moreover, the coupling between valley degree of freedom and ferromagnetic order could generate a spin- and valley-polarized anomalous Hall current in the presence of the in-plane electric field, facilitating its experimental exploration and practical applications.

Abstract The intertwined ferroelectricity and band topology will enable the non-volatile control of the topological states, which is of importance for nanoelectrics with low energy costing and high response speed. Nonetheless, the principle to design such system is unclear and the feasible approach to achieve the coexistence of two parameter orders is absent. Here, we propose a general paradigm to design 2D ferroelectric topological insulators by sliding topological multilayers on the basis of first-principles calculations. Taking trilayer Bi2Te3 as a model system, we show that in the van der Waals multilayer based 2D topological insulators, the in-plane and out-of-plane ferroelectricity can be induced through a specific interlayer sliding, to enable the coexistence of ferroelectric and topological orders. The strong coupling of the order parameters renders the topological states sensitive to polarization flip, realizing non-volatile ferroelectric control of topological properties. The revealed design-guideline and ferroelectric-topological coupling not only are useful for the fundamental research of the coupled ferroelectric and topological physics in 2D lattices, but also enable innovative applications in nanodevices.

Photo-induced selective shortening strategy was developed to synthesize Au nanorods (NRs) with different aspect ratios, and in situ observation of photo-induced shortening of single Au nanorod was realized, which is helpful for understanding the relationship between SPR decay and geometric nanostructure. The as-synthesized plasmonic Pd–Au NRs exhibit efficient formic acid dehydrogenation. Very impressively, the interfacial interaction between plasmonic bimetallic nanostructures and adsorbed molecules (HCOOH) was explored in situ at the single-particle level. Significant photoluminescence (PL) quenching of Pd–Au NRs was observed when HCOOH contacted the catalyst, confirming the charge transfer between Pd–Au NRs and HCOOH molecules. Finally, we shed light on the catalytic mechanism of plasmon-induced HCOOH dehydrogenation by coupling single-particle PL measurement with finite difference time domain (FDTD) and density functional theory (DFT) calculations.

Abstract Overall water splitting to generate H2 and O2 is vital in solving energy problem. It is still a great challenge to seek efficient visible light photocatalyst to realize overall water splitting. In this work, the tetragonal zircon BiVO4 is prepared by epitaxial growth on FTO substrate and its overall water splitting reaction is studied. Under the influence of epitaxial strain, the conduction band position shifts negatively and beyond H+/H2 reduction potential (0 V vs NHE), which enables it to possess the photocatalytic hydrogen evolution activity. After loading cocatalysts, the overall water splitting (λ > 400 nm) is realized (H2: ≈65.7 µmol g−1 h−1, O2: ≈32.6 µmol g−1 h−1), and the value of solar hydrogen conversion efficiency is 0.012%. The single‐particle photoluminescence (PL) spectra and PL decay kinetics tests demonstrate the cocatalysts are beneficial to the separation and transfer of carriers. The new strategy of adjusting the band structure by strain is provided.

Efficient and low-cost degradation of ethylene has always been a difficult problem in the storage and transportation of fruits and vegetables. Although photocatalysis is considered to be a feasible and efficient solution for ethylene degradation, the low degradation ability of conventional catalysts for small non-polar molecules limits its application. TiO2 has the advantage of tunable microstructure, but it also has the defects of wide band gap and low utilization of sunlight. The surface plasmon resonance (SPR) effect of noble metals can effectively improve the visible light absorption range of catalysts, and the synergy of noble metals further enhances the photocatalytic ability. Herein, we developed a series of AuPt catalysts through the photo-deposition method. Benefited from the SPR effect and the synergy of Au and Pt, the efficiency of AuPt–TiO2 was 19.9, 4.64 and 2.42 times that of TiO2, Au–TiO2 and Pt–TiO2, and the photocatalytic degradation ability of AuPt–TiO2 was maintained in five cyclic stability tests. Meanwhile, the transient photocurrent spectra and PL spectra proved that the light absorption capacity and carrier separation efficiency of AuPt–TiO2 were enhanced. This work provides a new direction for enhancing non-polar small-molecule photodegradation of semiconductors.

