Formation of Hierarchical FeCoS 2 –CoS 2 Double‐Shelled Nanotubes with Enhanced Performance for Photocatalytic Reduction of CO 2

Carbon nanotube-encapsulated Co/Co3Fe7 heterojunctions as a highly-efficient bifunctional electrocatalyst for rechargeable zinc-air batteries

In oxygen electrocatalysis, how to rationally design low-cost catalysts with reasonable structure and long-term stability is a crucial issue. Here, an in-situ growth strategy is used to construct a shaped structure encapsulating a uniformly-dispersed Co/Co3Fe7 heterojunction in nitrogen-doped carbon nanotubes (Co/Co3Fe7@NCNTs). Hollow CoFe layered-double-hydroxide prisms act as sacrifices for in-situ growth of Co/Co3Fe7 nanoparticles, which also catalyze the growth of bamboo-like NCNTs. Tubular structure not only accelerates the charge transfer through the interactions between Co and Co3Fe7, but also limits the aggregation of the particles, thereby promoting the 4e- oxygen reduction/evolution reactions (ORR/OER) kinetics and stabilizing the bifunctional activity. Co/Co3Fe7@NCNTs-800 (pyrolyzed at 800 °C) shows exceptional ORR activity (half-wave potential of 0.89 V) and methanol tolerance. Meanwhile, Co/Co3Fe7@NCNTs-800 shows a small OER overpotential of 280 mV, which increases by only 9 mV after 1000 cyclic voltammetry (CV) cycles. The outstanding bifunctionality (potential gap of 0.62 V) is ascribed to the electronic structure modulation at the Co/Co3Fe7 heterointerface. Notably, it also has a high performance as an air-cathode for rechargeable zinc-air battery, showing high power density (165 mW cm-2) and specific capacity (770.5 m Ah kg-1). This work provides a new reference for promoting the development of alloy catalysts with heterogeneous interfaces.

Novel hollow core-shell Zn0.5Cd0.5S@ZnIn2S4/MoS2 nanocages with Z-scheme heterojunction for enhanced photocatalysis of hydrogen generation

The development of low-cost and efficient metal sulfide photocatalysts through morphological and structural design is vital to the advancement of the hydrogen economy. However, metal sulfide semiconductor photocatalysts still suffer from low carrier separation and poor solar-to-hydrogen conversion efficiencies. Herein, two-dimensional ZnIn2S4 nanosheets were grown on Zn0.5Cd0.5S hollow nanocages to construct Zn0.5Cd0.5S@ZnIn2S4 hollow nanocages for the first time. Novel hollow core-shell Zn0.5Cd0.5S@ZnIn2S4/MoS2 nanocages with Z-scheme heterojunction structures were obtained by incorporating MoS2 nanosheet co-catalyst via the solvothermal method. The resulting Zn0.5Cd0.5S@ZnIn2S4/MoS2 exhibited unique structural and compositional advantages, leading to remarkable photocatalytic hydrogen evolution rates of up to 8.5 mmol·h-1·g-1 without the use of any precious metal co-catalysts. This rate was 10.6-fold and 7.1-fold higher compared to pure ZnIn2S4 and Zn0.5Cd0.5S, respectively. Moreover, the optimized Zn0.5Cd0.5S@ZnIn2S4/MoS2 photocatalyst outperformed numerous reported ZnIn2S4-based photocatalysts and some ZnIn2S4-based photocatalysts based on precious metal co-catalysts. The exceptional photocatalytic performance of Zn0.5Cd0.5S@ZnIn2S4/MoS2 can be attributed to the Z-scheme heterojunction of core-shell structure that enhanced charge carrier separation and transport, as well as the co-catalytic action of MoS2. Overall, the proposed Zn0.5Cd0.5S@ZnIn2S4/MoS2 with heterojunction structure is a promising candidate for the preparation of efficient photocatalysts for solar-to-hydrogen energy conversion.

Modulating Charge Separation of Oxygen-Doped Boron Nitride with Isolated Co Atoms for Enhancing CO2 -to-CO Photoreduction

To alleviate the greenhouse effect and address the related energy crisis, solar-driven reduction of carbon dioxide (CO2 ) to value-added products is considered as a sustainable strategy. However, the insufficient separation and rapid recombination of photogenerated charge carriers during photocatalysis greatly limit their reduction efficiency and practical application potential. Here, isolated Cobalt (Co) atoms are successfully decorated into oxygen-doped boron nitride (BN) via an in situ pyrolysis method, achieving greatly improved catalytic activity and selectivity to the carbon monoxide (CO) product. X-ray absorption fine spectroscopy demonstrates that the isolated Co atoms are stabilized by the O and N atoms with an unsaturated CoO2 N1 configuration. Further experimental investigation and theoretical simulations confirm that the decorated Co atoms not only work as the real active center during the CO2 reduction process, but also perform as the electron pump to promote the electron/hole separation and transfer, resulting in greatly accelerated reaction kinetics and improved activity. In addition, the CoO2 N1 coordination geometry is favorable to the conversion from *CO2 to *COOH, which shall be considered as a selectivity-determining step for the evolution of the CO products. The surface modulation strategy at the atomic level opens a new avenue for regulating the reaction kinetics for photocatalytic CO2 reduction.

