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Lead‐free metal halide perovskites can potentially be air‐ and water‐stable photocatalysts for organic synthesis, but there are limited studies on them for this application. Separately, machine learning (ML), a critical subfield of artificial intelligence, has played a pivotal role in identifying correlations and formulating predictions based on extensive datasets. Herein, an iterative workflow by incorporating high‐throughput experimental data with ML to discover new lead‐free metal halide perovskite photocatalysts for the aerobic oxidation of styrene is described. Through six rounds of ML optimization guided by SHapley Additive exPlanations (SHAP) analysis, BA2CsAg0.95Na0.05BiBr7 as a photocatalyst that afforded an 80% yield of benzoic acid under the standard conditions is identified, which is a 13‐fold improvement compared to the 6% with when using Cs2AgBiBr6 as the initial photocatalyst benchmark that is started. BA2CsAg0.95Na0.05BiBr7 can tolerate various functional groups with 22 styrene derivatives, highlighting the generality of the photocatalytic properties demonstrated. Radical scavenging studies and density functional theory calculations revealed that the formation of the reactive oxygen species superoxide and singlet oxygen in the presence of BA2CsAg0.95Na0.05BiBr7 are critical for photocatalysis. [ABSTRACT FROM AUTHOR]

The production of hydrogen (H2) through photoelectrochemical water splitting (PEC-WS) using renewable energy sources, particularly solar light, has been considered a promising solution for global energy and environmental challenges. In the field of hydrogen-scarce regions, metal oxide semiconductors have been extensively researched as photocathodes. For UV-visible light-driven PEC-WS, cupric oxide (CuO) has emerged as a suitable photocathode. However, the stability of the photocathode (CuO) against photo-corrosion is crucial in developing CuO-based PEC cells. This study reports a stable and effective CuO and graphene-incorporated (Gra-COOH) CuO nanocomposite photocathode through a sol-gel solution-based technique via spin coating. Incorporating graphene into the CuO nanocomposite photocathode resulted in higher stability and an increase in photocurrent compared to bare CuO photocathode electrodes. Compared to cuprous oxide (Cu2O), the CuO photocathode was more identical and thermally stable during PEC-WS due to its high oxidation number. Additionally, the CuO:Gra-COOH nanocomposite photocathode exhibited a H2 evolution of approximately 9.3 µmol, indicating its potential as a stable and effective photocathode for PEC-WS. The enhanced electrical properties of the CuO:Gra-COOH nanocomposite exemplify its potential for use as a charge-transport layer. [ABSTRACT FROM AUTHOR]

Intensive research in electrochemical CO2 reduction reaction has resulted in the discovery of numerous high-performance catalysts selective to multi-carbon products, with most of these catalysts still being purely transition metal based. Herein, we present high and stable multi-carbon products selectivity of up to 76.6% across a wide potential range of 1 V on histidine-functionalised Cu. In-situ Raman and density functional theory calculations revealed alternative reaction pathways that involve direct interactions between adsorbed histidine and CO2 reduction intermediates at more cathodic potentials. Strikingly, we found that the yield of multi-carbon products is closely correlated to the surface charge on the catalyst surface, quantified by a pulsed voltammetry-based technique which proved reliable even at very cathodic potentials. We ascribe the surface charge to the population density of adsorbed species on the catalyst surface, which may be exploited as a powerful tool to explain CO2 reduction activity and as a proxy for future catalyst discovery, including organic-inorganic hybrids. Tuning CO2 electrocatalysis to achieve multi-carbon products is interesting yet challenging. Here the authors report a histidine-functionalized Cu catalyst for CO2 reduction to multi-carbon products and reveal the correlation between catalyst surface charge and catalytic performance. [ABSTRACT FROM AUTHOR]

