Layered High-Entropy Metallic Glasses for Photothermal CO2 Methanation.

High entropy alloys and metallic glasses, as two typical metastable nanomaterials, have attracted tremendous interest in energy conversion catalysis due to their high reactivity in nonequilibrium states. Herein, a novel nanomaterial, layered high entropy metallic glass (HEMG), in a higher energy state than low-entropy alloys and its crystalline counterpart due to both the disordered elemental and structural arrangements, is synthesized. Specifically, the MnNiZrRuCe HEMG exhibits highly enhanced photothermal catalytic activity and long-term stability. An unprecedented CO2 methanation rate of 489 mmol g-1 h-1 at 330 °C is achieved, which is, to the authors' knowledge, the highest photothermal CO2 methanation rate in flow reactors. The remarkable activity originates from the abundant free volume and high internal energy state of HEMG, which lead to the extraordinary heterolytic H2 dissociation capacity. The high-entropy effect also ensures the excellent stability of HEMG for up to 450 h. This work not only provides a new perspective on the catalytic mechanism of HEMG, but also sheds light on the great catalytic potential in future carbon-negative industry.

Unraveling the Transformation from Type-II to Z-Scheme in Perovskite-Based Heterostructures for Enhanced Photocatalytic CO2 Reduction.

The ability to create perovskite-based heterostructures with desirable charge transfer characteristics represents an important endeavor to render a set of perovskite materials and devices with tunable optoelectronic properties. However, due to similar material selection and band alignment in type-II and Z-scheme heterostructures, it remains challenging to obtain perovskite-based heterostructures with a favorable electron transfer pathway for photocatalysis. Herein, we report a robust tailoring of effective charge transfer pathway in perovskite-based heterostructures via a type-II to Z-scheme transformation for highly efficient and selective photocatalytic CO2 reduction. Specifically, CsPbBr3/TiO2 and CsPbBr3/Au/TiO2 heterostructures are synthesized and then investigated by ultrafast spectroscopy. Moreover, taking CsPbBr3/TiO2 and CsPbBr3/Au/TiO2 as examples, operando experiments and theoretical calculations confirm that the type-II heterostructure could be readily transformed into a Z-scheme heterostructure through establishing a low-resistance Ohmic contact, which indicates that a fast electron transfer pathway is crucial in Z-scheme construction, as further demonstrated by CsPbBr3/Ag/TiO2 and CsPbBr3/MoS2 heterostructures. In contrast to pristine CsPbBr3 and CsPbBr3/TiO2, the CsPbBr3/Au/TiO2 heterostructure exhibits 5.4- and 3.0-fold enhancement of electron consumption rate in photocatalytic CO2 reduction. DFT calculations and in situ diffuse reflectance infrared Fourier transform spectroscopy unveil that the superior CO selectivity is attributed to the lower energy of *CO desorption than that of hydrogenation to *HCO. This meticulous design sheds light on the modification of perovskite-based multifunctional materials and enlightens conscious optimization of semiconductor-based heterostructures with desirable charge transfer for catalysis and optoelectronic applications.

Potential window alignment regulating ion transfer in faradaic junctions for efficient photoelectrocatalysis.

In the past decades, a band alignment theory has become a basis for designing different high-performance semiconductor devices, such as photocatalysis, photoelectrocatalysis, photoelectrostorage and third-generation photovoltaics. Recently, a faradaic junction model (coupled electron and ion transfer) has been proposed to explain charge transfer phenomena in these semiconductor heterojunctions. However, the classic band alignment theory cannot explain coupled electron and ion transfer processes because it only regulates electron transfer. Therefore, it is very significant to explore a suitable design concept for regulating coupled electron and ion transfer in order to improve the performance of semiconductor heterojunctions. Herein, we propose a potential window alignment theory for regulating ion transfer and remarkably improving the photoelectrocatalytic performance of a MoS2/Cd-Cu2ZnSnS4 heterojunction photocathode. Moreover, we find that a faradaic potential window, rather than the band position of the intermediate layer, is a criterion for identifying interface charge transfer direction. This finding can offer different perspectives for designing high-performance semiconductor heterojunctions with suitable potential windows for solar energy conversion and storage.

Wettability Engineering of Solar Methanol Synthesis.