Multilevel-Regulated Metal-Organic Framework Platform Integrating Pore Space Partition and Open-Metal Sites for Enhanced CO2 Photoreduction to CO with Nearly 100% Selectivity

Rational design and regulation of atomically precise photocatalysts are essential for constructing efficient photocatalytic systems tunable at both the atomic and molecular levels. Herein, we propose a platform-based strategy capable of integrating both pore space partition (PSP) and open-metal sites (OMSs) as foundational features for constructing high-performance photocatalysts. We demonstrate the first structural prototype obtained from this strategy: pore-partitioned NiTCPE-pstp (TCPE = 1,1,2,2-tetra(4-carboxylphenyl)ethylene, pstp = partitioned stp topology). Nonpartitioned NiTCPE-stp is constructed from six-connected [Ni3(μ3-OH)(COO)6] trimer and TCPE linker to form 1D hexagonal channels with six coplanar OMSs directed at channel centers. After introducing triangular pore-partitioning ligands, half of the OMSs were retained, while the other half were used for PSP, leading to unprecedented microenvironment regulation of the pore structure. The resulting material integrates multiple advanced properties, including robustness, wider absorption range, enhanced electronic conductivity, and high CO2 adsorption, all of which are highly desirable for photocatalytic applications. Remarkably, NiTCPE-pstp exhibits excellent CO2 photoreduction activity with a high CO generation rate of 3353.6 μmol g-1 h-1 and nearly 100% selectivity. Theoretical and experimental studies show that the introduction of partitioning ligands not only optimizes the electronic structure to promote the separation and transfer of photogenerated carriers but also reduces the energy barrier for the formation of *COOH intermediates while promoting CO2 activation and CO desorption. This work is believed to be the first example to integrate PSP strategies and OMSs within metal-organic framework (MOF) photocatalysts, which provides new insight as well as new structural prototype for the design and performance optimization of MOF-based photocatalysts.

Boosting Conductive Loss and Magnetic Coupling Based on "Size Modulation Engineering" toward Lower-Frequency Microwave Absorption

The rational design of absorber size is a promising strategy for obtaining excellent electromagnetic wave (EMW) absorption performance. However, achieving controllable tuning of the material size through simple methods is challenging and the associated EMW attenuation mechanisms are still unclear. In this study, the sizes of metal-organic frameworks (MOFs) are successfully tailored by changing the growth time and the molar ratio of iron (Fe)/organic ligands. The lateral and vertical lengths of MOFs vary in the range of 200 nm to 2 µm and 100 nm to 1 µm, respectively. Both experiments and simulations confirm that the decrease of MOF size favors the formation of more conductive networks, which is beneficial for improving the conductivity loss. Meanwhile, the micromagnetic simulation reveals that the magnetic coupling can be effectively enhanced by the decrease of MOF size, which is conducive to the improvement of magnetic loss, especially in low-frequency range. The reflection loss of Fe-based MOFs with optimized size reaches -46.4 dB at 6.2 GHz with an effective absorption bandwidth of 3.1 GHz. This work illustrates the important role of size effect in EMW dissipation and provides an effective strategy for enhancing the low-frequency EMW absorption performance.

Boosting photocatalytic conversion of formic acid to CO over P-doped CdS

In this work, NaH2PO2, Na2S2O3 and CdCl2 were used to synthesize P-doped CdS samples for the photocatalytic decomposition of formic acid to CO reaction. The CO production rates and selectivity of P-doped CdS are as high as 24.5 mmol g-1 h-1 and 92.4%, in which the rate is 7 times higher than that of the pure CdS. Multiple characterizations show that the P-doping increases the specific surface area, widens the band gap and shifts the energy band position of CdS, resulting in enhanced photocatalytic activity.

Low-Dimensional High-Entropy Alloys for Advanced Electrocatalytic Reactions

Low-dimensional high-entropy alloy (HEA) nanomaterials are widely employed as electrocatalysts for energy conversion reactions, due to their inherent advantages, including high electron mobility, rich catalytically active site, optimal electronic structure. Moreover, the high-entropy, lattice distortion, and sluggish diffusion effects also enable them to be promising electrocatalysts. A thorough understanding on the structure-activity relationships of low-dimensional HEA catalyst play a huge role in the future pursuit of more efficient electrocatalysts. In this review, we summarize the recent progress of low-dimensional HEA nanomaterials for efficient catalytic energy conversion. By systematically discussing the fundamentals of HEA and properties of low-dimensional nanostructures, we highlight the advantages of low-dimensional HEAs. Subsequently, we also present many low-dimensional HEA catalysts for electrocatalytic reactions, aiming to gain a better understanding on the structure-activity relationship. Finally, a series of upcoming challenges and issues are also thoroughly proposed as well as their future directions.