Combining high‐throughput experiments with machine learning accelerates materials and process optimization toward user‐specified target properties. In this study, a rapid machine learning‐driven automated flow mixing setup with a high‐throughput drop‐casting system is introduced for thin film preparation, followed by fast characterization of proxy optical and target electrical properties that completes one cycle of learning with 160 unique samples in a single day, a >10× improvement relative to quantified, manual‐controlled baseline. Regio‐regular poly‐3‐hexylthiophene is combined with various types of carbon nanotubes, to identify the optimum composition and synthesis conditions to realize electrical conductivities as high as state‐of‐the‐art 1000 S cm−1. The results are subsequently verified and explained using offline high‐fidelity experiments. Graph‐based model selection strategies with classical regression that optimize among multi‐fidelity noisy input‐output measurements are introduced. These strategies present a robust machine‐learning driven high‐throughput experimental scheme that can be effectively applied to understand, optimize, and design new materials and composites. [ABSTRACT FROM AUTHOR]

Perovskite solar cells (PSCs) have emerged recently as promising candidates for next generation photovoltaics and have reached power conversion efficiencies of 25.2%. Among the various methods to advance solar cell technologies, the implementation of nanoparticles with plasmonic effects is an alternative way for photon and charge carrier management. Surface plasmons at the interfaces or surfaces of sophisticated metal nanostructures are able to interact with electromagnetic radiation. The properties of surface plasmons can be tuned specifically by controlling the shape, size, and dielectric environment of the metal nanostructures. Thus, incorporating metallic nanostructures in solar cells is reported as a possible strategy to explore the enhancement of energy conversion efficiency mainly in semi‐transparent solar cells. One particularly interesting option is PSCs with plasmonic structures enable thinner photovoltaic absorber layers without compromising their thickness while maintaining a high light harvest. In this Review, the effects of plasmonic nanostructures in electron transport material, perovskite absorbers, the hole transport material, as well as enhancement of effective refractive index of the medium and the resulting solar cell performance are presented. Aside from providing general considerations and a review of plasmonic nanostructures, the current efforts to introduce these plasmonic structures into semi‐transparent solar cells are outlined. [ABSTRACT FROM AUTHOR]

Rational design of multi-compositional hierarchical nanostructures from earth-abundant materials holds great potential in the fields of electrocatalytic hydrogen evolution and supercapacitive energy storage. However, such nanostructures often require multi-step synthesis routes which are rather elaborate. In this study, we demonstrate a facile synthesis route to attain hierarchical nanostructures comprised of multiple constituents with varied geometric dimensionality, i.e. NiO nanoparticles incorporated in two-dimensional (2D) sulfurized molybdenum-based nanosheets coated on a one-dimensional (1D) Ni3S2 nanorod scaffold grown directly on Ni foam. The metallic nature of the Ni3S2 nanorods provides a 1D conductive pathway to the active sites, and their overall nanostructure increases the specific surface area of the electrode and maintains the structural integrity. Furthermore, synergistic interactions between the molybdenum-based nanosheets and NiO nanoparticles can improve the overall activity of the catalyst towards the hydrogen evolution reaction (HER) via playing specific roles in the water dissociation and hydrogen adsorption steps. Consequently, the design of the multi-compositional hierarchical nanostructure led to a remarkable enhancement in electrocatalytic hydrogen evolution performance, and this material also exhibited excellent supercapacitive energy storage properties. This work illustrates a straightforward approach to the design and tailoring of hierarchical nanostructured materials with promising application in the field of energy conversion and storage. [ABSTRACT FROM AUTHOR]

Photocatalysts based on p–n junction heterostructures have demonstrated their ability to enhance the separation of photo-generated charge carriers and promote their lifetimes for photocatalytic hydrogen evolution. However, few reported studies have extended to the optimization of charge carrier dynamics to facilitate favorable kinetics of the target surface reaction for photocatalysis. Herein, a novel ternary chalcogenide photocatalyst ZnMoS4 is developed with ideal multiple heterojunctions of the ZnMoS4/ZnO/CuS band structure. Besides synergistically enhancing charge carrier separation, more importantly, the intercalated ZnO layer in the ZnMoS4/CuS p–n heterojunction induces interfacial band bending that consequently allows kinetically desirable electron migration from ZnMoS4 across the multi-junction heterostructures, towards the photocatalyst surface for an efficient water reduction reaction. This optimized electrodynamic configuration results in a 97% higher hydrogen evolution rate as compared to a typical unoptimized ZnMoS4/CuS p–n heterostructure. Essentially, this work offers a band structure engineering strategy for heterostructured photocatalyst design which enables efficient charge carrier dynamics and electrochemical reactivity. [ABSTRACT FROM AUTHOR]

