Robust photothermal anti-icing/deicing via flexible CMDSP carbon nanotube films

Photothermal anti-icing/deicing technology is an environmentally friendly surface technology that can be applied to the surface of aircraft, vehicles or ships. However, it is still a huge challenge to develop a strong and stable flexible film that can efficiently convert light to heat. Here, based on a simple electrochemical method to construct a zinc oxide (ZnO) nanoneedles structure on the surface of the carbon nanotube film, a film with the function of condensed micro-droplet self-propelling (CMDSP) was successfully prepared. The prepared film has excellent light absorption capacity and high energy transfer efficiency (76.71%). The film has strong photothermal anti-icing/deicing performance. Under 4406 Lux light irradiation, even under low temperature conditions of -5 °C, the icing delay time exceeds 4 h. This novel characteristic is attributed to the CMDSP function on the surface and the ultra-fast evaporation mechanism, which can remove water droplets on the surface as quickly as possible. This function helps to design energy-saving equipment that requires high-power heating and deicing.

Enhancing the Photocatalytic Hydrogen Evolution Performance of the CsPbI3/MoS2 Heterostructure with Interfacial Defect Engineering

Developing highly efficient photocatalysts for the hydrogen evolution reaction (HER) by solar-driven water splitting is a great challenge. Here, we study the atomistic origin of interface properties and the HER performance of all-inorganic iodide perovskite β-CsPbI₃/2H-MoS₂ heterostructures with interfacial vacancy defects using first-principles calculations. Both CsI/MoS₂ and PbI₂/MoS₂ heterostructures have strong binding and dipole moment, which are enhanced by interfacial iodine vacancies (V_I). Because of the nature of type II heterojunctions, photogenerated electrons on the CsPbI₃ side are promptly transferred to the MoS₂ side where HER occurs, and sulfur vacancies (V_S) spoil this process, acting as surface traps. The formation energies of various defects are calculated by applying atomistic thermodynamics, identifying the growth conditions for promoting V_I and suppressing V_S formation. The HER performance is enhanced by forming interfaces with lower ΔG_H values for hydrogen adsorption on the MoS₂ side, suggesting PbI₂/MoS₂ with V_I to be the most promising photocatalyst.

Photovoltage memory effect in a portable Faradaic junction solar rechargeable device

Two-electrode solar rechargeable device is one of the promising technologies to address the problem of solar energy storage in large scale. However, the mechanism of dark output voltage remains unclear and the low volumetric energy density also limits its practical applications. Herein, we report that a Si/CoO_x/KBi_(aq)/MnO_x Faradaic junction device exhibits a photovoltage memory effect, that is, the dark output voltage can precisely record the value of the photovoltage in the device. To investigate the mechanism of the effect, we develop an open circuit potential method to real-time monitor the photo charge and dark discharge processes in the Faradaic junction device. This effect leads to minimized interface energy loss in the Faradaic junction device, which achieves much higher performances than the devices without the effect. Moreover, we realize a portable device with a record value of the dark volumetric energy density (∼1.89 mJ cm⁻³) among all reported two-electrode solar rechargeable devices. These results offer guidance to improve the performance of a solar rechargeable device and design other photoelectric devices for new applications.

A Faradaic junction solar rechargeable device is one of the promising technologies to address the problem of solar energy storage but the working mechanism remains unclear. Here, the authors report a photovoltage memory effect in a portable Si/CoO_x/KBi_(aq)/MnO_x Faradaic junction device.

Fabrication and Thermal Performance of 3D Copper-Mesh-Sintered Foam/Paraffin Phase Change Materials for Solar Thermal Energy Storage

Due to its large latent heat and high energy storage capacity, paraffin as one of the phase change materials (PCMs) has been widely applied in many energy-related applications in recent years. The current applications of paraffin, however, are limited by the low thermal conductivity and the leakage problem. To address these issues, we designed and fabricated form-stable composite PCMs by impregnating organic paraffin within graphite-coated copper foams. The graphite-coated copper foam was prepared by sintering multilayer copper meshes, and graphite nanoparticles were deposited on the surface of the porous copper foam. Graphite nanoparticles could directly absorb and convert solar energy into thermal energy, and the converted thermal energy was stored in the paraffin PCMs through phase change heat transfer. The graphite-coated copper foam not only effectively enhanced the thermal conductivity of paraffin PCMs, but also its porous structure and superhydrophobic surface prevented the paraffin leakage during the charging process. The experimental results showed that the composite PCMs had a thermal conductivity of 2.97 W/(m·K), and no leakage occurred during the charging and discharging process. Finally, we demonstrated the composite PCMs can be readily integrated with solar thermoelectric systems to serve as the energy sources for generating electricity by using abundant clean solar-thermal energy.