Abstract Titanium dioxide is the only known material that can enable gas-phase CO2 photocatalysis in its anatase and rutile polymorphic forms. Materials engineering of polymorphism provides a useful strategy for optimizing the performance metrics of a photocatalyst. In this paper, it is shown that the less well known rhombohedral polymorph of indium sesquioxide, like its well-documented cubic polymorph, is a CO2 hydrogenation photocatalyst for the production of CH3OH and CO. Significantly, the rhombohedral polymorph exhibits higher activity, superior stability and improved selectivity towards CH3OH over CO. These gains in catalyst performance originate in the enhanced acidity and basicity of surface frustrated Lewis pairs in the rhombohedral form.

Creating and engineering the topological features of intrinsic magnets are essential for topological spintronic applications. Here, we propose a material platform to realize the switchable topological phase transition between quantum anomalous Hall (QAH) and quantum spin Hall (QSH) effects, unlike generally used magnetic doping, by strain engineering. At equilibrium lattice parameters, the QAH effect emerges in EuCd _2 As _2 quintuple layers with nonzero Chern number and chiral edge states. Accompanying a strain-engineered magnetic phase transition from out-of-plane ferromagnetic (FM) to in-plane antiferromagnetic (AFM) states, a topological phase transition is simultaneously achieved, resulting in the QSH effect, which is explicitly confirmed by nonzero spin Chern number and the emergence of gapless edge states, even without time-reversal symmetry. Remarkably, the obtained QSH effect is highly robust against the magnetic configurations, including FM and AFM configurations with both out-of-plane and in-plane directions, hereby promoting EuCd _2 As _2 as a wonderful candidate for understanding and utilizing the magnetic topological states in spintronics.

It is a consensus that the hydrogen economy has come to a standstill due to the lack of feasible hydrogen storage solutions, especially, the suitable hydrogen storage materials. In this work, the potential of a new kind of two-dimensional (2D) AXenes, Na _2 N and K _2 N, as hydrogen storage materials are evaluated by the first-principles calculations. In particular, we find that Na _2 N in T phase indicates a hydrogen storage capacity as high as 6.25 wt% with a desirable hydrogen adsorption energy of –0.167 eV per H _2 molecule and a desorption temperature of 216 K, identifying T-phase Na _2 N to be a very promising reversible hydrogen storage material. In accordance to our results, H _2 –Na _2 N interaction causes H _2 charge polarization, which is responsible for the moderate binding strength. In addition, Gibbs adsorption free energy reveals that the system will be more stable as more H _2 molecules are loaded on the surface.

Abstract Cu2O nanoparticles (NPs) enclosed with different crystal facets, namely, c‐Cu2O NPs with {100} facets, o‐Cu2O NPs with {111} facets, and t‐Cu2O NPs with both {111} and {100} facets, are prepared and their electrocatalytic properties for the reduction of CO2 to C2H4 are evaluated. It is shown that the selectivity and activity of the C2H4 production depend strongly on the crystal facets exposed in Cu2O NPs. The selectivities for the C2H4 production increases in the order, c‐Cu2O < o‐Cu2O < t‐Cu2O, (with FEC2H4 = 38%, 45%, and 59%, respectively). This study suggests that Cu2O NPs are more likely responsible for the selectivity and activity for the C2H4 production than the metallic Cu NPs produced on the surface of Cu2O NPs. This work provides a new route for enhancing the selectivity of the electrocatalytic CO2 reduction by crystal facet engineering.