Engineering the wettability of surfaces with hydrophobic organics has myriad applications in heterogeneous catalysis and the large-scale chemical industry; however, the mechanisms behind may surpass the proverbial hydrophobic kinetic benefits. Herein, the well-studied In2O3 methanol synthesis photocatalyst has been used as an archetype platform for a hydrophobic treatment to enhance its performance. With this strategy, the modified samples facilitated the tuning of a wide range of methanol production rates and selectivity, which were optimized at 1436 µmol gcat-1 h-1 and 61%, respectively. Based on in situ DRIFTS and temperature-programmed desorption-mass spectrometry, the surface-decorated alkylsilane coating on In2O3 not only kinetically enhanced the methanol synthesis by repelling the produced polar molecules but also donated surface active H to facilitate the subsequent hydrogenation reaction. Such a wettability design strategy seems to have universal applicability, judged by its success with other CO2 hydrogenation catalysts, including Fe2O3, CeO2, ZrO2, and Co3O4. Based on the discovered kinetic and mechanistic benefits, the enhanced hydrogenation ability enabled by hydrophobic alkyl groups unleashes the potential of the surface organic chemistry modification strategy for other important catalytic hydrogenation reactions.

Room-Temperature Laser Planting of High-Loading Single-Atom Catalysts for High-Efficiency Electrocatalytic Hydrogen Evolution.

Despite stunning progress in single-atom catalysis (SAC), it remains a grand challenge to yield a high loading of single atoms (SAs) anchored on substrates. Herein, we report a one-step laser-planting strategy to craft SAs of interest under an atmospheric temperature and pressure on various substrates including carbon, metals, and oxides. Laser pulses render concurrent creation of defects on the substrate and decomposition of precursors into monolithic metal SAs, which are immobilized on the as-produced defects via electronic interactions. Laser planting enables a high defect density, leading to a record-high loading of SAs of 41.8 wt %. Our strategy can also synthesize high-entropy SAs (HESAs) with the coexistence of multiple metal SAs, regardless of their distinct characteristics. An integrated experimental and theoretical study reveals that superior catalytic activity can be achieved when the distribution of metal atom content in HESAs resembles the distribution of their catalytic performance in a volcano plot of electrocatalysis. The noble-metal mass activity for a hydrogen evolution reaction within HESAs is 11-fold over that of commercial Pt/C. The laser-planting strategy is robust, opening up a simple and general route to attaining an array of low-cost, high-density SAs on diverse substrates under ambient conditions for electrochemical energy conversion.

Bipolarized intrinsic faradaic layer on a semiconductor surface under illumination.

Interface charge transfer plays a key role in the performance of semiconductors for different kinds of solar energy utilization, such as photocatalysis, photoelectrocatalysis, photochromism and photo-induced superhydrophilicity. In previous studies, different mechanisms have been used to understand interface charge transfer processes. However, the charge transfer mechanism at the solid/liquid interface remains a controversial topic. Here, taking TiO2 as a model, we find and prove, via experiments, the new characteristic of photo-induced bipolarity of the surface layer (reduction faradaic layer and oxidation faradaic layer) on a semiconductor for the first time. Different from energy level positions in the classic surface states transfer mechanism, the potential window of a surface faradaic layer is located out of the forbidden band. Moreover, we find that the reduction faradaic layer and oxidation faradaic layer serve as electron and hole transfer mediators in photocatalysis, while the bipolarity or mono-polarity of the surface layer on a semiconductor depends on the applied potential in photoelectrocatalysis. The new characteristic of bipolarity can also offer new insights into the charge transfer process at the semiconductor/liquid interface for solar energy utilization.

Strain engineering of high-entropy alloy catalysts for electrocatalytic water splitting.

Developing active and cost-effective bifunctional electrocatalysts for overall water splitting is challenging but mandatory for renewable energy technologies. We report a high-entropy alloy (HEA) of PtIrCuNiCr as a bifunctional electrocatalyst for overall water splitting, which shows a low overpotential of ca. 190 mV at the current density of 10 mA cm-2. Compared with pure metals, HEAs exhibit remarkable surface strain due to severe lattice distortion in their crystal structures. Theoretical calculations reveal that the strain can regulate the binding energy of intermediates on catalysts by adjusting the metal-metal bonding energy. It pushes the HEA toward the top of volcano plots to achieve superior electrocatalytic activity for both hydrogen and oxygen evolution reactions. The strain effect of HEAs on electrocatalysis can be well engineered by tuning the catalyst radius or configurational entropy. This work renders a systematic strain regulation strategy for designing a high-performance HEA catalyst for overall water splitting.