An unprecedented fully reduced {MoV 60} polyoxometalate: from an all-inorganic molecular light-absorber model to improved photoelectronic performance

Fully reduced polyoxometalates are predicted to give rise to a broad and strong absorption spectrum, suitable energy levels, and unparalleled electronic and optical properties. However, they are not available to date. Here, an unprecedented fully reduced polyoxomolybdate cluster, namely Na8[MoV 60O140(OH)28]·19H2O {MoV 60}, was successfully designed and obtained under hydrothermal conditions, which is rare and is the largest fully reduced polyoxometalate reported so far. The MoV 60 molecule describes one Keggin {ε-Mo12} encapsulated in an unprecedented {Mo24} cage, giving rise to a double truncated tetrahedron quasi-nesting architecture, which is further face-capped by another four {Mo6} tripods. Its crystalline stability in air, solvent tolerance, and photosensitivity were all shown. As a cheap and robust molecular light-absorber model possessing wide light absorption, MoV 60 was applied to build a co-sensitized solar cell photoelectronic device along with N719 dyes and the optimal power conversion efficiency was 28% higher than that of single-dye sensitization. These results show that MoV 60 polyoxometalate could serve as an ideal model for the design and synthesis of all-inorganic molecular light-absorbers for other light-driven processes in the future.

Enhanced Overall Water Splitting by a Zirconium-Doped TaON-Based Photocatalyst

Solar-powered one-step-excitation overall water splitting (OWS) using semiconducting materials is a simple means of achieving scalable and sustainable hydrogen production. While tantalum oxynitride (TaON) is one of the few photocatalysts capable of promoting OWS via single-step visible-light excitation, the efficiency of this process remains extremely poor. The present work employed 15 nm amorphous Ta₂ O₅ ⋅3.3 H₂ O nanoparticles as a new precursor together with Zr doping and an optimized nitridation duration to synthesize a TaON-based photocatalyst with reduced particle sizes and low defect densities. Upon loading with Ru/Cr₂ O₃ /IrO₂ cocatalysts, this material exhibited stoichiometric water splitting into hydrogen and oxygen, with an order of magnitude improvement in efficiency. Our findings demonstrate the importance of inventing/selecting the appropriate synthetic precursor and of defect control for fabricating active OWS photocatalysts.

Photo-Charging of Li(Ni0.65Co0.15Mn0.20)O2 Lithium-Ion Battery Using Silicon Solar Cells

This study reports an integrated device in which a lithium-ion battery (LIB) and Si solar cells are interconnected. The LIB is fabricated using the Li(Ni_0.65Co_0.15Mn_0.20)O₂ (NCM622) cathode and the Li₄Ti₅O₁₂ (LTO) anode. The surface and shape morphologies of the NCM and LTO powders were investigated by field emission scanning electron microscopy (FE-SEM). In addition, the structural properties were thoroughly examined by X-ray diffraction (XRD). Further, their electrochemical characterization was carried out on a potentiostat. The specific discharge capacity of the NCM cathode (half-cell) was 188.09 mAh/g at 0.1 C current density. In further experiments, the NCM-LTO full-cell has also shown an excellent specific capacity of 160 mAh/g at a high current density of 1 C. Additionally, the capacity retention was outstanding, with 99.63% at 1 C after 50 cycles. Moreover, to meet the charging voltage requirements of the NCM-LTO full-cell, six Si solar cells were connected in series. The open-circuit voltage (V_OC) and the short-circuit photocurrent density (J_SC) for the Si solar cells were 3.37 V and 5.42 mA/cm². The calculated fill factor (FF) and efficiency for the Si solar cells were 0.796 and 14.54%, respectively. Lastly, the integrated device has delivered a very high-power conversion-storage efficiency of 7.95%.

Novel solution synthesis of the overlooked cubic phase Cu2GeTe3 nanocrystals for optoelectronic devices

Herein, for the first time, we present a novel solution method for controllable synthesis of the overlooked cubic phase Cu₂GeTe₃ nanocrystals. The resulting Cu₂GeTe₃ nanocrystals are of high quality with monodispersed size and uniform shape. Optical characterization demonstrates that Cu₂GeTe₃ nanocrystals have a broad absorption in the visible to near-infrared region. Furthermore, an optoelectronic device based on Cu₂GeTe₃ nanocrystals exhibits excellent stability, reproducibility and responsivity. The novel synthetic route presented here not only can open a new avenue for fabricating Cu₂GeTe₃ nanocrystals, especially at the nanoscale, but also may further expand their applications.