Monoclinic bismuth vanadate (BiVO4) is an attractive material with which to fabricate photoanodes due to its suitable band structure and excellent photoelectrochemical (PEC) performance. However, the poor PEC stability originating from its severe photo-corrosion greatly restricts its practical applications. In this paper, pristine and Mo doped BiVO4 ceramics were prepared using the spark plasma sintering (SPS) method, and their photoelectrochemical properties as photoanodes were investigated. The as-prepared 1% Mo doped BiVO4 ceramic (Mo-BVO (C)) photoanode exhibited enhanced PEC stability compared to 1% Mo doped BiVO4 films on fluorine doped Tin Oxide (FTO) coated glass substrates (Mo-BVO). Mo-BVO (C) exhibited a photocurrent density of 0.54 mA/cm2 and remained stable for 10 h at 1.23 V vs. reversible hydrogen electrode (RHE), while the photocurrent density of the Mo-BVO decreased from 0.66 mA/cm2 to 0.11 mA/cm2 at 1.23 V vs. RHE in 4 h. The experimental results indicated that the enhanced PEC stability of the Mo-BVO (C) could be attributed to its higher crystallinity, which could effectively inhibit the dissociation of vanadium in BiVO4 during the PEC process. This work may illustrate a novel ceramic design for the improvement of the stability of BiVO4 photoanodes, and might provide a general strategy for the improvement of the PEC stability of metal oxide photoanodes.

ZnO, as an important semiconductor material, has attracted much attention due to its excellent physical properties, which can be widely used in many fields. Notably, the defects concentration and type greatly affect the intrinsic properties of ZnO. Thus, controllable adjustment of ZnO defects is particularly important for studying its photoelectric properties. In this work, we fabricated ZnO ceramics (ZnO(C)) with different defects through spark plasma sintering (SPS) process by varying sintering temperature and using reduction environment. The experimental results indicate that the changes of color and light absorption in as-prepared ZnO originate from the different kinds of defects, i.e., oxygen vacancies (VO), interstitial zinc (Zni), and Zinc vacancies (VZn). Moreover, with the increase in calcination temperature, the concentration of oxygen defects and interstitial zinc defects in the ceramics increases gradually, and the conductivity of the ceramics is also improved. However, too many defects are harmful to the photoelectrochemical properties of the ceramics, and the appropriate oxygen defects can improve the utilization of visible light.

Abstract Supported atomically dispersed metals are proving to be efficacious photocatalysts for CO2 reduction to solar fuels. While being atom efficient, they suffer from being noble, rare, and costly (Pt, Pd, Au, Ag, Rh) and lacking in long‐term stability. Herein, all of these problems are solved with the discovery that atomically dispersed Cu supported on ultrathin TiO2 nanosheets can photocatalytically reduce an aqueous solution of CO2 to CO. The atomically dispersed Cu can be recycled in a straightforward procedure when they become oxidatively deactivated. This advance bodes well for the development of a solar fuels technology founded on abundant, low‐cost, nontoxic, atomically dispersed metal photocatalysts.

Magnetic topological states have attracted significant attentions due to their intriguing quantum phenomena and potential applications in topological spintronic devices. Here, we propose a two-dimensional material NpAs monolayer as a candidate for multiple topological states accompanied with the changes of magnetic structures. Under the antiferromagnetic configuration, the long-awaited topological crystalline insulator (TCI) emerges with a nonzero mirror Chern number ${\mathcal{C}}_{\mathcal{M}}=1$ and a giant band gap of 630 meV, and remarkably a pair of gapless edge states can be tailored by rotating the magnetization directions while the TCI phase survives. Moreover, we establish the existence of quantum anomalous Hall effect and nontrivial nodal points under the ferromagnetic configuration, thereby giving rise to the mixed Weyl semimetal after adding the magnetization direction to topological classification. Our findings not only provide an ideal candidate for uncovering exotic topological characters with magnetism but also put forward potential applications in topological spintronics.

