Crystal facet-dependent photogenerated charge separation and surface reactions are crucial for efficient photoelectrochemical (PEC) water splitting. However, the kinetic mismatch between photogenerated hole transfer and the water oxidation reaction (WOR) can impede the PEC performance of photoanodes. Herein, uniform octadecahedral BiVO4 (O-BiVO4) single crystal photoanodes with exposed {040}, {011}, and high-reactivity {121} facets are synthesized to reveal the significance of synchronizing photogenerated hole transfer with WOR activity. The results show that the photogenerated holes preferentially accumulate on the {121} facets with excellent WOR activity. Consequently, the O-BiVO4 photoanode exhibits an impressive photocurrent density of 2.05mA/cm2 at 1.23V versus the reversible hydrogen electrode (VRHE), which is 4.4 times higher than that of decahedral BiVO4 surrounded by {040} and {011} facets. Furthermore, the PEC performance of O-BiVO4 outperforms most state-of-the-art unmodified BiVO4, attributed to the well-matched kinetic process between photogenerated holes transfer and the WOR. After loading NiFeOOH as an oxygen evolution cocatalyst, a stable photocurrent density of 4.63mA/cm2 at 1.23 VRHE is achieved. This work offers valuable insight into the relationship between semiconductor photoanode performance and the crystal facets, guiding the rational design of high-reactivity crystal facets for efficient solar energy conversion.

Synchrotron radiation monochromatic X-ray computed tomography (CT) is a powerful tool for in-situ characterization of the internal microstructure evolution in composite materials. However, prolonged X-ray irradiation during long-term in-situ studies may affect the structure and properties of material. While the effects of white beam irradiation have been widely investigated, the specific damage mechanisms and material sensitivity to monochromatic X-ray irradiation, particularly in composite materials like propellants, are not well understood. In this study, we identify the threshold irradiation time that triggers radiation damage in PBT propellant and observe the accumulation and worsening of damage over time, primarilyinitiated by ether bond cleavage, leading to radiation-induced decomposition and increased internal porosity. This resulted in a significant reduction in the mechanical strength of PBT propellant, particularly under prolonged exposure to synchrotron radiation. In contrast, the inert binder system HTPB propellant exhibited better radiation stability. Our study highlights the importance of considering both radiation-induced damage and material X-ray sensitivity when designing in-situ synchrotron radiation CT experiments for composite materials, and suggests that the development of dynamic experimental methods to further reduce the risk of radiation damage for high-reliability in-situ assessment of material properties, as well as the need for careful consideration of radiation effects in the design and safety evaluation of solid propellant systems working in extreme circumstance.

Microwave-assisted catalysis is a promising technique for enhancing catalytic reactions through selective heating, potentially leading to improved reaction rates and energy efficiency. However, understanding the complex interactions between microwave absorption and catalytic performance in composite catalysts remains a challenge. In this study, Cobalt oxide(Co3O4)/silicon carbide(SiC) composite catalysts with varying SiC content were synthesized and characterized to investigate the relationship between their microwave absorption properties and catalytic performance. Quantitative analysis revealed that SiC and Co3O4 absorb microwave energy through relaxation polarization and magnetic loss mechanisms, respectively. Increasing SiC content enhanced the dielectric and magnetic loss capabilities of the composites, with the Co3O4/SiC composite containing 10 wt% SiC (Co3O4/SiC-10) exhibiting a dielectric loss tangent of 3.87 and a minimum reflection loss of -35dB. However, higher SiC content decreased the surface chemically adsorbed oxygen, surface oxygen mobility, and benzene adsorption capacity, weakening the catalytic activity under conventional heating. The Co3O4/SiC-10 sample achieved a significantly better balance between microwave absorption and catalytic performance, significantly outperforming the original Co3O4 sample under microwave irradiation. These founding establishes a quantitative research methodology that correlates dielectric loss tangent, reflection loss, and other crucial parameters with microwave absorption performance and further catalytic properties, providing insights for the rational design of catalysts that optimize both microwave absorption and catalytic activity.

Photocatalytic reduction of carbon dioxide into sustainable green solar fuel is a promising solution to both environmental problems and energy crises.Despite extensive research to date,there are still many obstacles to achieving efficient,selective and stable CO 2 reduction.Furthermore,the use of water as an electron donor rather than a sacrificial reagent in order to achieve ΔG＞0 of the reaction is essential for ideal artificial ’photosynthesis’,but it also presents many challenges for photocatalytic reduction of CO 2 systems.In this review,we first briefly introduce the mechanism and challenges of photocatalytic reduction of CO 2 ,and then we summarize the corresponding strategies and the latest research progress according to the current problems of photocatalytic reduction of CO 2 without sacrificial reagent,such as the adjustment of band structure,the loading of cocatalysts,the construction of heterojunctions,the design of MOFs and COFs materials,etc.At last,the unsolved problems and the obstacles to industrial application in the future are summarized.