In this paper, we present an l-cysteine-mediated hydrothermal synthesis of manganese copper sulfide (MCS) nanocomposites with versatile nanostructures and demonstrate their applications in photocatalytic and electrocatalytic hydrogen generation from water splitting. Variation of the Mn/Cu molar ratios in the precursors facilely tailors the MCS nanocomposites into one-dimensional nanowires or two-dimensional nanosheets, which are different from the zero-dimensional nanoparticles of pure MnS and CuS. By virtue of the well-interfaced heterojunctions formed, the recombination of photogenerated electrons and holes is suppressed, giving rise to photocatalytic hydrogen generation behavior that is unattainable from either MnS or CuS. Moreover, the electrochemical conductivity is dramatically enhanced, rendering the MCS nanocomposites with improved electrocatalytic kinetics. This approach will contribute to an inexpensive and convenient synthetic strategy of transition-metal-based nanostructures for functional applications in photovoltaic, electrochemical, and catalytic fields. [ABSTRACT FROM AUTHOR]

Currently, the production of hierarchical 2 D layered carbon is mostly limited by low yields, laborious processing, and the high tendency for reaggregation. Hence, it is still a challenge to attain stable porous carbon structures with a well-preserved layered structure and hierarchical pores. Here, we demonstrate a facile and simultaneous activation-exfoliation-reassembly technique to perform structural modification and pore tailoring of carbonaceous matrices conveniently. Various pore creations can be realized concurrently from in-plane micro-/mesopores by chemical activation, expansion of intersheet mesopores, and interconnectivity of the layered structure to form 3 D macropores. Finally, a proof-of-concept demonstration of the combination of hierarchical macro-/micro-/mesoporous layered carbon structure and TiO2 nanosheets shows promising adsorption and catalytic properties. [ABSTRACT FROM AUTHOR]

A hybrid composite that unifies multiple structural attributes is the key for improved functional device performance. Moreover, hierarchical and porous assembly of dissimilar constituent elements at various length scales and dimensionality is highly appropriate for mass transfer and surface/interfacial-dominated reactions. Here, we demonstrate solution processed 2D-on-2D hierarchical architecture of nanobelt core–nanosheets shell consisting of dissimilar transition metal composite. The defining benefits of such hetero-structured material design are short ion diffusion pathway of a thin 2D nanobelt core that is interfaced to large surface area and porous 2D nanosheets. Accordingly, an integrated energy system that delivers multiple functionalities, i.e. supercapacitive charge storage and electrochromic optical modulation, is investigated due to its attractive complementary energy storage and energy conservation capabilities. Consequently, bifunctional electrochromism–supercapacitive properties are demonstrated where desirable optical transmittance modulation and coloration efficiency properties in parallel with favorable pseudocapacitive storage and specific capacitance properties are simultaneously realized. Such an integrated energy system is anticipated to have a broad range of smart applications in buildings, automobiles and other emerging electronics needs. [ABSTRACT FROM AUTHOR]

While electrochemical water splitting is one of the most promising methods to store electrical energy in chemical bonds, facile fabrication of transition metal electrocatalyst materials with judicious chemical and structural design to facilitate high electrochemical reactivity with an in-built gas bubble release mechanism is currently lacking. Here, a facile pseudomorphic-phase transformation of a diversified ternary NiCo hierarchical structure is demonstrated. Essentially, a universal template of hydroxide derivatives facilitates successive pseudomorphic-phase transformation with structural framework preservation. Direct growth of integrated 2D nanosheet-1D nanowire hierarchical features onto a conductive electrode leads to strong interfacial contact and an extended platform for electrolyte accessibility as well as provision of a discontinuous surface for low adhesion gas bubble evolution. Collectively, the as-prepared mixed transition metal and multi-dimensional structured electrode presents a uniquely advantageous electrochemical energy conversion material design. [ABSTRACT FROM AUTHOR]

