Selenization Reaction Research Articles

NiMOF-Derived MoSe2/NiSe Hollow Nanoflower Structures as Electrocatalysts for Hydrogen Evolution Reaction in Alkaline Medium.

Metal-organic frameworks (MOFs) are crystalline porous materials for storage and energy conversion applications with three-dimensional pore structure, high porosity, and specific surface area, which are widely utilized in electrocatalysis. Herein, MoSe2/NiSe composites were synthesized by selenization reaction using NiMOF as the precursor. The composites were hollow nanoflower structures with a synergistic effect between MoSe2 and NiSe to promote rapid electron transfer, which exhibited good hydrogen evolution reaction performance in an alkaline medium. At a current density of 10 mA/cm2, the HER overpotential reaches 80 mV, the Tafel slope is 33.86 mV/dec, and the material has good stability, with polarization curves remaining essentially unchanged after 3000 cycles. These results indicate that the method has a promising application in the preparation of efficient and sustainable catalysts for hydrogen production in alkaline medium.

Optimization of Selenization Condition for Efficiency CIGSe Solar Cells Based on Postselenization of CuInGa Precursors.

The degree of selenization of the CIGSe absorbers is controlled by regulating the parameters of the selenization reaction. The structure, element distribution, phase composition of the CIGSe absorbers, and the performances of the solar cells with different selenization degrees are studied. Insufficient selenization will lead to residual Cu2Se phase on the surface and insufficient Na diffusion, which will affect the VCu+ on the surface and the recombination at the front interface. However, excessive selenization will make the MoSe2 layer thicken at the back interface of the CIGSe/Mo, resulting in the increase of the series resistance and the enhancement of the recombination at the back interface. The appropriate selenization degree is conducive to inhibiting the recombination at the front and back interfaces. Improved device performances can be obtained by optimizing the selenization degree of the absorbers.

Revealing the Effect of Anion Regulation in NiCo2X4 (X = O, S, Se, Te) on Photoassisted Methanol Electrocatalytic Oxidation.

Designing nonprecious metal anode catalysts for photoassisted direct methanol fuel cells (PDMFCs) remains a challenge. As a semiconductor catalyst with a spinel structure, NiCo2O4 has good methanol catalytic oxidation activity and photocatalytic activity, making it a highly promising anode non-noble metal catalyst for PDMFCs. However, compared with the noble metal catalyst, the photoelectrocatalytic activity remained to be improved. In this report, an anion regulation strategy was adopted to improve the photoassisted methanol electrocatalytic activity. Using a CoNi-Aspartic (CoNi-Asp) nanorod as the precursor, the anion-regulated NiCo2X4 (X = O, S, Se, Te) was prepared by oxidation, sulfuration, selenization, and telluridation reactions. The regulation of anions and their effects on the electronic structure, intermediate product, and photoelectric catalytic performance of NiCo2X4 (X= O, S, Se, Te) was systematically discussed. Photoelectrochemical characterization and adsorption energy of •OH revealing the volcano-like correlation between the anion in NiCo2X4 (X = O, S, Se, Te) and their photoelectrocatalytic performance. The narrowest band gap (2.239 eV), the highest •OH adsorption energy (-3.32 eV), and the highest ratio of Co3+/Co2+ (2.19) ensure the best photoelectric catalytic performance of NiCo2S4, under the visible light irradiation, the photoresponse current density was 1.9 A g-1, the current density at 0.6 V was up to 21.9 A g-1. After 9 h of stability testing, the current retention rate was 80%. This report sheds an idea for the rational design of non-noble anode catalysts for PDMFCs.

Thickness dependence of microstructure and thermoelectric performance in Ag2Se films

With the increasing demand for energy autonomy in electronic systems, the research on thin-film-based energy harvesting devices has garnered significant attention. In this work, Ag2Se films with varying thicknesses on quartz glass substrates were fabricated using the magnetron sputtering technique and a straightforward selenization reaction. Charge transport and thermoelectric performance of these films were investigated in the low-temperature range of 300 K to 400 K. Considerable high room-temperature power factor (>2000 μW m-1 K-2) was achieved as the thickness of films exceeded 1000 nm, attributed to the favorable orientation and crystallization. A 5-leg thermoelectric prototype was assembled with 1600 nm-thickness Ag2Se film because of its highest power factor of 2530 μW m-1 K-2 at 300 K. Maximum output power density of 29.8 W m-2 and 87.7 W m-2 were obtained at the temperature difference of 30 K and 50 K respectively, surpassing the majority of the previous reports.