Recent advances and perspectives for solar-driven water splitting using particulate photocatalysts

The conversion and storage of solar energy to chemical energy via artificial photosynthesis holds significant potential for optimizing the energy situation and mitigating the global warming effect. Photocatalytic water splitting utilizing particulate semiconductors offers great potential for the production of renewable hydrogen, while this cross-road among biology, chemistry, and physics features a topic with fascinating interdisciplinary challenges. Progress in photocatalytic water splitting has been achieved in recent years, ranging from fundamental scientific research to pioneering scalable practical applications. In this review, we focus mainly on the recent advancements in terms of the development of new light-absorption materials, insights and strategies for photogenerated charge separation, and studies towards surface catalytic reactions and mechanisms. In particular, we emphasize several efficient charge separation strategies such as surface-phase junction, spatial charge separation between facets, and polarity-induced charge separation, and also discuss their unique properties including ferroelectric and photo-Dember effects on spatial charge separation. By integrating time- and space-resolved characterization techniques, critical issues in photocatalytic water splitting including photoinduced charge generation, separation and transfer, and catalytic reactions are analyzed and reviewed. In addition, photocatalysts with state-of-art efficiencies in the laboratory stage and pioneering scalable solar water splitting systems for hydrogen production using particulate photocatalysts are presented. Finally, some perspectives and outlooks on the future development of photocatalytic water splitting using particulate photocatalysts are proposed.

In Situ Simultaneous Cavitation-Doping Approach for Constructing Bimetallic Metal-Organic Framework Hollow Nanospheres with Enhanced Electrocatalytic Hydrogen Production

This Communication demonstrates a novel and in situ simultaneous cavitation-doping (SCD) approach to construct bimetallic metal-doped cobalt metal-organic framework hollow nanospheres (CoM-MOF HNSs, with M = Ru or Fe). The key point of the SCD approach is the careful balance between the kinetics of Co-MOF being etched and the coordinative growth of a more stable CoM-MOF shell induced by Lewis acid (MCl₃, with M = Ru or Fe). Our work provides a new method to synthesize bimetallic hollow MOFs and benefits the development of electrocatalysts.

Modifying Ti-Based Gas Diffusion Layer Passivation for Polymer Electrolyte Membrane Water Electrolysis via Electrochemical Nitridation

A gas diffusion layer represents an important element of collector and stack components used in polymer electrolyte membrane (PEM) water electrolyzers (WE). Nowadays, titanium-based gas diffusion layers (GDLs) have high stability and are frequently employed as anode GDLs, yet reliability issues emerging from passivation have limited their practical deployment. Hence, we develop an inexpensive way of producing high conductivity and corrosion resistance of Ti-based GDLs through electrochemical nitridation. The morphology and content of the nitride phase on the surface of the Ti felt GDL are efficiently regulated by adjusting reduction potential and reaction time. According to X-ray photoelectron spectroscopy studies, the modified Ti felt is coated with ammonium ions and nitrogen-incorporated oxides, namely, TiN/TiO_x, on the surface. The nitride surface shows a low interfacial contact resistance (ca. 1.0 mΩ cm² at 140 N/cm²) and excellent corrosion resistance (0.920 μA cm^-2) in the simulated PEM WE environments. The electrochemical nitridation provides an economic way to introducing N layers on the surface of the Ti-based GDL with high performance, which is very promising for efficient PEM water electrolysis.

A lotus-inspired 3D biomimetic design toward an advanced solar steam evaporator with ultrahigh efficiency and remarkable stability

Developing advanced solar-driven interfacial evaporators with both ultrahigh energy efficiency and long-term tolerability is highly desired but still a great challenge. Herein, inspired by the natural lotus, we develop a high-performance solar interfacial evaporator with a novel 3D biomimetic architecture. The lotus-inspired biomimetic evaporator (LBE) combines three key components, including a large "leaf" having strong solar energy absorption ability, hydrophilic "stems" working as water transport channels, and lotus root-like porous "roots" with minimized heat loss for improved respiration. The photothermal part in the LBE, analogous to a lotus leaf, possesses Janus wettability with a hydrophobic side above and a hydrophilic side below, which is achieved by a scalable method of in situ inducing ZIF-67 nanocubes into an electrospun fiber film followed by pyrolysis. In particular, the top side has a unique hierarchical network structure consisting of long porous carbon nanofibers with internally dispersed metal oxide nanocrystals, leading to highly efficient solar absorption of 91.37%. The 3D-LBE exhibits an extremely high evaporation rate of 3.23 kg m^-2 h^-1 and energy efficiency reaching 153.20% under 1-sun, which exceeds the theoretical limit and is the highest recorded, to the best of our knowledge. Notably, the 3D-LBE also shows impressive pollutant removal capabilities assuring long-term interfacial evaporation stability. The high-performance LBE promises many applications, such as wastewater treatment, sea salt production, and metal recovery.

