Accelerated Optimization of TiO2/Sb2Se3 Thin Film Solar Cells by High‐Throughput Combinatorial Approach

Sb₂Se₃, a V₂‐VI₃ compound semiconductor, has attracted extensive research attention in photovoltaics due to its non‐toxicity, low cost and earth‐abundant constituents. Herein, a combinatorial approach to optimize the performance of TiO₂/Sb₂Se₃ thin film photovoltaics is employed. By simultaneously conducting a series of experiments in parallel rather than one after another, combinatorial strategy increases experimental throughput and reduces personnel costs. Key parameters such as TiO₂ thickness, post‐annealing temperature and Sb₂Se₃ thickness are identified as 65 nm, 450 °C and 850 nm through the combinatorial approach. Finally, in combination with (NH₄)₂S back surface cleaning, TiO₂/Sb₂Se₃ solar cells with 5.6% efficiency and decent stability are obtained, showcasing the power of high‐throughput strategy for accelerating the optimization of Sb₂Se₃ photovoltaics.     

Adjusting the Anisotropy of 1D Sb2Se3 Nanostructures for Highly Efficient Photoelectrochemical Water Splitting

Sb₂Se₃ has recently spurred great interest as a promising light‐absorbing material for solar energy conversion. Sb₂Se₃ consists of 1D covalently linked nanoribbons stacked via van der Waals forces and its properties strongly depend on the crystallographic orientation. However, strategies for adjusting the anisotropy of 1D Sb₂Se₃ nanostructures are rarely investigated. Here, a novel approach is presented to fabricate 1D Sb₂Se₃ nanostructure arrays with different aspect ratios on conductive substrates by simply spin‐coating Sb‐Se solutions with different molar ratios of thioglycolic acid and ethanolamine. A relatively small proportion of thioglycolic acid induces the growth of short Sb₂Se₃ nanorod arrays with preferred orientation, leading to fast carrier transport and enhanced photocurrent. After the deposition of TiO₂ and Pt, an appropriately oriented Sb₂Se₃ nanostructure array exhibits a significantly enhanced photoelectrochemical performance; the photocurrent reaches 12.5 mA cm^?2 at 0 V versus reversible hydrogen electrode under air mass 1.5 global illumination.     

Atomically Thin Mesoporous In2O3–x/In2S3 Lateral Heterostructures Enabling Robust Broadband‐Light Photo‐Electrochemical Water Splitting

Atomically thin 2D heterostructures have opened new realms in electronic and optoelectronic devices. Herein, 2D lateral heterostructures of mesoporous In₂O_3–x/In₂S₃ atomic layers are synthesized through the in situ oxidation of In₂S₃ atomic layers by an oxygen plasma‐induced strategy. Based on experimental observations and theoretical calculations, the prolonged charge carrier lifetime and increased electron density reveal the efficient photoexcited carrier transport and separation in the In₂O_3–x/In₂S₃ layers by interfacial bonding at the atomic level. As expected, the synergistic structural and electronic modulations of the In₂O_3–x/In₂S₃ layers generate a photocurrent of 1.28 mA cm^?2 at 1.23 V versus a reversible hydrogen electrode, nearly 21 and 79 times higher than those of the In₂S₃ atomic layers and bulk counterpart, respectively. Due to the large surface area, abundant active sites, broadband‐light harvesting ability, and effective charge transport pathways, the In₂O_3–x/In₂S₃ layers build efficient pathways for photoexcited charge in the 2D semiconductive channels, expediting charge transport and kinetic processes and enhancing the robust broadband‐light photo‐electrochemical water splitting performance. This work paves new avenues for the exploration and design of atomically thin 2D lateral heterostructures toward robust photo‐electrochemical applications and solar energy utilization.     