TiO2 has extensive applications in the fields of renewable energy and environmental protections such as being used as photocatalysts or electron transport layers in solar cells. To achieve highly efficient photocatalytic and photovoltaic applications, ongoing efforts are being devoted to developing novel TiO2-based material structures or compositions, in which a first-principles computational approach is playing an increasing role. In this review article, we discuss recent computational and theoretical studies of structural, energetic, electronic, and optical properties of TiO2-based nanocluster, bulk, and material interface for photocatalytic and photovoltaic applications. We conclude the review with a discussion of future research directions in the field.

Manipulating the valley degree of freedom as an information carrier has been a focused topic for both fundamental and applied research. Here, using first-principles calculations, we report the identification of monolayer CrX _2 (X = S, Se) as a novel two-dimensional valleytronic crystal. It shows large valley spin splitting in the valence band, attractive for the integration of valleytronics and spintronics. More importantly, through proximity coupling with monolayer CrCl _3 , the valley polarization in monolayer CrX _2 is achieved, which can be further engineered by stacking patterns. Also, the valley polarization in monolayer CrX _2 can be obtained via magnetically doping V and Mn. Specially for V-doped monolayer CrSe _2 , there are no impurity states in the band gap, beneficial for its practical applications. Our works thus provide not only exceptional two-dimensional valleytronic crystals but also promising ways for realizing valley polarizations in them.

Ag9(SiO4)2NO3 was prepared by a reactive flux method. The structures, morphologies, and light absorption properties were investigated. Owing to the polar crystal structure, an internal electric field can be formed inside the material, which can facilitate the photogenerated charge separation during the photocatalytic process. Based on both the wide light absorption spectra and high charge separation efficiency originated from the polarized internal electric field, Ag9(SiO4)2NO3 exhibit higher efficiency over Ag3PO4 during the degradation of organic dyes under visible light irradiation, which is expected to be a potential material for solar energy harvest and conversion.

Undoped and nitrogen-doped Bi12TiO20 materials were synthesized by urea addition sol-gel method. By adding urea, undoped, and N-doped gel-type precursors were synthesized by low-temperature dehydrolyzation. Nitrogen-doped and undoped nanocrystalline Bi12TiO20 were prepared by annealing at 600∘C for 30 minutes. From UV-Vis absorption and diffuse reflection spectrum, the absorbing band shifted from 420 to 500 nm by nitrogen doping. The bonds of Ti–N and N–O were identified by XPS spectra from the prepared materials, and the enhancement of visible light absorption was attributed to nitrogen's substitution of oxygen. Photocatalytic properties of prepared materials were characterized by the decomposition of Rhodamine B illuminated by whole spectra of 300 W Xe light. The photocatalyst Bi12TiO20−yNy (y=0.03) with N/(N+O) mole ratio about 3% shows better performance than that of heavily doped Bi12TiO20−zNz (z=0.06), undoped Bi12TiO20, and light-doped Bi12TiO20−xNx (x=0.01) photocatalysts due to its better crystalline morphology.

The structural and electronic properties of iron-fluorine (Fe-F) and iron-sulfur (Fe-S) codoped anatase TiO2 are investigated by first-principles based on density functional theory. Our results show that the formation energy of codoped system is lower than that of single-element doping, which indicates the synergic effect of codoping on the stability of the structure. Codopants introduced impurity gap states resulting in the electron transition energy reduction and thus the visible light absorption observed in the samples. It is concluded that Fe-S should be a better codoping pair because Fe-S codoping introduces extended impurity states resulting in stronger visible light absorption than that of Fe-F codoped compounds. This work gives understanding to the recent experiment and provides the evidence of choosing the more effective co-dopants in TiO2.