New black indium oxide—tandem photothermal CO2-H2 methanol selective catalyst

It has long been known that the thermal catalyst Cu/ZnO/Al₂O₃(CZA) can enable remarkable catalytic performance towards CO₂ hydrogenation for the reverse water-gas shift (RWGS) and methanol synthesis reactions. However, owing to the direct competition between these reactions, high pressure and high hydrogen concentration (≥75%) are required to shift the thermodynamic equilibrium towards methanol synthesis. Herein, a new black indium oxide with photothermal catalytic activity is successfully prepared, and it facilitates a tandem synthesis of methanol at a low hydrogen concentration (50%) and ambient pressure by directly using by-product CO as feedstock. The methanol selectivities achieve 33.24% and 49.23% at low and high hydrogen concentrations, respectively.

Harsh reaction conditions are generally required for CO2 hydrogenation to shift the thermodynamic equilibrium towards methanol synthesis. Here, a new black indium oxide with two types of active sites, frustrated Lewis pairs and oxygen vacancies, is prepared, and facilitates a tandem synthesis of methanol at a low hydrogen concentration (50%) and ambient pressure.

Inter-facet junction effects on particulate photoelectrodes

Particulate semiconductor photocatalysts are paramount for many solar energy conversion technologies. In anisotropically shaped photocatalyst particles, the different constituent facets may form inter-facet junctions at their adjoining edges, analogous to lateral two-dimensional (2D) heterojunctions or pseudo-2D junctions made of few-layer 2D materials. Using subfacet-level multimodal functional imaging, we uncover inter-facet junction effects on anisotropically shaped bismuth vanadate (BiVO₄) particles and identify the characteristics of near-edge transition zones on the particle surface, which underpin the whole-particle photoelectrochemistry. We further show that chemical doping modulates the widths of such near-edge surface transition zones, consequently altering particles' performance. Decoupled facet-size scaling laws further translate inter-facet junction effects into quantitative particle-size engineering principles, revealing surprising multiphasic size dependences of whole-particle photoelectrode performance. The imaging tools, the analytical framework and the inter-facet junction concept pave new avenues towards understanding, predicting and engineering (opto)electronic and photoelectrochemical properties of faceted semiconducting materials, with broad implications in energy science and semiconductor technology.

Self-supported Co9S8-Ni3S2-CNTs/NF electrode with superwetting multistage micro-nano structure for efficient bifunctional overall water splitting

Electrochemical water splitting for hydrogen production using cost-effective and high-efficiency electrocatalysts in alkaline electrolytes is of great significance for solving energy crisis and environmental pollution. Herein, we reported a superhydrophilic and underwater superaerophobic multistage layered micro-nano structure ofCo₉S₈-Ni₃S₂-CNTs/NF on nickel foam (NF) prepared by a simple one-step hydrothermal procedure. Particularly, the multistage layered micro-nano structure makes the electrode superhydrophilic and superaerophobic, which can facilitate the exposure of active sites, accelerate the tansfer of electrolyte and the release of gas bubbles. Consequently, the rough electrode demonstrated excellent catalytic performance in alkaline condition, which only need a low overpotential 127 mV for oxygen evolution reaction (OER) and 243 mV for hydrogen evolution reaction (HER) at 10 mA cm^-2 and can keep a long durability for 10 h at 10 mA cm^-2. In addition, the production of hydrogen in an electrolytic water device with Co₉S₈-Ni₃S₂-CNTs/NF as bifunctional electrode prowered by the electricity derived from solar and wind energy in laboratory condition was artificially simulated. This work represents a perspective in improving the electrocatalytic performance of water splitting by structure and wettability regulation and opens a new avenue for clean energy generation.

Fibrous Aerogels for Solar Vapor Generation

Solar-driven vapor generation is emerging as an eco-friendly and cost-effective water treatment technology for harvesting solar energy. Aerogels are solid materials with desirable high-performance properties, including low density, low thermal conductivity, and high porosity with a large internal surface, which exhibit outstanding performance in the area of solar vapor generation. Using fibers as building blocks in aerogels could achieve unexpected performance in solar vapor generation due to their entangled fibrous network and high surface area. In this review, based on the fusion of the one-dimensional fibers and three-dimensional porous aerogels, we discuss recent development in fibrous aerogels for solar vapor generation based on building blocks synthesis, photothermal materials selection, pore structures construction and device design. Thermal management and water management of fibrous aerogels are also evaluated to improve evaporation performance. Focusing on materials science and engineering, we overview the key challenges and future research opportunities of fibrous aerogels in both fundamental research and practical application of solar vapor generation technology.