Ultrafine Co3Se4 Nanoparticles in Nitrogen‐Doped 3D Carbon Matrix for High‐Stable and Long‐Cycle‐Life Lithium Sulfur Batteries

Lithium–sulfur batteries are a promising high energy output solution for substitution of traditional lithium ion batteries. In recent times research in this field has stepped into the exploration of practical applications. However, their applications are impeded by cycling stability and short life‐span mainly due to the notorious polysulfide shuttle effect. In this work, a multifunctional sulfur host fabricated by grafting highly conductive Co₃Se₄ nanoparticles onto the surface of an N‐doped 3D carbon matrix to inhibit the polysulfide shuttle and improve the sulfur utilization is proposed. By regulating the carbon matrix and the Co₃Se₄ distribution, N‐CN‐750@Co₃Se₄‐0.1 m with abundant polar sites is experimentally and theoretically shown to be a good LiPSs absorbent and a sulfur conversion accelerator. The S/N‐CN‐750@Co₃Se₄‐0.1 m cathode shows excellent sulfur utilization, rate performance, and cyclic durability. A prolonged cycling test of the as‐fabricated S/N‐CN‐750@Co₃Se₄‐0.1 m cathode is carried out at 0.2 C for more than 5 months which delivers a high initial capacity of 1150.3 mAh g^?1 and retains 531.0 mAh g^?1 after 800 cycles with an ultralow capacity reduction of 0.067% per cycle, maintaining Coulombic efficiency of more than 99.3%. The reaction details are characterized and analyzed by ex situ measurements. This work highly emphasizes the potential capabilities of transition‐metal selenides in lithium–sulfur batteries.     

3D‐Printed Conical Arrays of TiO2 Electrodes for Enhanced Photoelectrochemical Water Splitting

Control over the topography of semiconducting materials can lead to enhanced performances in photoelectrochemical related applications. One means of implementing this is through direct patterning of metal‐based substrates, though this is inadequately developed. Conventional techniques for patterned fabrication commonly involve technologically demanding and tedious processes. 3D printing, a form of additive fabrication, enables creation of a 3D object by deposition of successive layers of material via computer control. In this work, the feasibility of fabricating metal‐based 3D printed photoelectrodes is explored. Electrodes comprised of conical arrays are fabricated and the performance for photoelectrochemical water splitting is further enhanced by the direct growth of TiO2 nanotubes on this platform. 3D metal printing provides a flexible and versatile approach for the design and fabrication of novel electrode structures.     

Solution‐Processed TiO2 Nanoparticles as the Window Layer for CuIn(S,Se)2 Devices

As a wide‐bandgap semiconductor, titanium dioxide (TiO₂) with a porous structure has proven useful in dye‐sensitized solar cells, but its application in low‐cost, high‐efficiency inorganic photovoltaic devices based on materials such as Cu(InGa)Se₂ or Cu₂ZnSnS₄ is limited. Here, a thin film made from solution‐processed TiO₂ nanocrystals is demonstrated as an alternative to intrinsic zinc oxide (i‐ZnO) as the window layer of CuInS_xSe_1?x solar cells. The as‐synthesized, well‐dispersed, 6 nm TiO₂ nanocrystals are assembled into thin films with controllable thicknesses of 40, 80, and 160 nm. The TiO₂ nanocrystal films with thicknesses of 40 and 80 nm exhibit conversion efficiencies (6.2% and 6.33%, respectively) that are comparable to that of a layer of the typical sputtered i‐ZnO (6.42%). The conversion efficiency of the devices with a TiO₂ thickness of 160 nm decreases to 2.2%, owing to the large series resistance. A 9‐hour reaction time leads to aggregated nanoparticles with a much‐lower efficiency (2%) than that of the well‐dispersed TiO₂ nanoparticles prepared using a 15‐hour reaction time. Under optimized conditions, the champion TiO₂ nanocrystal‐film‐based device shows even higher efficiency (9.2%) than a control device employing a typical i‐ZnO film (8.6%).     