Room-temperature photosynthesis of propane from CO2 with Cu single atoms on vacancy-rich TiO2.

Photochemical conversion of CO2 into high-value C2+ products is difficult to achieve due to the energetic and mechanistic challenges in forming multiple C-C bonds. Herein, an efficient photocatalyst for the conversion of CO2 into C3H8 is prepared by implanting Cu single atoms on Ti0.91O2 atomically-thin single layers. Cu single atoms promote the formation of neighbouring oxygen vacancies (VOs) in Ti0.91O2 matrix. These oxygen vacancies modulate the electronic coupling interaction between Cu atoms and adjacent Ti atoms to form a unique Cu-Ti-VO unit in Ti0.91O2 matrix. A high electron-based selectivity of 64.8% for C3H8 (product-based selectivity of 32.4%), and 86.2% for total C2+ hydrocarbons (product-based selectivity of 50.2%) are achieved. Theoretical calculations suggest that Cu-Ti-VO unit may stabilize the key *CHOCO and *CH2OCOCO intermediates and reduce their energy levels, tuning both C1-C1 and C1-C2 couplings into thermodynamically-favourable exothermal processes. Tandem catalysis mechanism and potential reaction pathway are tentatively proposed for C3H8 formation, involving an overall (20e- - 20H+) reduction and coupling of three CO2 molecules at room temperature.

In situ resource utilization of lunar soil for highly efficient extraterrestrial fuel and oxygen supply.

Building up a lunar settlement is the ultimate aim of lunar exploitation. Yet, limited fuel and oxygen supplies restrict human survival on the Moon. Herein, we demonstrate the in situ resource utilization of lunar soil for extraterrestrial fuel and oxygen production, which may power up our solely natural satellite and supply respiratory gas. Specifically, the lunar soil is loaded with Cu species and employed for electrocatalytic CO2 conversion, demonstrating significant production of methane. In addition, the selected component in lunar soil (i.e. MgSiO3) loaded with Cu can reach a CH4 Faradaic efficiency of 72.05% with a CH4 production rate of 0.8 mL/min at 600 mA/cm2. Simultaneously, an O2 production rate of 2.3 mL/min can be achieved. Furthermore, we demonstrate that our developed process starting from catalyst preparation to electrocatalytic CO2 conversion is so accessible that it can be operated in an unmmaned manner via a robotic system. Such a highly efficient extraterrestrial fuel and oxygen production system is expected to push forward the development of mankind's civilization toward an extraterrestrial settlement.

Encapsulation of Dual-Passivated Perovskite Quantum Dots for Bio-Imaging.

Due to their marvelous electrical and optical properties, perovskite nanocrystals have reached remarkable landmarks in solar cells, light-emitting diodes, and photodetectors. However, the intrinsic instability of ionic perovskites, which would undergo an undesirable phase transition and decompose rapidly in ambient humidity, limits their long-term practical deployment. To address this challenge, halogenated trimethoxysilane as the passivation additive is chosen, which utilizes simultaneous halide and silica passivation to enhance the stability of perovskite nanoparticles via a dual-passivation mechanism. The processable nanoparticles show high photoluminescence quantum yield, tunable fluorescence wavelength, and excellent resistance against air and water, highlighting great potential as green to deep-red bio-labels after further phospholipid encapsulation. This work demonstrates that the dual-passivation mechanism could be used to maintain the long-term stability of ionic crystals, which sheds light on the opportunity of halide perovskite nanoparticles for usage in a humid environment.

Scintillator-based radiocatalytic superoxide radical production for long-term tumor DNA damage.

Photocatalytic materials absorb photons ranging from the ultraviolet to near-infrared region to initiate photocatalytic reactions and have broad application prospects in various fields. However, high-energy ionizing radiations are rarely involved in photocatalytic research. In this study, we proposed a high-energy radiation-based photocatalysis method, namely "radiocatalysis", and prepared a TiO2-coated lanthanide pyrosilicate scintillator (LnPS@TiO2) as the radiocatalytic material. The lanthanide pyrosilicate post-radiation scintillators can efficiently convert radiation energy into ultraviolet energy, which can be resonantly transferred to TiO2 to selectively generate high-yield superoxide radicals (). Compared with traditional radiotherapy, this radiocatalytic process can significantly kill cancer cells while achieving long-term DNA damage by inhibiting the DNA self-repair process. Our research expands the energy response range of photocatalysis and is expected to extend radiocatalysis to the tumor treatment field.