Photoelectrochemical energy storage materials: design principles and functional devices towards direct solar to electrochemical energy storage

Advanced solar energy utilization technologies have been booming for carbon-neutral and renewable society development. Photovoltaic cells now hold the highest potential for widespread sustainable electricity production and photo(electro)catalytic cells could supply various chemicals. However, both of them require the connection of energy storage devices or matter to compensate for intermittent sunlight, suffering from complicated structures and external energy loss. Newly developed photoelectrochemical energy storage (PES) devices can effectively convert and store solar energy in one two-electrode battery, simplifying the configuration and decreasing the external energy loss. Based on PES materials, the PES devices could realize direct solar-to-electrochemical energy storage, which is fundamentally different from photo(electro)catalytic cells (solar-to-chemical energy conversion) and photovoltaic cells (solar-to-electricity energy conversion). This review summarizes a critically selected overview of advanced PES materials, the key to direct solar to electrochemical energy storage technology, with the focus on the research progress in PES processes and design principles. Based on the specific discussions of the performance metrics, the bottlenecks of PES devices, including low efficiency and deteriorative stability, are also discussed. Finally, several perspectives of potential strategies to overcome the bottlenecks and realize practical photoelectrochemical energy storage devices are presented.

Interfacial interaction induced OER activity of MOF derived superhydrophilic Co3O4-NiO hybrid nanostructures

Electrocatalytic water splitting is one of the key technologies for future energy systems envisioned for the storage of energy obtained from variable renewables and green fuels. The development of efficient, durable, Earth-abundant and cheap electrocatalysts for the oxygen evolution reaction is a scorching area of research. The oxygen evolution reaction has huge potential for fuel cell and metal-air battery applications. Herein, we reported interfacially interacted and uniformly decorated Co₃O₄-NiO hybrid nanostructures formed by a metal-organic framework (Co₂-BDC(OH)₂) using BDC as a linker to the metal center. The fine nanosheets of Co₂-BDC(OH)₂ were first uniformly grown over the honeycomb-like structure of nickel foam (NF). After controlled calcination of these nanosheets/NF composites, a uniformly decorated, binder-free Co₃O₄-NiO/NF electrocatalyst was synthesized. The transformation of Co₂-BDC(OH)₂/NF into Co₃O₄-NiO/NF was characterized by several techniques such as powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy, transmission electron microscopy, etc. The catalyst exhibits a low overpotential of 311 mV vs. RHE at 10 mA cm^-2 current density. The catalyst also shows long-term stability (24 h) with a Tafel slope value of 90 mV dec^-1. The obtained experimental results are also in-line with the theoretical data acquired from model systems.

Highly Efficient Photothermal Conversion and Water Transport during Solar Evaporation Enabled by Amorphous Hollow Multishelled Nanocomposites

Solar evaporation, which enables water purification without consuming fossil fuels, has been considered the most promising strategy to address global scarcity of drinkable water. However, the suboptimal structure and composition designs still result in a trade-off between photothermal conversion, water transport, and tolerance to harsh environments. Here, an ultrastable amorphous Ta₂ O₅ /C nanocomposite is designed with a hollow multishelled structure (HoMS) for solar evaporation. This HoMS results in highly efficient photoabsorption and photothermal conversion, as well as a decrease of the actual water evaporation enthalpy. A superfast evaporation speed of 4.02 kg m^-2 h^-1 is achieved. More importantly, a World Health Organization standard drinkable water can be achieved from seawater, heavy-metal- and bacteria-containing water, and even from extremely acidic/alkaline or radioactive water sources. Notably, the concentration of pseudovirus SC2-P can be decreased by 6 orders of magnitude after evaporation.

Heterogenization of Molecular Water Oxidation Catalysts in Electrodes for (Photo)Electrochemical Water Oxidation

Water oxidation is still one of the most important challenges to develop efficient artificial photosynthetic devices. In recent decades, the development and study of molecular complexes for water oxidation have allowed insight into the principles governing catalytic activity and the mechanism as well as establish ligand design guidelines to improve performance. However, their durability and long-term stability compromise the performance of molecular-based artificial photosynthetic devices. In this context, heterogenization of molecular water oxidation catalysts on electrode surfaces has emerged as a promising approach for efficient long-lasting water oxidation for artificial photosynthetic devices. This review covers the state of the art of strategies for the heterogenization of molecular water oxidation catalysts onto electrodes for (photo)electrochemical water oxidation. An overview and description of the main binding strategies are provided explaining the advantages of each strategy and their scope. Moreover, selected examples are discussed together with the the differences in activity and stability between the homogeneous and the heterogenized system when reported. Finally, the common design principles for efficient (photo)electrocatalytic performance summarized.

Computational Scaling Relationships Predict Experimental Activity and Rate-Limiting Behavior in Homogeneous Water Oxidation

While computational screening with first-principles density functional theory (DFT) is essential for evaluating candidate catalysts, limitations in accuracy typically prevent the prediction of experimentally relevant activities. Exemplary of these challenges are homogeneous water oxidation catalysts (WOCs) where differences in experimental conditions or small changes in ligand structure can alter rate constants by over an order of magnitude. Here, we compute mechanistically relevant electronic and energetic properties for 19 mononuclear Ru transition-metal complexes (TMCs) from three experimental water oxidation catalysis studies. We discover that 15 of these TMCs have experimental activities that correlate with a single property, the ionization potential of the Ru(II)-O₂ catalytic intermediate. This scaling parameter allows the quantitative understanding of activity trends and provides insight into the rate-limiting behavior. We use this approach to rationalize differences in activity with different experimental conditions, and we qualitatively analyze the source of distinct behavior for different electronic states in the other four catalysts. Comparison to closely related single-atom catalysts and modified WOCs enables rationalization of the source of rate enhancement in these WOCs.