N-doped one-dimensional carbon framework embedded with CoSe2 nanoparticles as superior electrode for advanced sodium ion storage

Cobalt selenide (CoSe2) is acknowledged as a negative electrode material for sodium-ion batteries (SIBs) due to its high theoretical capacity. However, the significant volume change and inadequate electrochemical performance during charge and discharge processes have limited its practical use in batteries. In this investigation, a straightforward and practical electrospinning method combined with selenization reaction was utilized to fabricate CoSe2 nanoparticles enclosed in nitrogen-doped carbon nanofibers with a three-dimensional self-supporting network structure (CoSe2/N-PCNFs).The CoSe2/N-PCNFs electrode has self-supporting and high conductivity properties, as an anode material for sodium-ion batteries, the discharge capacity of the composite material can reach 450.1 mAh/g after 100 cycles at a current density of 0.2 A/g, and can still maintain a large discharge capacity of 396.9 mAh/g after 500 cycles at a high current density of 1 A/g. The outstanding electrochemical performance is mainly attributed to the superior specific surface area, controllable porous structure, and high pore volume of CoSe2/N-PCNFs Experimental and density functional theory calculations both indicate that the heterojunction interface between CoSe2 and nitrogen-doped carbon can not only promote the adsorption of Na+, but also facilitate electron transfer to significantly improve the rate capability of the material.

Trace Iron-Doped Nickel-Cobalt selenide with rich heterointerfaces for efficient overall water splitting at high current densities

Developing bifunctional electrocatalysts based on non-precious metals for overall water splitting, while maintaining high catalytic activity and stability under high current densities, remains challenging. Herein, we successfully constructred trace iron-doped nickel–cobalt selenide with abundant CoSe2 (210)-Ni3Se4 (202) heterointerfaces via a simple one-step selenization reaction. The synthesized Fe-NiCoSex/NCFF (NCFF stands for nickel–cobalt-iron foam) exhibits outstanding hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) activity with low overpotentials of 328 mV for HER and 345 mV for OER at a high current density of 1000 mA cm−2, while maintaining stability for over 20 h. Additionally, the Fe-NiCoSex/NCFF exhibits the lowest Tafel slope values for both HER (33.7 mV dec-1) and OER (55.92 mV dec-1), indicating the fastest kinetics on its surface. The Fe-NiCoSex/NCFF features uniformly distributed micrometer-sized selenide particles with dense nanowires on their surface, providing a large reactive surface area and abundant active sites. Moreover, X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) analyses reveal that the catalyst is composed of nickel, cobalt, and iron, forming micrometer-sized particles with both crystalline and amorphous phases, thereby enhancing HER and OER performance under high current density. Density functional theory (DFT) calculations demonstrate that the heterostructure CoSe2 (210)-Ni3Se4 (202), with high electron density and suitable adsorption capacity for reaction intermediates, and low energy barriers for HER (−0.384 eV) and OER (ΔG1st: 0.243 eV, ΔG2nd: 0.376 eV), serves as an active center for both HER and OER.

Constructing Cu9S5@CuSe heterostructures under microwave irradiation for rechargeable magnesium batteries

Copper chalcogenides are believed as the prospective cathode materials for rechargeable magnesium batteries. However, their practical application is seriously restricted by slow diffusion and reaction kinetics due to the large charge/radius ratio of divalent Mg2+ ions. Herein, a simple two-step microwave-assisted synthesis method is rationally developed to construct Cu9S5@CuSe heterostructures as the capable cathode materials for rechargeable magnesium batteries. Two-dimensional CuSe nanosheets are vertically grown on the surface of single-crystal Cu9S5 substrate through selenation reaction under microwave irradiation to form the mixed-dimensional heterostructures. Electrochemical measurements reveal that the as-synthesized Cu9S5@CuSe heterostructures show high reversible capacity of 240 mAh g−1 and good long-term cyclic stability with approximate 0.013 % capacity decay per cycle at 500 mA g−1 within 1000 cycles. Furthermore, the obviously enhanced rate capability can be achieved in comparison with that of single-crystal Cu9S5 substrate and CuSe nanoparticles. Ex-situ X-ray photoelectron spectroscopy and X-ray diffraction characterizations reveal favourable electrochemical conversion reaction over the Cu9S5@CuSe heterostructure cathode. The superior electrochemical properties are attributed to the optimized diffusion kinetics within the unique heterostructure. This research offers a valuable strategy to develop high-performance cathode materials with favourable kinetics for magnesium batteries.

Segmented Control of Selenization Environment for High-Quality Cu2ZnSn(S,Se)4 Films Toward Efficient Kesterite Solar Cells.