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/CoOx/KBi(aq)/MnOx 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.

High-performance photocatalytic nonoxidative conversion of methane to ethane and hydrogen by heteroatoms-engineered TiO2.

Nonoxidative coupling of methane (NOCM) is a highly important process to simultaneously produce multicarbons and hydrogen. Although oxide-based photocatalysis opens opportunities for NOCM at mild condition, it suffers from unsatisfying selectivity and durability, due to overoxidation of CH4 with lattice oxygen. Here, we propose a heteroatom engineering strategy for highly active, selective and durable photocatalytic NOCM. Demonstrated by commonly used TiO2 photocatalyst, construction of Pd-O4 in surface reduces contribution of O sites to valence band, overcoming the limitations. In contrast to state of the art, 94.3% selectivity is achieved for C2H6 production at 0.91 mmol g-1 h-1 along with stoichiometric H2 production, approaching the level of thermocatalysis at relatively mild condition. As a benchmark, apparent quantum efficiency reaches 3.05% at 350 nm. Further elemental doping can elevate durability over 24 h by stabilizing lattice oxygen. This work provides new insights for high-performance photocatalytic NOCM by atomic engineering.

Photosynthetic microorganisms coupled photodynamic therapy for enhanced antitumor immune effect.

The ideal photodynamic therapy (PDT) should effectively remove the primary tumor, and produce a stronger immune memory effect to inhibit the tumor recurrence and tumor metastasis. However, limited by the hypoxic and immunosuppressive microenvironment, the PDT efficiency is apparently low. Here, Chlorella (Chl.) is exploited to enhance local effect by producing oxygen to reverse hypoxia, and release adjuvants to reverse immunosuppressive microenvironment to enhance abscopal effect afterwards. Results from different animal models indicated that Chl. could enhance local effect and PDT related immune response. Ultimately, Chl. coupled PDT elicited anti-tumor effects toward established primary tumors (inhibition rate: 90%) and abscopal tumors (75%), controlled the challenged tumors (100%) and alleviated metastatic tumors (90%). This Chl. coupled PDT strategy can also produce a stronger anti-tumor immune memory effect. Overall, this Chl. coupled PDT strategy generates enhanced local tumor killing, boosts PDT-induced immune responses and promotes anti-tumor immune memory effect, which may be a great progress for realizing systemic effect of PDT.

Host/Guest Nanostructured Photoanodes Integrated with Targeted Enhancement Strategies for Photoelectrochemical Water Splitting.

Photoelectrochemical (PEC) hydrogen production from water splitting is a green technology that can solve the environmental and energy problems through converting solar energy into renewable hydrogen fuel. The construction of host/guest architecture in semiconductor photoanodes has proven to be an effective strategy to improve solar-to-fuel conversion efficiency dramatically. In host/guest photoanodes, the absorber layer is deposited onto a high-surface-area electron collector, resulting in a significant enhancements in light-harvesting as well as charge collection and separation efficiency. The present review aims to summarize and highlight recent state-of-the-art progresses in the architecture designing of host/guest photoanodes with integrated enhancement strategies, including i) light trapping effect; ii) optimization of conductive host scaffolds; iii) hierarchical structure engineering. The challenges and prospects for the future development of host/guest nanostructured photoanodes are also presented.

Symbiotic Algae-Bacteria Dressing for Producing Hydrogen to Accelerate Diabetic Wound Healing.

Oxidative stress induced by hyperglycemia or chronic inflammation can limit diabetic wound healing, resulting in diabetic foot ulcers. Hydrogen has the potential to act as an antioxidant and scavenge reactive oxygen species, thereby attenuating inflammation in these chronic wounds. However, most of the reported H2 delivery systems for wound healing, including hydrogen gas, hydrogen-rich water, and hydrogen-rich saline, are very short-lived for the low solubility of hydrogen gas. Here, we introduce a hydrogen-producing hydrogel made of living Chlorella and bacteria within a cell-impermeable casing that can continuously produce hydrogen for 60 h. This microbe-hydrogel system can selectively reduce highly toxic •OH and ONOO- species and reduce inflammation. Additional experiments indicated that the microbe-hydrogel dressing could promote cell proliferation and diabetic wound healing by almost 50% at day 3. The symbiotic algae-bacteria hydrogel has excellent biocompatibility and reactive oxygen species scavenging features, indicating it has great promise for clinical use.