Strain-Engineering of Mesoporous Cs3 Bi2 Br9 /BiVO4 S-Scheme Heterojunction for Efficient CO2 Photoreduction

Slow charge kinetics and unfavorable CO₂ adsorption/activation strongly inhibit CO₂ photoreduction. In this study, a strain-engineered Cs₃ Bi₂ Br₉ /hierarchically porous BiVO₄ (s-CBB/HP-BVO) heterojunction with improved charge separation and tailored CO₂ adsorption/activation capability is developed. Density functional theory calculations suggest that the presence of tensile strain in Cs₃ Bi₂ Br₉ can significantly downshift the p-band center of the active Bi atoms, which enhances the adsorption/activation of inert CO₂ . Meanwhile, in situ irradiation X-ray photoelectron spectroscopy and electron spin resonance confirm that efficient charge transfer occurs in s-CBB/HP-BVO following an S-scheme with built-in electric field acceleration. Therefore, the well-designed s-CBB/HP-BVO heterojunction exhibits a boosted photocatalytic activity, with a total electron consumption rate of 70.63 µmol g^-1 h^-1 , and 79.66% selectivity of CO production. Additionally, in situ diffuse reflectance infrared Fourier transform spectroscopy reveals that CO₂ photoreduction undergoes a formaldehyde-mediated reaction process. This work provides insight into strain engineering to improve the photocatalytic performance of halide perovskite.

Interfacial built-in electric-field for boosting energy conversion electrocatalysis

The formation of a built-in electric field (BIEF) can induce electron-rich and electron-poor counterparts to synergistically modify electronic configurations and optimize the binding strengths with intermediates, thereby leading to outstanding electrocatalytic performance. Herein, a critical review regarding the concept, modulation strategies, and applications of BIEFs is comprehensively summarized, which begins with the fundamental concepts, together with the advantages of BIEF for boosting electrocatalytic reactions. Then, a systematic summary of the advanced strategies for the modulation of BIEF along with the in-detail mechanisms in its formation are also added. Finally, the applications of BIEF in driving electrocatalytic reactions and some cascade systems for illustrating the conclusive role from the induced BIEF are also systematically discussed, followed by perspectives on the future deployment and opportunity of the BIEF design.

Recent Developments and Perspectives of Cobalt Sulfide-Based Composite Materials in Photocatalysis

Photocatalysis, as an inexpensive and safe technology to convert solar energy, is essential for the efficient utilization of sustainable renewable energy sources. Earth-abundant cobalt sulfide-based composites have generated great interest in the field of solar fuel conversion because of their cheap, diverse structures and facile preparation. Over the past 10 years, the number of reports on cobalt sulfide-based photocatalysts has increased year by year, and more than 500 publications on the application of cobalt sulfide groups in photocatalysis can be found in the last three years. In this review, we initially summarize the four common strategies for preparing cobalt sulfide-based composite materials. Then, the multiple roles of cobalt sulfide-based cocatalysts in photocatalysis have been discussed. After that, we present the latest progress of cobalt sulfide in four fields of photocatalysis application, including photocatalytic hydrogen production, carbon dioxide reduction, nitrogen fixation, and photocatalytic degradation of pollutants. Finally, the development prospects and challenges of cobalt sulfide-based photocatalysts are discussed. This review is expected to provide useful reference for the construction of high-performance cobalt sulfide-based composite photocatalytic materials for sustainable solar-chemical energy conversion.

Dual cocatalysts and vacancy strategies for enhancing photocatalytic hydrogen production activity of Zn3In2S6 nanosheets with an apparent quantum efficiency of 66.20

Converting solar energy into hydrogen energy is a feasible means to solve the current energy crisis. However, developing an excellent photocatalyst with high light utilization and stability for hydrogen production remains a great challenge. In this work, CoS₂ nanoparticles as cocatalysts are growth on Zn₃In₂S₆ nanosheets with abundant sulfur vacancies for hydrogen evolution, and the optimal rate of hydrogen evolution is as high as 5.69 mmol h^-1 g^-1 in the absence of noble metal co-catalyst Pt, which is 2.87 and 2.29 times that of CoS₂/Zn₃In₂S₆ (with few sulfur vacancies) and Zn₃In₂S₆ (with rich sulfur vacancies). In addition, the hydrogen production rate of CoS₂/Zn₃In₂S₆ composite (with rich sulfur vacancies and 1 wt% Pt) is 24.17 mmol h^-1 g^-1, which is 4.25 and 1.90 times that of CoS₂/Zn₃In₂S₆ (with rich sulfur vacancies) and 1%-Pt/Zn₃In₂S₆ (with rich sulfur vacancies), respectively. The apparent quantum efficiency (AQE) of CoS₂/Zn₃In₂S₆ composite (with rich sulfur vacancies and 1 wt% Pt) reaches 66.20% under light irradiation at the wavelength of 370 nm. Above all indicate that dual cocatalysts (CoS₂ and Pt) and sulfur vacancies can promote the efficient hydrogen evolution activity of Zn₃In₂S₆ nanosheets. This work will provide new ideas and insights for the development of photocatalytic hydrogen production technology.