SrTiO3/Al2O3‐Graphene Electron Transport Layer for Highly Stable and Efficient Composites‐Based Perovskite Solar Cells with 20.6% Efficiency

For practical use of perovskite solar cells (PSCs) the instability issues of devices, attributed to degradation of perovskite molecules by moisture, ions migration, and thermal‐ and light‐instability, have to be solved. Herein, highly efficient and stable PSCs based on perovskite/Ag‐reduced graphene oxide (Ag‐rGO) and mesoporous Al₂O₃/graphene (mp‐AG) composites are reported. The mp‐AG composite is conductive with one‐order of magnitude higher mobility than mp‐TiO₂ and used for electron transport layer (ETL). Compared to the mp‐TiO₂ ETL based cells, the champion device based on perovskite/Ag‐rGO and SrTiO₃/mp‐AG composites shows overall a best performance (i.e., V_OC = 1.057 V, J_SC = 25.75 mA cm^?2, fill factor (FF) = 75.63%, and power conversion efficiency (PCE) = 20.58%). More importantly, the champion device without encapsulation exhibits not only remarkable thermal‐ and photostability but also long‐term stability, retaining 97–99% of the initial values of photovoltaic parameters and sustaining ≈93% of initial PCE over 300 d under ambient conditions.     

Mesoporous TiO2‐Sn/C Core‐Shell Nanowire Arrays as High‐Performance 3D Anodes for Li‐Ion Batteries

Three‐dimensional mesoporous TiO₂‐Sn/C core‐shell nanowire arrays are prepared on Ti foil as anodes for lithium‐ion batteries. Sn formed by a reduction of SnO₂ is encapsulated into TiO₂ nanowires and the carbon layer is coated onto it. For additive‐free, self‐supported anodes in Li‐ion batteries, this unique core‐shell composite structure can effectively buffer the volume change, suppress cracking, and improve the conductivity of the electrode during the discharge‐charge process, thus resulting in superior rate capability and excellent long‐term cycling stability. Specifically, the TiO₂‐Sn/C nanowire arrays display rechargeable discharge capacities of 769, 663, 365, 193, and 90 mA h g^?1 at 0.1C, 0.5C, 2C 10C, and 30C, respectively (1C = 335 mA g^?1). Furthermore, the TiO₂‐Sn/C nanowire arrays exhibit a capacity retention rate of 84.8% with a discharge capacity of over 160 mA h g^?1, even after 100 cycles at a high current rate of 10C.     

4‐Fluorophenyl 3‐nitro‐2‐pyridinesulfenate as a practical protecting agent for amino acids

We report a new protecting agent ( 1 , Npys‐OPh(pF)) for 3‐nitro‐2‐pyridine (Npy) sulfenylation of amino, hydroxy, and thiol functional groups. Several Npys phenoxides were synthesized from Npys chloride (Npys‐Cl) and phenols in the presence of base in 1‐step reaction, and their ability for Npy‐sulfenylation was evaluated. As a result, 1 was selected as a new Npy‐sulfenylation agent with advantages including improved physicochemical stability, more controllable reactivity, and easier handling than the conventional protecting agent Npys‐Cl.     

Long‐Lived,Visible‐Light‐Excited Charge Carriers of TiO2/BiVO4 Nanocomposites and their Unexpected Photoactivity for Water Splitting

Different mole ratios of TiO₂/BiVO₄ nanocomposites with effective contacts have are fabricated by putting BiVO₄ nanoparticles into the TiO₂ sol, followed by thermal treatment at 450 °C. Based on the transient‐state surface photovoltage responses and the atmosphere‐controlled steady‐state surface photovoltage spectra, it is concluded that the photogenerated charge carriers in the TiO₂/BiVO₄ nanocomposite with a proper mole ratio (5%) display much longer lifetime and higher separation than those in the BiVO₄ alone. This is responsible for the unexpected activity for photoelectrochemical oxidation of water, for photocatalytic production of H₂, and for photocatalytic degradation of phenol as a model pollutant under visible irradiation. Moreover, it is suggested that the prolonged lifetime and increased separation of photogenerated charges in the fabricated TiO₂/BiVO₄ nanocomposite is attributed to the unusual spatial transfer of visible‐excited high‐energy electrons of BiVO₄ to TiO₂. This work will provide feasible routes to synthesize visible‐light responsive nanomaterials for efficient solar utilization.     