High-crystalline-quality absorbers with fewer defects are crucial for further improvement of open-circuit voltage (VOC) and efficiency of Cu2ZnSn(S,Se)4 (CZTSSe) solar cells. However, the preparation of high-quality CZTSSe absorbers remains challenging due to the uncontrollability of the selenization reaction and the complexity of the required selenization environment for film growth. Herein, a novel segmented control strategy for the selenization environment, specifically targeting the evaporation area of Se, to regulate the selenization reactions and improve the absorber quality is proposed. The large evaporation area of Se in the initial stage of the selenization provides a great evaporation and diffusion flux for Se, which facilitates rapid phase transition reactions and enables the attainment of a single-layer thin film. The reduced evaporation area of Se in the later stage creates a soft-selenization environment for grain growth, effectively suppressing the loss of Sn and promoting element homogenization. Consequently, the mitigation of Sn-related deep-level defects on the surface and in the bulk induced by element imbalance is simultaneously achieved. This leads to a significant improvement in nonradiative recombination suppression and carrier collection enhancement, thereby enhancing the VOC. As a result, the CZTSSe device delivers an impressive efficiency of 13.77% with a low VOC deficit.

Enhanced charge separation of Cu-BTC@CuSe@TiO2 hollow octahedrons for efficient CO2 photoreduction with superior CO selectivity

Solar-driven photocatalytic conversion of CO2 into high-value-added fuels has attracted widespread attention. However, the relatively low conversion efficiency and product yield severely limited photocatalytic applications. In this work, binary Cu-BTC@TiO2 catalysts with adjustable inner cavity were prepared using copper-based metal organic framework (Cu-BTC) octahedrons as substrate via a solvothermal reaction. In this process, the inner Cu-BTC octahedrons can be controllably etched into a hollow octahedral structure in the presence of HF. Subsequently, the Cu-BTC@CuSe@TiO2 hollow octahedrons (HOs) were fabricated by selenization reaction and exhibited various properties such as abundant active sites for CO2 adsorption and reduction reactions, shortened charge transfer distance to prevent electron-hole recombination, and internal reflection/scattering effects to improve solar light utilization. Moreover, the formed dual p-n heterostructures between p-type CuSe and n-type semiconductors (Cu-BTC and TiO2) effectively promote spatial separation and migration of charge carriers. The synergistic effect of these advantages makes the optimized Cu-BTC@CuSe@TiO2 HO catalyst exhibit remarkable CO2 photoreduction performance with a CO production rate of 72.3 μmol h−1 g−1 and near 100 % selectivity. This work opens a new pathway for designing highly active photocatalysts with excellent product selectivity.

Achieving high open-circuit voltage in efficient kesterite solar cells via lanthanide europium ion induced carrier lifetime enhancement

Short carrier lifetimes is a key challenge limiting the open-circuit voltage (VOC) and power conversion efficiency (PCE) of kesterite Cu2ZnSn(S,Se)4 (CZTSSe) solar cells. In this work, for the first time, lanthanide europium (Eu) ions have been introduced into Ag-incorporated CZTSSe absorber layer, which can modify the selenization reaction pathway during the initial selenization process, leading to high-quality (Ag, Eu)-CZTSSe absorber with large compact crystal grains and benign surface potential fluctuations. This innovative absorber engineering can also optimize defects dynamics with less detrimental defects and defects-assisted non-radiative recombination. Thus, significantly enhanced minority carrier lifetimes from 0.97 to 3.15 ns can be achieved, representing one of the top values among various bulk and/or interface engineering treated CZTSSe. The champion CZTSSe thin-film solar cell exhibits an impressive VOC of 545.6 mV, accompanied with a stimulating increase in PCE from 10.68% to 13.30%. These findings underscore the potential of lanthanide cation doping to drive significant advancements in CZTSSe photovoltaic technology, and therefore promoting its further development and future applications.

NiSe2/CeO2 catalysts from Ce-UiO-66 metal-organic skeletons and their electrocatalytic oxidation of methanol, urea and glycerol.