Hollow Heterostructured Nanocatalysts for Boosting Electrocatalytic Water Splitting

The implementation of electrochemical water splitting demands the development and application of electrocatalysts to overcome sluggish reaction kinetics of hydrogen/oxygen evolution reaction (HER/OER). Hollow nanostructures, particularly for hollow heterostructured nanomaterials can provide multiple solutions to accelerate the HER/OER kinetics owing to their advantageous merit. Herein, the recent advances of hollow heterostructured nanocatalysts and their excellent performance for water splitting are systematically summarized. Starting by illustrating the intrinsically advantageous features of hollow heterostructures, achievements in engineering hollow heterostructured electrocatalysts are also highlighted with the focus on structural design, interfacial engineering, composition regulation, and catalytic evaluation. Finally, some perspective insights and future challenges of hollow heterostructured nanocatalysts for electrocatalytic water splitting are also discussed.

Introducing Te for boosting electrocatalytic reactions

The deployment of robust catalysts for electrochemical reactions is a critical topic for energy conversion techniques. Te-based nanomaterials have attracted increasing attention for their application in electrochemical reactions due to their positive influence on the electrocatalytic performance induced by their distinctive electronic and physicochemical properties. Herein, we have summarized the recent progress on Te-based nanocatalysts for electrocatalytic reactions by primarily focusing on the positive influence of Te on electrocatalysts. Firstly, Te-based nanomaterials can serve as an ideal template for the construction of well-defined nanostructures. Secondly, Te doping can significantly modify the electronic structure of the host catalyst, thereby, leading to the optimization of binding strength with intermediates. Furthermore, the Te etching strategy can also create a high density of surface defects, thereby leading to substantial improvement in the electrocatalytic performance. Additionally, many representative Te-based nanocatalysts for electrocatalytic reactions are also summarized and systematically discussed. Finally, a conclusive and perspective discussion is also provided to provide guidance for the future development of more efficient electrocatalysts.

Mo doping and Se vacancy engineering for boosting electrocatalytic water oxidation by regulating the electronic structure of self-supported Co9Se8@NiSe

Oxygen evolution reactions (OERs) are regarded as the rate-determining step of electrocatalytic overall water splitting, which endow OER electrocatalysts with the advantages of high activity, low cost, good conductivity, and excellent stability. Herein, a facile H₂O₂-assisted etching method is proposed for the fabrication of Mo-doped ultrathin Co₉Se₈@NiSe/NF-X heterojunctions with rich Se vacancies to boost electrocatalytic water oxidation. After step-by-step electronic structure modulation by Mo doping and Se vacancy engineering, the self-standing Mo-Co₉Se₈@NiSe/NF-60 heterojunctions deliver a current density of 50 mA cm^-2 with an overpotential of 343 mV and a cell voltage of only 1.87 V at 50 mA cm^-2 for overall water splitting in 1.0 M KOH. Our study opens up the possibility of realizing step-by-step electronic structure modulation of nonprecious OER electrocatalysts via heteroatom doping and vacancy engineering.

Cation-Anion Dual Doping Modifying Electronic Structure of Hollow CoP Nanoboxes for Enhanced Water Oxidation Electrocatalysis

Tuning the electronic state of a nanocatalyst is of vital importance for elevating its catalytic performance toward oxygen evolution reaction (OER). Herein, a cation-anion dual doping strategy has been proposed for modifying the electronic structure of CoP via doping Fe and S atoms. Impressively, Fe doping has been demonstrated to be favorable for improving the carrier density of CoP to produce more hydroxyl radicals (^•OH), while S doping can further modify the electronic structure of CoP to improve the charge-transfer characteristics, thereby synergistically decreasing the energy barrier for the transformation of O* to OOH* and promoting the electrocatalytic OER performance. More importantly, the highly open nanobox structure is also beneficial for the exposure of more accessible catalytically active sites, which can substantially facilitate the electron and mass transport, leading to the superb catalytic OER performance. The successful modulation of OER performance via dual-doping strategy will pose a new strategy for designing more advanced nanocatalysts for energy-related catalysis process.