A novel approach to enhance the photocurrent and photostability of semiconductor-sensitized photoelectrochemical cells (PECs) with a nonsacrificial electrolyte by grafting the CdS surface with a molecular relay, 4-( N, N-diphenylamino)benzoic acid (DPABA) is reported. Using this modification, the PECs are able to perform overall water splitting instead of only hydrogen generation. The probable reasons for the improvement are that the photogenerated holes in the CdS valence band could be rapidly removed by DPABA, which facilitates charge separation and thus suppresses the photocorrosion process. The use of such a method might further improve the performance of overall water splitting, together with superior light-absorption sensitizers and more suitable molecular relays with better oxygen evolution reaction catalytic properties. [ABSTRACT FROM AUTHOR]

A novel Co9S8–NixSy/Ni foam composite material was synthesized through the thermal decomposition of a cobalt–thiourea molecular precursor onto a 3D metallic support. The obtained electrode exhibited good activity toward the hydrogen evolution reaction in an alkaline medium, requiring a small overpotential of 163 mV at a current density of 10 mA cm−2, which is one of the lowest ever reported among transition metal sulfide materials. [ABSTRACT FROM AUTHOR]

Cocatalysts, when loaded onto a water splitting photocatalyst, accelerate the gas evolution reaction and improve the efficiency of the photocatalyst. In this paper, we report that the efficiency of the photocatalyst is enhanced using an amorphous cobalt oxide cocatalyst. The WO3 film, when loaded with amorphous or nanocrystalline Co3O4, shows an improvement of up to 40% in photocurrent generation and 34% in hydrogen gas evolution. The effect of cocatalyst crystallinity on performance was systematically studied, and we found that the photocurrent deteriorates with the conversion of the cocatalyst to a highly crystalline phase at an annealing temperature of 500 °C. The mechanism of this effect was studied in detail using electrochemical impedance spectroscopy, and the enhancement effect produced by the amorphous cocatalyst is attributed to the large density of unsaturated catalytically active sites in the amorphous material. [ABSTRACT FROM AUTHOR]

Porous TiO2 hierarchical spheres with high surface area synthesized via a solvothermal method were successfully modified with an Ag2S co-catalyst by a sequential ionic deposition (SID) method at room temperature. The presence of Ag2S facilitated efficient charge separation, thus reducing recombination and enhancing the photocatalytic activity of the photocatalyst. The enhanced photocatalytic performance was demonstrated by water splitting where hydrogen (H2) gas was produced at an evolution rate of 708 μmol h−1 g−1 and methyl orange was degraded with a rate constant of 0.018 min−1. This is the first time that photocatalytic water splitting using a suspension system has been demonstrated on a Ag2S/TiO2 hierarchical heterostructure and the material shows stability in its photocatalytic performance despite being recycled several times. The composite material presents properties which are highly promising for the generation of clean energy and environmental clean up applications. [ABSTRACT FROM AUTHOR]

Cu2O and CuO are attractive photocatalytic materials for water splitting due to their earth abundance and low cost. In this paper, we report the deposition of Cu2O and CuO thin films by a sol–gel spin-coating process. Sol–gel deposition has distinctive advantages such as low-cost solution processing and uniform film formation over large areas with a precise stoichiometry and thickness control. Pure-phase Cu2O and CuO films were obtained by thermal annealing at 500 °C in nitrogen and ambient air, respectively. The films were successfully incorporated as photocathodes in a photoelectrochemical (PEC) cell, achieving photocurrents of −0.28 mA cm−2 and −0.35 mA cm−2 (for Cu2O and CuO, respectively) at 0.05 V vs. a reversible hydrogen electrode (RHE). The Cu2O photocurrent was enhanced to −0.47 mA cm−2 upon incorporation of a thin layer of a NiOx co-catalyst. Preliminary stability studies indicate that CuO may be more stable than Cu2O as a photocathode for PEC water-splitting. [ABSTRACT FROM AUTHOR]

We used a bilayer field effect transistor (FET) consisting of a thin PbS nanocrystals (NCs) film interfaced with vacuum-deposited pentacene to probe trap states in NCs. We interpret the observed threshold voltage shift in context of charge carrier trapping by PbS NCs and relate the magnitude of the threshold voltage shift to the number of trapped carriers. We explored a series of NC surface ligands to modify the interface between PbS NCs and pentacene and demonstrate the impact of interface chemistry on charge carrier density and the FET mobility in a pentacene FET. [ABSTRACT FROM AUTHOR]