Hydrogen is a viable alternative energy source to fossil fuels. In order to manufacture enough hydrogen to meet the needs of social growth, finding an alternate energy source that is more effective is essential. Electrochemical water cracking is a more appropriate method for producing hydrogen. The methanol oxidation reaction (MOR), urea oxidation reaction (UOR) and glycerol oxidation reaction (GOR) can be used to replace the anodic oxygen evolution reaction (OER) and indirectly accelerate the hydrogen evolution reaction (HER), which has the advantages of saving energy and reducing environmental pollution. In this study, Ni/CeO2 catalysts were prepared by thermal annealing of MOFs (Ce-UiO-66) containing nickel species and NiSe2/CeO2 nanocrystalline catalysts were obtained through the selenation reaction at different temperatures. The NiSe2/CeO2-450 °C catalysts exhibited superior catalytic performance for the MOR, UOR, and GOR. The MOR showed a peak current density of roughly 186.68 mA cm-2 and a low oxidation potential of around 1.34 V. Similarly, the UOR demonstrated a peak current density of approximately 142.28 mA cm-2 and a low oxidation potential of around 1.32 V. Furthermore, the GOR exhibited a peak current density of approximately 82.56 mA cm-2 and a low oxidation potential of around 1.37 V. NiSe2/CeO2-450 °C could improve electrocatalytic performance for the MOR, UOR, and GOR, which is attributed to the more active sites that were exposed as a result of utilizing MOFs (Ce-UiO-66) as a precursor. Additionally, selenation increased the ability to transfer electrons. This research is crucial for the production of inexpensive, easily accessible transition metals in place of expensive noble metals, for the reduction of wastewater pollution from methanol and urea, and for the creation of effective anodic oxidation electrocatalysts.

Regulating Hetero-Nucleation Enabling Over 14% Efficient Kesterite Solar Cells.

Developing well-crystallized light-absorbing layers remains a formidable challenge in the progression of kesterite Cu2ZnSn(S,Se)4 (CZTSSe) solar cells. A critical aspect of optimizing CZTSSe lies in accurately governing the high-temperature selenization reaction. This process is intricate and demanding, with underlying mechanisms requiring further comprehension. This study introduces a precursor microstructure-guided hetero-nucleation regulation strategy for high-quality CZTSSe absorbers and well-performing solar cells. The alcoholysis of 2-methoxyethanol (MOE) and the generation of high gas-producing micelles by adding hydrogen chloride (HCl) as a proton additive into the precursor solution are successfully suppressed. This tailored modification of solution components reduces the emission of volatiles during baking, yielding a compact and dense precursor microstructure. The reduced-roughness surface nurtures the formation of larger CZTSSe nuclei, accelerating the ensuing Ostwald ripening process. Ultimately, CZTSSe absorbers with enhanced crystallinity and diminished defects are fabricated, attaining an impressive 14.01% active-area power conversion efficiency. The findings elucidate the influence of precursor microstructure on the selenization reaction process, paving a route for fabricating high-quality kesterite CZTSSe films and high-efficiency solar cells.

Interface Engineering of Heterogeneous NiSe2‐CoSe2@C@MoSe2 for High‐Efficient Electromagnetic Wave Absorption

AbstractOptimization of components and micromorphology regulation are shown to be effective in boosting electromagnetic wave absorption (EMWA). One approach to achieve this enhancement is by utilizing the polarization effects of heterogeneous interfaces. Herein, NiSe2‐CoSe2@C@MoSe2 composites derived from NiCo‐MOF‐74 are fabricated via a facile selenization reaction and subsequent hydrothermal method. By varying the mass ratios of NiSe2‐CoSe2@C and MoSe2, a series of NiSe2‐CoSe2@C@MoSe2 composites with hierarchical flower‐like core–shell structures are obtained. The EMWA properties of the composites display a trend of initially increasing and then decreasing with the increasing content of MoSe2. Interestingly, when the mass ratio of NiSe2‐CoSe2@C and MoSe2 is 3:2, the minimum reflection loss (RL) value is −50.10 dB and an effective absorption bandwidth (RL< −10 dB) value can reach 4.80 GHz (13.20–18.00 GHz). The remarkable EMWA capability can be ascribed to the synergy effects of conductive loss, polarization loss, and suitable impedance matching. This work establishes a new pathway for the synthesis of transition metal dichalcogenides‐based composites, which hold great promise as high‐performance materials for EMWA applications.

Controllable Oxygen‐Incorporated 2D‐SnSe2 Layered Thin Film by Plasma‐Assisted Selenization Process with Enhanced NO2 Gas Sensitivity and Improved Humidity Stability

AbstractHerein, oxygen‐incorporated 2D‐SnSe2 layered films are successfully fabricated by a plasma‐assisted selenization process. The oxygen concentrations inside the 2D‐SnSe2 layered film are controllable by controlling the proportion of hydrogen in the mixed gas of nitrogen and hydrogen during the plasma‐assisted selenization reaction. Oxygen atoms mainly exist in the form of the incorporated oxygen in the 2D‐SnSe2 layered film with an exceedingly small grain size of SnO2, which significantly increases the total interface area of the SnO2/SnSe2. Significant enhancement of the gas response to NO2 (709% under 100 ppb NO2) is reached when the proportion of hydrogen during the plasma‐assisted selenization process is 25%, thus showing excellent sensitivity and selectivity. Moreover, the sensor also demonstrated excellent stability under an increase in relative humidity. It is verified that the response will not significantly decrease when the relative humidity is below 90%. The obtained results demonstrate that oxygen‐incorporated 2D‐SnSe2 layered film with excellent commercial potential, is a highly suitable candidate for next‐generation gas sensors.