Tremella-like 2D Nickel-Copper Disulfide with Ultrahigh Capacity and Cyclic Retention for Hybrid Supercapacitors

Two-dimensional (2D) disulfides possess unique physical and chemical properties and are widely used in electronic and photoelectric devices. Tuning the composition and optimizing the structure of the disulfides are feasible approaches to designing target sulfides for hybrid supercapacitors. This work synthesizes the tremella-like nanosheet-connected (Cu_xNi_1-x)S₂ via solvothermal and sulfur-vapor vulcanization. The 2D (Cu_xNi_1-x)S₂ electrode performs a high reversible capacity (526.0 mA h g^-1 at 1 A g^-1), decent capacity retention (75.6%) at 10 A g^-1, and prolonged cyclic retention (94.4% over 15,000 cycles), which is higher than that of (Cu_xNi_1-x)O and monometallic sulfides of NiS₂ and CuS. The elevated electrochemical properties of (Cu_xNi_1-x)S₂ are attributed to the optimized composition with increased redox reaction, enlarged lattice distance, abundant active sites, and attractive electronic and ionic conductivity. Also, (Cu_xNi_1-x)S₂ and active carbon (AC) are assembled to form a hybrid supercapacitor (HSC). The (Cu_xNi_1-x)S₂//AC HSC demonstrates a maximum specific capacitance of 231.0 F g^-1 at 1 A g^-1 and a high energy density of 82.4 W h kg^-1 at a power density of 1.82 kW kg^-1. Outstanding cyclic retentions of 94.9 and 84.5% after 8000 and 10,000 cycles are also obtained. In conclusion, this result suggests a facile routine for preparing a novel 2D layer material of (Cu_xNi_1-x)S₂ with outstanding specific capacity and cycling performance for hybrid supercapacitors.

Phosphorus Tailors the d-Band Center of Copper Atomic Sites for Efficient CO2 Photoreduction under Visible-Light Irradiation

Photoreduction of CO₂ into solar fuels has received great interest, but suffers from low catalytic efficiency and poor selectivity. Herein, two single-Cu-atom catalysts with unique Cu configurations in phosphorus-doped carbon nitride (PCN), namely, Cu₁ N₃ @PCN and Cu₁ P₃ @PCN were fabricated via selective phosphidation, and tested in visible light-driven CO₂ reduction by H₂ O without sacrificial agents. Cu₁ N₃ @PCN was exclusively active for CO production with a rate of 49.8 μmol_CO  g_cat ^-1  h^-1 , outperforming most polymeric carbon nitride (C₃ N₄ ) based catalysts, while Cu₁ P₃ @PCN preferably yielded H₂ . Experimental and theoretical analysis suggested that doping P in C₃ N₄ by replacing a corner C atom upshifted the d-band center of Cu in Cu₁ N₃ @PCN close to the Fermi level, which boosted the adsorption and activation of CO₂ on Cu₁ N₃ , making Cu₁ N₃ @PCN efficiently convert CO₂ to CO. In contrast, Cu₁ P₃ @PCN with a much lower Cu 3d electron energy exhibited negligible CO₂ adsorption, thereby preferring H₂ formation via photocatalytic H₂ O splitting.

Photocatalytic reduction of low-concentration CO2 by metal-organic frameworks

Direct conversion of diluted CO₂ to value-added chemical stocks and fuels with solar energy is an energy-saving approach to relieve global warming and realize a carbon-neutral cycle. The exploration of catalysts with both efficient CO₂ adsorption and reduction ability is significant to achieving this goal. Metal-organic frameworks (MOFs) are emerging in the field of low-concentration CO₂ reduction due to their highly tunable structure, high porosity, abundant active sites and excellent CO₂ adsorption capacity. This highlight outlines the advantages of MOFs for low-pressure CO₂ adsorption and the strategies to improve the photocatalytic performance of MOF materials at low CO₂ concentrations, including the functionalization of organic ligands, regulation of metal nodes and preparation of MOF composites or derivatives. This paper aims to provide possible avenues for the rational design and development of catalysts with the ability to reduce low-concentration CO₂ efficiently for practical applications.

CdS/WO3 S-scheme heterojunction with improved photocatalytic CO2 reduction activity

The anthropogenic emission of CO₂ in the environment affected our atmosphere, which caused a rapid change in the climate. It needs to reduce the excess CO₂ from the environment to maintain sustainability and keep it green. In this work, we have fabricated a CdS decorated WO₃ nanocomposite, improving the reduction ability of CO₂ into CO and CH₄ selectively in visible light. The construction of the heterojunction improved the stability of CdS with WO₃. It synergistically resulted in ~7.7 times the higher yield of CO and 2.3 times the higher yield of CH₄ than CdS using 20 wt% CdS decorated WO₃ nanocomposite in a mixture of N,N-dimethylformamide, triethylamine, and water in a 3:1:1 ratio. The 20 wt% CdS on WO₃ nanocomposite has proven an effective and selective photocatalyst with the relative yield of methanol up to four cycles. The nanocomposite photocatalysts were analyzed using instrumental techniques, such as XRD, XPS, HR-TEM, FTIR, TGA-DTA, UV-vis, PL spectroscopy, and PEC analysis.