The evolution information of the condensed phase of solid propellants during combustion is crucial to mastering the behavior of solid propellants and obtaining desired characteristics. However, insight into condensed-phase microstructure and gaseous production evolution and their correlations achieved via in-situ characterization are still lacking due to the phase opacity and violent deformation of the condensed-phase region during operating conditions. Consequently, ex-situ quenched surface study has dominated this field for several decades. Herein, we demonstrate our initial work, where the subsurface condensed-phase evolution characterization is achieved via in-situ synchrotron X-ray radiography and FT-IR spec-troscopy. The obtained images show the evolution of component-specific microstructure due to the con-version of solid ingredients to gas during the thermal decomposition process. Comparatively, in-situ FT-IR spectroscopy tracks the evolved gas products. For the first time, we directly observed different evolved behaviors of the condensed-phase microstructure of two typical solid propellants using inert and en-ergetics binders, respectively, via the in-situ image technique. Such microstructure transformations are further quantitatively evaluated based on a series of imaging processing and subsequently their corre-lations with the chemical structure of different binders are also investigated via analyzing the gaseous product during degradation. Therefore, the combination of the above techniques helped study the con-densed phase of solid propellant, especially for microstructural changes under reaction conditions. We expect this methodology would be beneficial for directly understanding the subsurface microstructure evolution properties linked with related chemical reactions.(c) 2022 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

Step-scheme (S-scheme) heterojunctions in photocatalysts can provide novel and practical insight on promoting photogenerated carrier separation. The latter is critical in controlling the overall efficiency in one-step photoexcitation systems. In this study, a nanosized Bi0.6Y0.4VO4 solid solution was prepared by a coprecipitation method following with hydrothermal or calcination processes. The S-scheme heterojunction was fabricated by in-situ pressure-induced transformations of bismuth vanadate from the tetragonal zircon phase to the monoclinic scheelite phase, which led to the formation of BiVO4 nanoparticles with a diameter of approximately 5 nm on the surface of Bi0.6Y0.4VO4. Bi0.6Y0.4VO4 with S-scheme heterojunctions showed significantly enhanced photocatalytic overall water splitting activity compared with using bare Bi0.6Y0.4VO4. Characterization of the carrier dynamics demonstrated that a superior carrier separation through S-type heterojunctions might have caused the enhanced overall water splitting (OWS) activity. Surface photovoltage spectra and the results of selective photodeposition experiments indicated that the photogenerated holes mainly migrated to the BiVO4 nanoparticles in the heterojunction. This confirmed that the charge transfer route corresponds to an S-scheme rather than a type-II heterojunction mechanism under light illumination. This study presents a facile and efficient strategy to construct S-scheme heterojunctions through a pressure-induced phase transition. The results demonstrated that S-scheme junctions composed of different crystalline phases can boost the carrier separation capacity and eventually improve the photocatalytic OWS activity.

The solid solution photocatalyst plays a vital role in designing the one-step excitation water splitting system. However, the co-existence of the evolution of surface heterostructure together with the gradual formation of solid solutions makes it difficult to distinguish the inherent role of solid solution and surface structure in OWS reaction. Herein, Bi0.5Y0.5VO4 solid solution was synthesized through a fine-tuned co-precipitation procedure at room temperature, which acted as starting materials for further annealing treatment. Systematic characterizations revealed that variations in surface B-V-O domain at different temperatures induced the generation of particular heterogeneous structures in the solid solution surface. After annealing at 600 degrees C, the surface V-rich amorphous layer on Bi0.5Y0.5VO4 delivered functional electron trapping and optimized reaction dynamics, leading to enhanced OWS activity. In contrast, a nano-junction alignment formed at 800 degrees C near the surface resulted in an inappropriate band structure and poor charge dynamics, finally suppressing the OWS activity. (C) 2022 Elsevier Inc. All rights reserved.

Cobalt oxides find widespread application in energy materials as oxygen evolution catalysts (OECs) in the oxygen evolution reaction (OER) and photocatalytic overall water splitting (OWS) reaction. However, the nature of the active cobalt species, their role in these reactions, and possible commonalities remain poorly understand. Here, the impact of (redox-inert) germanium dopants on the physicochemical properties of Co3O4 nanoparticles was investigated in electrochemical oxygen evolution and photo-catalytic OWS reactions. A significant enhancement in OER performance on doping is attributed to the restructuring of spinel Co(3)O(4)to serpentine Co3Ge2(OH)(5), with the latter transforming to an oxyhydroxide active phase during OER. Combination of the p-type Co3Ge2(OH)(5) semiconductor as an OEC with an n-type Bi0.5Y0.5VO4 semiconductor doubles the photocatalytic OWS activity of the latter, resulting in H2 and O2 productivities of & SIM;175.7 and & SIM;90.1 smol/h, respectively. Formation of the composite semiconductor induces an intense internal electric field across the p-n junction, facilitating separation of photogenerated carriers and increased OWS activity, which is also validated in alternative photocatalyst, Al-doped SrTiO3. A similar transformation of serpentine Co3Ge2(OH)5 to an oxyhydroxide was not observed during OWS, indicating that Ge doping confers distinct advantages for electrochemical OER vs photocatalytic OWS.

The reconstruction during oxygen evolution reaction(OER)significantly affects the electronic and local geometry structure of metal sites in electrocatalyst.Compared with well-investigated cobalt-based mate-rials,the reconstruction of rocksalt CoO with purely Co2+in octahedral(Oh)coordination has not been revealed in detail.Herein,monolayer CoO supported on reduced graphene oxide(rGO)was synthesized via a one-pot hydrothermal strategy with calcinating in Ar atmosphere.The structure evolution of two-dimension(2D)CoO/rGO during OER was revealed by in situ X-ray absorption spectroscopy(XAS).The transition from CoO toward Co3O4 already occurred at open circuit potential,further enhanced at 1.23 V(vs.RHE).The CoOx(OH)y was determined as the active phase at 1.53 V,displaying a tetrahedral Co coordination defective spinel Co3O4 with the Co-O shell that featured the(oxy)hydroxide,not the stan-dard CoOOH.After OER,the irreversible transition from CoO to Co3O4 was observed.In contrast,in situ Raman spectra revealed a reversible amorphization process on Co3O4/rGO under operation conditions.Furthermore,this study indicated that the reconstruction behavior could be more effectively revealed by XAS using 2D materials.