Considering energy band alignment and polarization effect, ferroelectric BiFeO3 thin films are proposed as the photoanode in a monolithic cell to achieve unassisted photocatalytic water splitting. Significant anodic photocurrent was observed in our epitaxial ferroelectric BiFeO3 films prepared from sputter deposition. Both negative polarization charges and thinner films were found to promote the anodic photocatalytic reaction. Ultraviolet photoelectron spectroscopy proved that the conduction and valence band edges of BiFeO3 straddle the water redox levels. Theoretical analyses show that the large switchable polarization can modify the surface properties to promote the hydrogen and oxygen evolutions on the surfaces with positive and negative polarization charges, respectively. [ABSTRACT FROM AUTHOR]

Poly(vinylidene fluoride) (PVDF) homopolymer nanotubearray with the desired ferroelectric β-phase is fabricated inan anodic alumina membrane (AAM) template. The results indicate thatthe hydrogen bonds between the AAM surface hydroxyl groups and PVDFmolecules promote the formation of the β phase. A significantlyimproved effective piezoelectric coefficient d33of −19.2 pm/V is obtained over the thin film counterpartwith a solid substrate. [ABSTRACT FROM AUTHOR]

CuO is an earth-abundant, nontoxic, and low band-gap material; hence it is an attractive candidate for application in solar cells. In this paper, a synthesis of CuO nanocrystals by a facile alcohothermal route is reported. The nanocrystals are dispersible in a solvent mixture of methanol and chloroform, thus enabling the processing of CuO by solution. A bilayer solar cell comprising of CuO nanocrystals and phenyl-C61-butyric acid methyl ester (PCBM) achieved a power conversion efficiency of 0.04%, indicating the potential of this material for light-harvesting applications. [ABSTRACT FROM AUTHOR]

Bayesian Optimization 3D visualization of Gaussian process (GP) prediction and uncertainty manifolds for a concrete compressive strength dataset, which evolved after several iterations of Bayesian optimization with a GP surrogate model. More details can be found in article 2100101 by Yee‐Fun Lim, Kedar Hippalgaonkar and co‐workers. [ABSTRACT FROM AUTHOR]

A photovoltaic ultraviolet (UV) sensor is designed with a unique structure comprising of an in-plane polarized ferroelectric lead lanthanum zirconate titanate (PLZT) thin film on a transparent silica substrate and with an interdigital electrodes on the top surface. Both the experimental measurements and theoretical analyses showed that the UV sensor exhibited significantly enhanced responses with the incident UV irradiation input from the silica substrate in comparison with that from the top surface of the PLZT film. The proposed device configuration leads to a cost-effective scratch- and moisture-proof UV sensor with a flip-chip package, which promises great robustness for UV monitoring in harsh conditions. [ABSTRACT FROM AUTHOR]

Spray deposition is emerging as an attractive low-cost and high throughput method for organic solar cell (OSC) fabrication. In this letter, we demonstrate that a highly conductive formulation of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) can be spray deposited to form the top electrode for an OSC. An inverted solar cell fabricated in this way with a blend of poly(3-hexylthiophene) and [6,6]-phenyl-C61 butyric acid methyl ester as the active layer achieved a power conversion efficiency of 2.0% under AM 1.5 100 mW/cm2 illumination. [ABSTRACT FROM AUTHOR]

Neuromorphic computing, which emulates the biological neural systems could overcome the high‐power consumption issue of conventional von‐Neumann computing. State‐of‐the‐art artificial synapses made of two‐terminal memristors, however, show variability in filament formation and limited capacity due to their inherent single presynaptic input design. Here, a memtransistor‐based artificial synapse is realized by integrating a memristor and selector transistor into a multiterminal device using monolayer polycrys‐talline‐MoS2 grown by a scalable chemical vapor deposition (CVD) process. Notably, the memtransistor offers both drain‐ and gate‐tunable nonvolatile memory functions, which efficiently emulates the long‐term potentiation/depression, spike‐amplitude, and spike‐timing‐dependent plasticity of biological synapses. Moreover, the gate tunability function that is not achievable in two‐terminal memristors, enables significant bipolar resistive states switching up to four orders‐of‐magnitude and high cycling endurance. First‐principles calculations reveal a new resistive switching mechanism driven by the diffusion of double sulfur vacancy perpendicular to the MoS2 grain boundary, leading to a conducting switching path without the need for a filament forming process. The seamless integration of multiterminal memtransistors may offer another degree‐of‐freedom to tune the synaptic plasticity by a third gate terminal for enabling complex neuromorphic learning. [ABSTRACT FROM AUTHOR]