Laser-treated wood for high-efficiency solar thermal steam generation

Solar-driven water vaporization is considered one of the most sustainable ways to solve water scarcity. The design of highly efficient solar absorber systems has received extensive attention. Here, we report a novel light absorption material for water evaporation using laser-treated wood. The obtained laser-treated wood possesses interconnected 3D porous networks formed by the random construction of carbon arrays and a hydrophilic surface due to the oxygen implantation by laser treatment. When under 1 sun solar-simulated light irradiation (1 kW m⁻²), the surface temperatures of dry and water-saturated wood reach 59.5 °C and 40.4 °C, respectively, indicating good heat localization. As a result, the laser-treated wood under 1 sun illumination shows high solar to vapor efficiencies of 93.1% and 92.6% for pure water and seawater, respectively, which are higher than that of most wood-based reported photo-thermal conversion materials. Therefore, the fabricated laser-treated wood may pave the way for harvesting solar energy to produce clean water at low cost.

Solar-driven water vaporization is considered one of the most sustainable ways to solve waterscarcity.

Coupling of the water-splitting mechanism and doping-mixture method to design a novel Cr-perovskite for rapid and efficient solar thermochemical H2 production

The water-splitting mechanism-supported material design of a novel Cr-perovskite by Zr doping and ceria mixing for promising H2 production.

Solution-phase controlled synthesis of Cu3NbSe4 nanocrystals for optoelectronic applications

Cu3NbSe4 nanocrystals with a cubic phase, monodisperse size and uniform shape synthesized by a facile colloidal method exhibit excellent optoelectronic properties.

Observation of 4th-order water oxidation kinetics by time-resolved photovoltage spectroscopy

Artificial photo-driven water oxidation has been proposed over half a century through a four-charge involved multiple-step oxygen evolution process. However, the knowledge of the intrinsic activity, such as the rate-law of the water oxidation reactions, has been inadequately studied. Up to date, the highest order reported is the third one under photoelectrochemical condition. In this work, we identified the fourth-order charge decay reactions on hematite by using a time-resolved surface photovoltage probe technique. A theoretical turnover frequency (TOF) > 100 nm^-2·s^-1 can be expected for O₂ molecules when the hole density >0.1 nm^-2. This work demonstrates a facile and robust method to investigate the high-order reaction kinetics. More excitingly, this research built the bridge between the rate-law, rate-determining step, and energy barrier of intermediates.

Insights into the light-driven hydrogen evolution reaction of mesoporous graphitic carbon nitride decorated with Pt or Ru nanoparticles

Ru or Pt nanoparticles have been prepared following the organometallic approach and deposited onto the surface of mesoporous graphitic carbon nitride (mpg-CN). Three different Ru-based samples have also been compared to investigate the effect of 4-phenylpyridine as a stabilizing agent. The photocatalytic performance towards the hydrogen evolution reaction (HER) has been tested showing that all hybrid systems clearly outperform the photocatalytic activity of bare mpg-CN. In particular, Pt-decorated mpg-CN yields the largest H₂ production upon visible-light irradiation (870 μmol h^-1 g^-1, TOF = 14.1 h^-1, TON = 339 after 24 h) when compared with the Ru-based samples (137-155 μmol h^-1 g^-1, TOFs between 2.3-2.7 h^-1, TONs between 54-57 after 24 h). Long-term photochemical tests (up to 65 h irradiation) show also an improved stability of the Pt-based samples over the Ru counterpart. Photophysical experiments aimed at rationalizing the photocatalytic performance of the different hybrid systems elucidate that the enhanced activity of the Pt-decorated mpg-CN over the Ru-based analogues arises from improved electron transfer kinetics from mpg-CN to the metal nanoparticles.

Role of Pt and PtO2 in the Oxygen-Evolution Reaction in the Presence of Iron under Alkaline Conditions

The oxygen-evolution reaction (OER) through water oxidation is an inevitable reaction for water splitting toward storing energy. However, OER is a four-electron and slow reaction, which is also a bottleneck for water splitting. To find the role of Pt and PtO₂ on the OER in the presence of Fe, the electrochemistry of Pt foil and PtO₂ is investigated in the absence/presence of K₂FeO₄ as a soluble Fe salt at pH ≈ 13. After the addition of K₂FeO₄, a remarkable increase in the OER is recorded in the presence of Pt or PtO₂. The obtained catalysts were characterized by operando visible spectroscopy, high-resolution transmission electron microscopy, scanning electron microscopy, electron-spin resonance spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and electrochemical methods. KOH solutions usually contain Fe and/or Ni impurities. It is found that neither Pt nor PtO₂ is an OER catalyst in a Ni/Fe-free KOH, and even at an overpotential of 570 mV in purified KOH (pH ≈ 13), no clear OER was observed.