Hollow Nanoboxes Cu2-x S@ZnIn2 S4 Core-Shell S-Scheme Heterojunction with Broad-Spectrum Response and Enhanced Photothermal-Photocatalytic Performance

Major issues in photocatalysis include improving charge carrier separation efficiency at the interface of semiconductor photocatalysts and rationally developing efficient hierarchical heterostructures. Surface continuous growth deposition is used to make hollow Cu_2-x S nanoboxes, and then simple hydrothermal reaction is used to make core-shell Cu_2-x S@ZnIn₂ S₄ S-scheme heterojunctions. The photothermal and photocatalytic performance of Cu_2-x S@ZnIn₂ S₄ is improved. In an experimental hydrogen production test, the Cu_2-x S@ZnIn₂ S₄ photocatalyst produces 4653.43 µmol h^-1 g^-1 of hydrogen, which is 137.6 and 13.8 times higher than pure Cu_2-x S and ZnIn₂ S₄ , respectively. Furthermore, the photocatalyst exhibits a high tetracycline degradation efficiency in the water of up to 98.8%. For photocatalytic reactions, the hollow core-shell configuration gives a large specific surface area and more reactive sites. The photocatalytic response range is broadened, infrared light absorption enhanced, the photothermal effect is outstanding, and the photocatalytic process is promoted. Meanwhile, characterizations, degradation studies, active species trapping investigations, energy band structure analysis, and theoretical calculations all reveal that the S-scheme heterojunction can efficiently increase photogenerated carrier separation. This research opens up new possibilities for future S-scheme heterojunction catalyst design and development.

Facile Insights into Hydrothermal Synthesis of Ultrathin Bi4NbO8Cl Nanosheets for Efficient CO2 Photoreduction

Developing novel two-dimensional photocatalysis is an excellent strategy for high-efficiency CO₂ photoreduction. Herein, for the first time, we demonstrate a facile hydrothermal synthesis method to construct ultrathin Bi₄NbO₈Cl nanosheets using tartaric acid as a complexing agent, which can restrain the speed of nucleation. The ultrathin Bi₄NbO₈Cl nanosheets exhibit excellent catalytic activity of CO and CH₄ production (10.84 and 4.45 μmol g^-1 h^-1), which are up to 1.9 and 1.4 times higher than those of the bulk Bi₄NbO₈Cl, respectively. Photoelectric experiments and mechanism analysis systematically show that the as-obtained enhanced performance should be attributed to the formation of ultrathin Bi₄NbO₈Cl nanosheets, and charge separation and migration are significantly boosted. Therefore, this ultrathin Bi₄NbO₈Cl structure has provided new insights into the controllable preparation of ultrathin nanosheet photocatalysts to effectively improve the catalytic performance.

Directing the Architecture of Surface-Clean Cu2O for CO Electroreduction

Tailoring the morphology of nanocrystals is a promising way to enhance their catalytic performance. In most previous shape-controlled synthesis strategies, surfactants are inevitable due to their capability to stabilize different facets. However, the adsorbed surfactants block the intrinsic active sites of the nanocrystals, reducing their catalytic performance. For now, strategies to control the morphology without surfactants are still limited but necessary. Herein, a facile surfactant-free synthesis method is developed to regulate the morphology of Cu₂O nanocrystals (e.g., solid nanocube, concave nanocube, cubic framework, branching nanocube, branching concave nanocube, and branching cubic framework) to enhance the electrocatalytic performance for the conversion of CO to n-propanol. Specifically, the Cu₂O branching cubic framework (BCF-Cu₂O), which is difficult to fabricate using previous surfactant-free methods, is fabricated by combining the concentration depletion effect and the oxidation etching process. More significantly, the BCF-Cu₂O-derived catalyst (BCF) presents the highest n-propanol current density (-0.85 mA cm^-2) at -0.45 V versus the reversible hydrogen electrode (V_RHE), which is fivefold higher than that of the surfactant-coated Cu₂O nanocube-derived catalyst (SFC, -0.17 mA cm^-2). In terms of the n-propanol Faradaic efficiency in CO electroreduction, that of the BCF exhibits a 41% increase at -0.45 V_RHE as compared with SFC. The high catalytic activity of the BCF that results from the clean surface and the coexistence of Cu(100) and Cu(110) in the lattice is well-supported by density functional theory calculations. Thus, this work presents an important paradigm for the facile fabrication of surface-clean nanocrystals with an enhanced application performance.

Fabrication of 2H/3C-SiC heterophase junction nanocages for enhancing photocatalytic CO2 reduction

The morphology and structure of photocatalyst play an important role in photocatalytic activity. SiC semiconductor is considered as a promising material for the photocatalytic CO₂ reduction due to its negative conduction band position. Herein, SiC nanocages is creatively synthesized by simple low-temperature molten-salt-mediated magnesiothermic reduction method with using SiO₂ as template. The morphology and phase composition of SiC nanocages can be controlled by magnesium dosage and reaction temperature. The 2H and 3C crystal phase in SiC nanocage can form heterophase junctions uniformly to effectively accelerate the photogenerated electron transfer, and plays a key role in improving the photocatalytic activity of 2H/3C-SiC samples. The optimal SiC nanocage sample possesses a CO generation rate of 4.68 μmol g^-1h^-1 for photocatalytic CO₂ reduction, which is 3.25 times higher than that of commercial SiC.