The origin of visible light absorption and photocatalytic activity of nonmetal doped anatase TiO2 were investigated in details in this work based on density functional theory calculations. Our results indicate that the electronegativity is of great significance in the band structures, which determines the relative positions of impurity states induced by the doping species, and further influences the optical absorption and photocatalytic activities of doped TiO2. The effect of charge balance on the electronic structure was also discussed, and it was found that the charge-balance structures may be more efficient for visible light photocatalytic activities. In addition, the edge positions of conduction band and valence band, which determine the ability of a semiconductor to transfer photoexcited electrons to species adsorbed on its surface, were predicted as well. The results may provide a reference to further experimental studies.

One-dimensional composite - nanowires were successfully fabricated by a simple microwave-assistant hydrothermal method. The successful fabrication of one-dimensional - nanowires can only be realized at pH value range of 1–5 of the starting solution. The fabricated nanowires were characterized by X-ray powder diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), UV-visible diffuse reflectance spectra (UV-Vis DRS), and photoluminescence (PL), respectively. The diameter of the nanowires varies from 30 to 100 nm; the length is a few micrometers. Methylene blue (MB) solutions were used to evaluate the visible light photocatalytic activities of the fabricated samples. Compared with , the fabricated - nanowires show enhanced efficiency in oxidization of MB under visible light.

A yellow/brown powder of (I2)n sensitized nanoporous TiO2 was obtained via an hydrolysis with TiCl4 and iodine hydrosol as raw material. I2 nanoparticles in the hydrosol were used as seeds to initiate the nucleation of a precursory TiO2 shell. The hybridized jumbles were further calcinated at different temperatures. The structure, crystallinity, morphology, and other physical-chemical properties of the samples are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), N2 adsorption-desorption isotherms measurements, and UV-vis diffuse reflectance spectroscopy (DRS). The formation mechanism of these (I2)n sensitized nanoporous TiO2 is discussed. Methylene blue solutions were used as model wastewater to evaluate the visible light photocatalytic activity of the samples. The results indicate that iodine can exist even in high-temperature calcination for iodine being encapsulated in the nanocavities inside TiO2. The degradation of methylene blue (MB) accorded with the first-order reaction model.

We report that β -InSe endowed with external strain realizes a novel three dimensional topological insulator (TI) by ab initio calculations. We predicate that the promising topological non-trivial state can be observed in an accessible temperature regime in β -InSe for its large spin–orbital band gap up to 121 meV. Specifically, unlike in previous literature where the band inversion (BI) in TIs is induced using heavy elements that have strong spin–orbital coupling (SOC), we provide a remarkable blueprint for stabilizing BI solely by mechanical deformation so that β -InSe could display BI even without considering SOC. Nevertheless, SOC is still needed to create a band gap at the crossing point by breaking the incompatibility symmetry of the inverted bands.

Photoelectrochemical (PEC) fuel cells that enable organic pollutants degradation while generating H2 are regarded as a viable approach in addressing global energy and environmental issues. Herein, an efficient PEC fuel cell is constructed using oxygen vacancy-rich BiVO4 (O[sub V]:BiVO4) as the photoanode and triethanolamine (TEOA) pollutant as the fuel. Under AM 1.5 G, this OV:BiVO4-TEOA PEC fuel cell shows an ultra-high photo-driven current density of 20.40 mA cm--2 at 1.23 V versus reversible hydrogen electrode, which is superior to most reported PEC fuel cells. The Faradic efficiency of H[sub 2] production is about 97.26%, and no CO2 is released in the anode chamber due to the strong CO2 adsorption by excess TEOA. Further integration of a Pt/C cocatalyst coated Si photocathode in the O[sub V]:BiVO4-TEOA PEC fuel cell can achieve bias-free H2 production with a current density of 10.17 mA cm--2. The experimental and theoretical calculation results reveal the importance of the robust complexation between the O[sub V]:BiVO[sub 4] photoanode and TEOA, which ensures thorough conversion of chemical energy in TEOA and high activity of the PEC fuel cell. This work will guide the design of efficient PEC fuel cells for simultaneous pollutant treatment and H2 production. [ABSTRACT FROM AUTHOR]