We report transport measurements of dual gated MoS2 and WSe2 devices using atomic layer deposition grown Al2O3 as gate dielectrics. We are able to achieve current pinch-off using independent split gates and observe current steps suggesting possible carrier confinement. We also investigated the impact of gate geometry and used electrostatic potential simulations to explain the observed device physics. [ABSTRACT FROM AUTHOR]

A significant methodology gap remains in the construction of advanced electrocatalysts, which has collaborative defective functionalities and structural coherence that maximizes electrochemical redox activity, electrical conductivity, and mass transport characteristics. Here, a coordinative self‐templated pseudomorphic transformation of an interpenetrated metal organic compound network is conceptualized into a defect‐rich porous framework that delivers highly reactive and durable photo(electro)chemical energy conversion functionalities. The coordinative‐template approach enables previously inaccessible synthesis routes to rationally accomplish an interconnected porous conductive network at the microscopic level, while exposing copious unsaturated reactive sites at the atomic level without electronic or structural integrity trade‐offs. Consequently, porous framework, interconnected motifs, and engineered defects endow remarkable electrocatalytic hydrogen evolution reaction and oxygen evolution reaction activity due to intrinsically improved turnover frequency, electrochemical surface area, and charge transfer. Moreover, when the hybrid is coupled with a silicon photocathode for solar‐driven water splitting, it enables photon assisted redox reactions, improved charge separation, and enhanced carrier transport via the built‐in heterojunction and additive co‐catalyst functionality, leading to a promising photo(electro)chemical hydrogen generation performance. This work signifies a viable and generic approach to prepare other functional interconnected metal organic coordinated compounds, which can be exploited for diverse energy storage, conversion, or environmental applications. A defect‐rich porous selenide‐based framework is obtained from an interpenetrated Prussian blue analog network. The resulting structure displays an interconnected porous conductive network at the microscopic level and exposes excess reactive crystal boundary defects in the form of unsaturated atoms at the edges and interfaces at the atomic level. It delivers highly reactive and durable photo(electro)chemical energy conversion functionalities. [ABSTRACT FROM AUTHOR]

Selective laser melting (SLM) was used for additive manufacturing multi-wall carbon nanotube (MWCNT) reinforced Inconel 625 composites. The MWCNTs were coated on Inconel 625 powder through molecular-level mixing. Compared to the SLM fabricated Inconel 625 sample, the composite sample showed significant improvement in ultimate tensile and yield strength with less elongation. Heat-treatment on the composite sample recovered its elongation to the level of pure Inconel 625 while maintaining its ultimate tensile strength but reducing its yield strength. The microstructures of the composite sample had a slightly faster cooling rate than the pure metallic sample during SLM fabrication. The electron backscatter diffraction graphs revealed the grain refinement induced by MWCNTS in the alloy matrix. The Raman spectra and TEM micrographs revealed the presence of MWCNT in the metal matrix after SLM fabrication. [ABSTRACT FROM AUTHOR]

Structural properties and solar cells performance of sputter grown sub-micrometer thick (~600 nm) Cu 2 ZnSnS 4 (CZTS) films are investigated for low cost and large scale photovoltaic deployment. The CZTS films are deposited using single quaternary stoichiometric target at room temperature. X-ray diffraction, micro-Raman spectroscopy, and scanning electron microscopy measurements were carried out to investigate the structural property and secondary phase formation. The intense phonon peak at 334 cm −1 in the visible Raman spectra confirms the deposition of single phase CZTS films. CZTS-based thin film solar cells show excellent performance with open circuit voltage ~600 mV and over all cell efficiency of ~3.07%, exhibiting commercial potential toward large scale fabrication of photovoltaic devices. [ABSTRACT FROM AUTHOR]