Trimetallic Sulfide Hollow Superstructures with Engineered d-Band Center for Oxygen Reduction to Hydrogen Peroxide in Alkaline Solution

High-performance transition metal chalcogenides (TMCs) as electrocatalysts for two-electron oxygen reduction reaction (2e-ORR) in alkaline medium are promising for hydrogen peroxide (H₂ O₂ ) production, but their synthesis remains challenging. In this work, a titanium-doped zinc-cobalt sulfide hollow superstructure (Ti-ZnCoS HSS) is rationally designed as an efficient electrocatalyst for H₂ O₂ electrosynthesis. Synthesized by using hybrid metal-organic frameworks (MOFs) as precursors after sulfidation treatment, the resultant Ti-ZnCoS HSS exhibits a hollow-on-hollow superstructure with small nanocages assembled around a large cake-like cavity. Both experimental and simulation results demonstrate that the polymetallic composition tailors the d-band center and binding energy with oxygen species. Moreover, the hollow superstructure provides abundant active sites and promotes mass and electron transfer. The synergistic d-band center and superstructure engineering at both atomic and nanoscale levels lead to the remarkable 2e-ORR performance of Ti-ZnCoS HSS with a high selectivity of 98%, activity (potential at 1 mA cm^-2 of 0.774 V vs reversible hydrogen electrode (RHE)), a H₂ O₂ production rate of 675 mmol h^-1 g_cat ^-1 , and long-term stability in alkaline condition, among the best 2e-ORR electrocatalysts reported to date. This strategy paves the way toward the rational design of polymetallic TMCs as advanced 2e-ORR catalysts.

Energy-Saving Hydrogen Production by Seawater Electrolysis Coupling Sulfion Degradation

Electrolysis of costless and infinite seawater is a promising way toward grid-scale hydrogen production without causing freshwater stress. Practical potential of this technology, however, is hindered by low energy efficiency and anode corrosion by the detrimental chlorine chemistry in seawater in addition to unaffordable electricity expense. Herein, energy-saving hydrogen production is reported by chlorine-free seawater splitting coupling sulfion oxidation. It yields hydrogen at a low cell voltage of 0.97 V, cutting the electricity consumption to 2.32 kWh per m³ H₂ at 300 mA cm^-2 . Compared to alkaline water electrolysis, the energy expense is primarily saved by 60% with 50% lower energy equivalent input. Benefiting from the ultralow cell voltage, the hazardous chlorine chemistry is fully avoided without anode corrosion regardless of Cl^- crossover. Meanwhile, it also allows fast degradation of S^2- pollutant from the water body to value-added sulfur with 80% efficiency, for further reducing hydrogen cost and protection of the ecosystem. Connecting such a hybrid seawater electrolyzer to a commercial solar cell can harvest the hydrogen from seawater with better sustainability. This work may offer new opportunities for low-cost hydrogen production from the unlimited ocean resources with environmental protection.

Ultrathin Nanosheet Assembled Multishelled Superstructures for Photocatalytic CO2 Reduction

Solar-driven conversion of CO₂ is considered an efficient way to tackle the energy and environmental crisis. However, the photocatalytic performance is severely restricted due to the insufficient accessible active sites and inhibited electron transfer efficiency. This work demonstrates a general in situ topological transformation strategy for the integration of uniform Co-based species to fabricate a series of multishelled superstructures (MSSs) for CO₂ photocatalytic conversion. Thorough characterizations reveal the obtained MSSs feature ultrathin Co-based nanosheet assembled polyhedral structures with tunable shell numbers, inner cavity sizes, and compositions. The superstructures increase the spatial density of Co-based active sites while maintaining their high accessibility. Further, the ultrathin nanosheets also facilitate the transfer of photogenerated electrons. As a result, the ZnCo bimetallic hydroxide featuring an ultrathin nanosheet assembled quadruple-shell hollow structure (ZnCo-OH QUNH) exhibits high photocatalytic efficiency toward CO₂ reduction with a CO evolution rate of 134.2 μmol h^-1 and an apparent quantum yield of 6.76% at 450 nm. The quasi in situ spectra and theoretical calculations disclose that Co sites in ZnCo-OH QUNH act as highly active centers to stabilize the COOH* intermediate, while Zn species play the role of adsorption sites for the [Ru(bpy)₃]²⁺ molecules.

Rational-Designed Principles for Electrochemical and Photoelectrochemical Upgrading of CO2 to Value-Added Chemicals

The chemical transformation of carbon dioxide (CO₂ ) has been considered as a promising strategy to utilize and further upgrade it to value-added chemicals, aiming at alleviating global warming. In this regard, sustainable driving forces (i.e., electricity and sunlight) have been introduced to convert CO₂ into various chemical feedstocks. Electrocatalytic CO₂ reduction reaction (CO₂ RR) can generate carbonaceous molecules (e.g., formate, CO, hydrocarbons, and alcohols) via multiple-electron transfer. With the assistance of extra light energy, photoelectrocatalysis effectively improve the kinetics of CO₂ conversion, which not only decreases the overpotentials for CO₂ RR but also enhances the lifespan of photo-induced carriers for the consecutive catalytic process. Recently, rational-designed catalysts and advanced characterization techniques have emerged in these fields, which make CO₂ -to-chemicals conversion in a clean and highly-efficient manner. Herein, this review timely and thoroughly discusses the recent advancements in the practical conversion of CO₂ through electro- and photoelectrocatalytic technologies in the past 5 years. Furthermore, the recent studies of operando analysis and theoretical calculations are highlighted to gain systematic insights into CO₂ RR. Finally, the challenges and perspectives in the fields of CO₂ (photo)electrocatalysis are outlined for their further development.