Defect‐Engineered Ultrathin δ‐MnO2 Nanosheet Arrays as Bifunctional Electrodes for Efficient Overall Water Splitting

Recently, defect engineering has been used to intruduce half‐metallicity into selected semiconductors, thereby significantly enhancing their electrical conductivity and catalytic/electrocatalytic performance. Taking inspiration from this, we developed a novel bifunctional electrode consisting of two monolayer thick manganese dioxide (δ‐MnO₂) nanosheet arrays on a nickel foam, using a novel in‐situ method. The bifunctional electrode exposes numerous active sites for electrocatalytic rections and displays excellent electrical conductivity, resulting in strong performance for both HER and OER. Based on detailed structure analysis and density functional theory (DFT) calculations, the remarkably OER and HER activity of the bifunctional electrode can be attributed to the ultrathin δ‐MnO₂ nanosheets containing abundant oxygen vacancies lead to the formation od Mn³⁺ active sites, which give rise to half‐metallicity properties and strong H₂O adsorption. This synthetic strategy introduced here represents a new method for the development of non‐precious metal Mn‐based electrocatalysts for eddicient energy conversion.     

Novel Black BiVO4/TiO2−x Photoanode with Enhanced Photon Absorption and Charge Separation for Efficient and Stable Solar Water Splitting

Recent advances in solar water splitting by using BiVO₄ as a photoanode have greatly optimized charge carrier and reaction dynamics, but relatively wide bandgap and poor photostability are still bottlenecks. Here, an excellent photoanode of black BiVO₄@amorphous TiO_2?x to tackle both problems is reported. Its applied bias photon‐to‐current efficiency for solar water splitting is up to 2.5%, which is a new record for a single oxide photon absorber. This unique core–shell structure is fabricated by coating amorphous TiO₂ on nanoporous BiVO₄ with the aid of atomic layer deposition and further hydrogen plasma treatment at room temperature. The black BiVO₄ with moderate oxygen vacancies reveals a bandgap reduction of ≈0.3 eV and significantly enhances solar utilization, charge transport and separation simultaneously, compared with conventional BiVO₄. The amorphous layer of TiO_2?x acts as both oxygen‐evolution catalyst and protection layer, which suppresses anodic photocorrosion to stabilize black BiVO₄. This configuration of black BiVO₄@amorphous TiO_2?x may provide an effective strategy to prompt solar water splitting toward practical applications.     

β‐Cyclodextrin protected Cu nanoclusters as a novel fluorescence sensor for graphene oxide in environmental water samples

This paper proposed a simple and sensitive approach for detecting graphene oxide (GO) in a wide pH range in environmental water samples using fluorescent β‐CD protected Cu NCs based on the hydrogen‐bond interactions between GO and 6‐SH‐β‐CD. The influences of dilution ratio and pH were investigated. We found that the fluorescence quenching efficiency of Cu NCs by GO remained almost the same under pH from 4 to 10, which benefitted the monitoring of GO under different pH conditions in real samples. The fluorescence quenching mechanism was also discussed. The fluorescence of β‐CD protected Cu NCs could be quenched in the presence of GO with a lowest detection concentration of 0.1 mg·L^?1. Good linear correlations were obtained over the concentration range from 0 to 30 mg·L^?1 at different pH values (pH = 4, pH = 7 and pH = 12). In addition, this method was successfully applied to the determination of GO in real samples which presents more opportunities for application in environmental and material sciences.