Faradaic junction and isoenergetic charge transfer mechanism on semiconductor/semiconductor interfaces.

Energy band alignment theory has been widely used to understand interface charge transfer in semiconductor/semiconductor heterojunctions for solar conversion or storage, such as quantum-dot sensitized solar cells, perovskite solar cells and photo(electro)catalysis. However, abnormally high open-circuit voltage and charge separation efficiency in these applications cannot be explained by the classic theory. Here, we demonstrate a Faradaic junction theory with isoenergetic charge transfer at semiconductor/semiconductor interface. Such Faradaic junction involves coupled electron and ion transfer, which is substantively different from the classic band alignment theory only involving electron transfer. The Faradaic junction theory can be used to explain these abnormal results in previous studies. Moreover, the characteristic of zero energy loss of charge transfer in a Faradaic junction also can provide a possibility to design a solar conversion device with a large open-circuit voltage beyond the Shockley-Queisser limit by the band alignment theory.

In Situ Determination of Polaron-Mediated Ultrafast Electron Trapping in Rutile TiO2 Nanorod Photoanodes.

Mechanistic understanding of the photogenerated charge carrier dynamics in modified semiconductor photoanodes is vital for the efficient enhancement of photoelectrochemical (PEC) water splitting. Here, an in situ femtosecond (fs)-transient absorption spectroscopy (TAS) assisted spectroelectrochemistry technique is used to probe the behavior of charge carriers in rutile TiO2 nanorod photoanodes under the different applied potentials and different density of surface polaron states that can be tuned via direct electrochemical protonation. We interpreted the background absorption with long-time decay in terms of polaron-mediated ultrafast electron trapping. The depleted surface polaron states on rutile TiO2 nanorods can trap photogenerated electrons and endow them with a long lifetime; thus, increasing the polaron state density can enhance the charge separation efficiency and the photocurrent density of the TiO2 nanorod electrode.

Extraterrestrial artificial photosynthetic materials for in-situ resource utilization.

Aerospace milestones in human history, including returning to the moon and manned Martian missions, have been implemented in recent years. Space exploration has become one of the global common goals, and to ensure the survival and development of human beings in the extraterrestrial extreme environment has been becoming the basic ability and technology of manned space exploration. For the purpose of fulfilling the goal of extraterrestrial survival, researchers in Nanjing University and the China Academy of Space Technology proposed extraterrestrial artificial photosynthesis (EAP) technology. By simulating the natural photosynthesis of green plants on the Earth, EAP converts CO2/H2O into fuel and O2 in an in-situ, accelerated and controllable manner by using waste CO2 in the confined space of spacecraft, or abundant CO2 resources in extraterrestrial celestial environments, e.g. Mars. Thus, the material loading of manned spacecraft can be greatly reduced to support affordable and sustainable deep space exploration. In this paper, EAP technology is compared with existing methods of converting CO2/H2O into fuel and O2 in the aerospace field, especially the Sabatier method and Bosch reduction method. The research progress of possible EAP materials for in-situ utilization of extraterrestrial resources are also discussed in depth. Finally, this review lists the challenges that the EAP process may encounter, which need to be focused on for future implementation and application. We expect to deepen the understanding of artificial photosynthetic materials and technologies, and aim to strongly support the development of manned spaceflight.

2D High-Entropy Hydrotalcites.

High-entropy materials (HEMs) with unique configuration and physicochemical properties have attracted intensive research interest. However, 2D HEMs have not been reported yet. To find out unique properties of combining 2D materials and HEMs, a series of 2D high-entropy hydrotalcites (HEHs) is created by coprecipitation method, including quinary, septenary, and even novenary metallic elements. It is found that the fast synthetic kinetics of coprecipitation process conquers the thermodynamically solubility limitation of different elements, which is the prerequisite condition to form HEHs. As the oxygen evolution reaction (OER) electrocatalysts, HEHs show significantly decreased apparent activation energy compared with low-entropy hydrotalcites (LEHs) due to the lattice distortion induced by the multimetallic character of HEHs. This work opens up a new avenue for the development of 2D HEMs, which broadens the family of HEMs and presents a most promising platform for exploring the unknown properties of HEMs.