Dual-Functional Photocatalysis for Cooperative Hydrogen Evolution and Benzylamine Oxidation Coupling over Sandwiched-Like Pd@TiO2 @ZnIn2 S4 Nanobox

Photocatalytic hydrogen evolution (PHE) over semiconductor photocatalysts is usually constrained by the limited light-harvesting and separation of photogenerated electron-hole pairs. Most of the reported systems focusing on PHE are facilitated by consuming the photoinduced holes with organic sacrificial electron donors (SEDs). The introduction of the SEDs not only causes the environmental problem, but also increases the cost of the reaction. Herein, a dual-functional photocatalyst is developed with the morphology of sandwiched-like hollowed Pd@TiO₂ @ZnIn₂ S₄ nanobox, which is synthesized by choosing microporous zeolites with sub-nanometer-sized Pd nanoparticles (Pd NPs) embedded as the sacrificial templates. The ternary Pd@TiO₂ @ZnIn₂ S₄ photocatalyst exhibits a superior PHE rate (5.35 mmol g^-1 h^-1 ) and benzylamine oxidation conversion rate (>99%) simultaneously without adding any other SEDs. The PHE performance is superior to the reported composites of TiO₂ and ZnIn₂ S₄ , which is attributed to the elevated light capture ability induced by the hollow structure, and the enhanced charge separation efficiency facilitated by the ultrasmall sized Pd NPs. The unique design presented here holds great potential for other highly efficient cooperative dual-functional photocatalytic reactions.

Emerging Stacked Photocatalyst Design Enables Spatially Separated Ni(OH)2 Redox Cocatalysts for Overall CO2 Reduction and H2 O Oxidation

Construction of photocatalytic systems with spatially separated dual cocatalysts is considered as a promising route to modulate charge separation/transfer, promote surface redox reactivities, and prevent unwanted reverse reactions. However, past efforts on the loading of spatially separated double-cocatalysts are limited to hollow structured semiconductors with inner/outer surface and monocrystalline semiconductors with different exposed facets. To overcome this limitation, herein, enabled by a unique stacked photocatalyst design, a facile and versatile strategy for spatial separation of redox cocatalysts on various semiconductors without structural and morphological restriction is demonstrated. The smart design begins with the deposition of light-harvesting semiconductors on reduced graphene oxide (rGO) nanosheets, followed with the coverage of Ni(OH)₂ outer layer. The ternary photocatalysts exhibit superior activities and stabilities of H₂ O oxidation and selective CO₂ -to-CO reduction, remarkably surpassing other counterparts. The origin of the enhanced performance is attributed to the synergistic interplay of rGO@Ni(OH)₂ reduction cocatalysts surrounding the semiconductors and Ni(OH)₂ oxidation cocatalysts directly supported by the semiconductors, which mitigates the charge recombination, supplies highly active and selective sites for overall reactions, and preserves the semiconductors from photocorrosion. This work presents a new approach to regulating the position of dual cocatalysts and ameliorating the net efficiency of photoredox catalysis.

Hierarchical CuS@ZnIn2S4 Hollow Double-Shelled p-n Heterojunction Octahedra Decorated with Fullerene C60 for Remarkable Selectivity and Activity of CO2 Photoreduction into CH4

In this work, a hollow double-shelled architecture, based on n-type ZnIn₂S₄ nanosheet-coated p-type CuS hollow octahedra (CuS@ZnIn₂S₄ HDSOs), is designed and fabricated as a p-n heterojunction photocatalyst for selective CO₂ photoreduction into CH₄. The resulting hybrids provide rich active sites and effective charge migration/separation to drive CO₂ photoreduction, and meanwhile, CO detachment is delayed to increase the possibility of eight-electron reactions for CH₄ production. As expected, the optimized CuS@ZnIn₂S₄ HDSOs manifest a CH₄ yield of 28.0 μmol g^-1 h^-1 and a boosted CH₄ selectivity up to 94.5%. The decorated C₆₀ both possesses high electron affinity and improves catalyst stability and CO₂ adsorption ability. Thus, the C₆₀-decorated CuS@ZnIn₂S₄ HDSOs exhibit the highest CH₄ evolution rate of 43.6 μmol g^-1 h^-1 and 96.5% selectivity. This work provides a rational strategy for designing and fabricating efficient heteroarchitectures for CO₂ photoreduction.