Nanostructured Photothermal Materials for Environmental and Catalytic Applications

Solar energy is a green and sustainable clean energy source. Its rational use can alleviate the energy crisis and environmental pollution. Directly converting solar energy into heat energy is the most efficient method among all solar conversion strategies. Recently, various environmental and energy applications based on nanostructured photothermal materials stimulated the re-examination of the interfacial solar energy conversion process. The design of photothermal nanomaterials is demonstrated to be critical to promote the solar-to-heat energy conversion and the following physical and chemical processes. This review introduces the latest photothermal nanomaterials and their nanostructure modulation strategies for environmental (seawater evaporation) and catalytic (C1 conversion) applications. We present the research progress of photothermal seawater evaporation based on two-dimensional and three-dimensional porous materials. Then, we describe the progress of photothermal catalysis based on layered double hydroxide derived nanostructures, hydroxylated indium oxide nanostructures, and metal plasmonic nanostructures. Finally, we present our insights concerning the future development of this field.

Versatile Redox-Active Organic Materials for Rechargeable Energy Storage

With the ever-increasing demand on energy storage systems and subsequent mass production, there is an urgent need for the development of batteries with not only improved electrochemical performance but also better sustainability-related features such as environmental friendliness and low production cost. To date, transition metals that are sparse have been centrally employed in energy storage devices ranging from portable lithium ion batteries (e.g., cobalt and nickel) to large-scale redox flow batteries (e.g., vanadium). Toward the sustainable battery chemistry, there are ongoing efforts to replace the transition metal-based electrode materials in these systems to redox-active organic materials (ROMs). Most ROMs are composed of the earth abundant elements (e.g., carbon, nitrogen, oxygen, sulfur), thus are less restrained by the resource, and their production does not require high-energy consuming processes. Furthermore, the structural diversity and chemical tunability of organic compounds make them more attractive for the versatile design of future energy storage systems. Accordingly, the timely development of high-performance ROM-based electrodes would expedite the shift from the current resource-limited battery chemistry to more sustainable energy solutions.In this Account, we provide an overview of the endeavors to employ and develop ROMs as high-performance active materials for various battery systems. Diverse approaches will be introduced starting from the new ROM design mimicking the energy carrying molecules in biological metabolism to the chemical modifications to tailor the properties for specific battery systems. The molecular redesign of ROM, for example, can be carried out by substituting heteroatoms in the redox center, which leads to the enhancement of the redox potential by the inductive effect. Or, tailoring the ROM molecule by removing redox-inactive functionals results in a reduced molecular weight, thereby an increased specific capacity. The intrinsic limitations of ROMs, such as the low electrical conductivity and the dissolving nature, have been under extensive scrutiny; however, they can be partly addressed through efforts including intermolecular fusion and/or nanoscale hybridization with a conducting scaffold. On the other hand, this problematic dissolving nature of ROMs makes them appealing for some new battery configurations such as redox flow batteries that employ the liquid-state active materials. The high solubility and the stability of the ROM were found to be beneficial in attaining the enhanced energy density and the cycle stability of flow batteries, which could be further optimized by the chemical modifications of ROMs. Besides the role of active materials, the redox activity of ROMs has also enabled their use as catalysts to promote the electrode reaction in metal-air batteries. The redox capability of the ROM was often proven to be effective in the solution-based redox mediation that facilitates both the charging and discharging reaction in metal-air batteries. Finally, we conclude this account by proposing the future research directions regarding the fundamental electrochemistry and the further practical development of ROMs for the sustainable rechargeable energy storage.

Nanoscale electrodeposition: Dimension control and 3D conformality

Electrodeposition with a long history has been considered one of the important synthesis techniques for applying various applications. It is a feasible route for fabricating nanostructures using diverse materials due to its simplicity, cost-effectiveness, flexibility, and ease of reaction control. Herein, we mainly focus on the nanoscale electrodeposition with respect to dimension control and three-dimensional (3D) conformality. The principles of electrodeposition, dimensional design of materials, and uniform coatings on various substrates are presented. We introduce that manipulating synthesis parameters such as precursors, applied current/voltage, and additives affect the synthesis reaction, resulting in not only dimensional control of materials from three-dimensional structures to zero-dimensional atomic-level but also conformal coatings on complicated substrates. Various cases regarding morphology control of metal (hydro)oxides, metals, and metal-organic frameworks according to electrodeposition conditions are summarized. Lastly, recent studies of applications such as batteries, photoelectrodes, and electrocatalysts using electrodeposited materials are summarized. This review represents significant advances in the nanoscale design of materials through methodological approaches, which are highly attractive from both academic and commercial aspects.

Structural and Componential Engineering of Co2P&CoP@N-C Nanoarrays for Energy-Efficient Hydrogen Production from Water Electrolysis

The development of electrocatalysts for efficient water splitting is a pivotal and challenging task. Transition-metal phosphides (TMPs) have been known as one of the most promising candidates for the efficient hydrogen evolution reaction (HER) due to their favorable intrinsic reactivity. However, structural engineering related to the gas bubbles evolution and tiny regulation of components concerned with the electronic structure remained as a significant challenge that requires further optimization. Herein, the nanoarrays (NAs) composed of ultrasmall Co₂P and CoP nanoparticle-embedded N-doped carbon matrix (Co₂P&CoP@N-C) are prepared and demonstrated an overpotential of 62.8 ± 4.7 mV at 10 mA cm^-2 in 1.0 M KOH. The nanoarray-structured electrocatalyst revealed the superaerophobicity and facilitates the detachment of the in situ formed hydrogen gas bubbles, ensuring abundant catalytic sites and electrode-electrolyte interface for the mass transfer process. The amount of P doping modulated the local electron density around Co and P atoms, which attains a favorable compromise to afford sufficient electrons for the electrocatalysis and inhibit the negative influence of H₂ desorption. Significantly, the lowered overpotential induced by the electrocatalyst surface architecture is much stronger than that of the component content and promotes the electrocatalytic activity.

Bioinspired Trinuclear Copper Catalyst for Water Oxidation with a Turnover Frequency up to 20000 s-1

Solar-powered water splitting is a dream reaction for constructing an artificial photosynthetic system for producing solar fuels. Natural photosystem II is a prototype template for research on artificial solar energy conversion by oxidizing water into molecular oxygen and supplying four electrons for fuel production. Although a range of synthetic molecular water oxidation catalysts have been developed, the understanding of O-O bond formation in this multielectron and multiproton catalytic process is limited, and thus water oxidation is still a big challenge. Herein, we report a trinuclear copper cluster that displays outstanding reactivity toward catalytic water oxidation inspired by multicopper oxidases (MCOs), which provides efficient catalytic four-electron reduction of O₂ to water. This synthetic mimic exhibits a turnover frequency of 20000 s^-1 in sodium bicarbonate solution, which is about 150 and 15 times higher than that of the mononuclear Cu catalyst (F-N₂O₂Cu, 131.6 s^-1) and binuclear Cu₂ complex (HappCu₂, 1375 s^-1), respectively. This work shows that the cooperation between multiple metals is an effective strategy to regulate the formation of O-O bond in water oxidation catalysis.

Dynamics of photoconversion processes: the energetic cost of lifetime gain in photosynthetic and photovoltaic systems

The continued development of solar energy conversion technologies relies on an improved understanding of their limitations. In this review, we focus on a comparison of the charge carrier dynamics underlying the function of photovoltaic devices with those of both natural and artificial photosynthetic systems. The solar energy conversion efficiency is determined by the product of the rate of generation of high energy species (charges for solar cells, chemical fuels for photosynthesis) and the energy contained in these species. It is known that the underlying kinetics of the photophysical and charge transfer processes affect the production yield of high energy species. Comparatively little attention has been paid to how these kinetics are linked to the energy contained in the high energy species or the energy lost in driving the forward reactions. Here we review the operational parameters of both photovoltaic and photosynthetic systems to highlight the energy cost of extending the lifetime of charge carriers to levels that enable function. We show a strong correlation between the energy lost within the device and the necessary lifetime gain, even when considering natural photosynthesis alongside artificial systems. From consideration of experimental data across all these systems, the emprical energetic cost of each 10-fold increase in lifetime is 87 meV. This energetic cost of lifetime gain is approx. 50% greater than the 59 meV predicted from a simple kinetic model. Broadly speaking, photovoltaic devices show smaller energy losses compared to photosynthetic devices due to the smaller lifetime gains needed. This is because of faster charge extraction processes in photovoltaic devices compared to the complex multi-electron, multi-proton redox reactions that produce fuels in photosynthetic devices. The result is that in photosynthetic systems, larger energetic costs are paid to overcome unfavorable kinetic competition between the excited state lifetime and the rate of interfacial reactions. We apply this framework to leading examples of photovoltaic and photosynthetic devices to identify kinetic sources of energy loss and identify possible strategies to reduce this energy loss. The kinetic and energetic analyses undertaken are applicable to both photovoltaic and photosynthetic systems allowing for a holistic comparison of both types of solar energy conversion approaches.