Controlling Selenization Equilibrium Enables High-Quality Kesterite Absorbers for Efficient Solar Cells

Kesterite Cu2ZnSn(S, Se)4 is considered one of the most competitive photovoltaic materials due to its earth-abundant and nontoxic constituent elements, environmental friendliness, and high stability. However, the preparation of high-quality Kesterite absorbers for photovoltaics is still challenging for the uncontrollability and complexity of selenization reactions between metal element precursors and selenium. In this study, we propose a solid-liquid/solid-gas (solid precursor and liquid/vapor Se) synergistic reaction strategy to precisely control the selenization process. By pre-depositing excess liquid selenium, we provide the high chemical potential of selenium to facilitate the direct and rapid formation of the Kesterite phase. The further optimization of selenium condensation and subsequent volatilization enables the efficient removal of organic compounds and thus improves charge transport in the absorber film. As a result, we achieve high-performance Kesterite solar cells with total-area efficiency of 13.6% (certified at 13.44%) and 1.09 cm2-area efficiency of 12.0% (certified at 12.1%).

Hierarchical Co0.6Mn0.4Se@CoMo layered double hydroxide ultra-thin nanosheet for high performance hybrid supercapacitor

Designing the novel electrode materials with compositing diverse active components and unique microstructures is an effective strategy to enhance the energy storage capacity of supercapacitors. In this work, the hierarchical composite Co0.6Mn0.4Se@CoMo-LDH, which consists of Co0.6Mn0.4Se nanosheets and CoMo-LDH, is grown directly on nickel foam by hydrothermal reaction, solvothermal selenization reaction and electrodeposition. The prepared material has unique hierarchical interconnected nanosheets, which not only increases the contact area with the electrolyte and enhances the electron transfer ability, but also enables the high capacity through the interaction between active materials. Benefiting from these advantages, the prepared material shows a high specific capacity of 1405.2 C g−1 (at current density of 1 A g−1) and an excellent capacity retention of 88.2% after 10000 cycles. Moreover, the hybrid supercapacitor assembled by Co0.6Mn0.4Se@CoMo-LDH and active carbon achieves a high energy density of 71.4 Wh kg−1 at the power density of 1.13 kW kg−1. Meanwhile, the device shows a cycle performance of 106.2% over 10000 cycles. Because of the superior electrochemical performance, Co0.6Mn0.4Se@CoMo-LDH composites electrode has a tremendous potential in upcoming energy storage technologies.

Isoselenazole Synthesis by Rh-Catalyzed Direct Annulation of Benzimidates with Sodium Selenite

Organoselenium compounds have attracted significant research interest because of their potent therapeutic activities and indispensable applications in the organic chemistry field. The selenation reactions conventionally rely on the use of sensitive Se reagents; thus, new synthetic methods with improved efficiency and operational simplicity have recently been of particular interest. In this manuscript, we report a Rh-catalyzed direct selenium annulation using tractable sodium selenite (Na2SeO3) as the limiting reagent. The selenite species was converted to highly electrophilic SeO(OBz)2 in situ upon treatment with Bz2O, thereby undergoing C–H/N–H double nucleophilic selenation. A series of benzimidates successfully underwent selenation under mild reaction conditions to afford isoselenazole derivatives.

Epitaxial growth of Cu2-xSe on Cu (220) crystal plane as high property anode for sodium storage

Three-dimentional (3D) transition metal selenides with sufficient channels could produce significant superiority on enhancing reaction kinetics for sodium-ion batteries. However, the thorough exploration of 3D architecture with a facile strategy is still challenging. Here we report that a polycrystalline Cu2-xSe film was epitaxial grown on (220) facets-exposed Cu by direct selenization of a nanoporous Cu skeleton, which is obtained by dealloying rolled CuMn@Cu alloy foil. Density functional theory calculation result shows strong adsorption energy for Se atoms on Cu (220) planes during selenization reaction, rendering a low energy consumption. By virtue of this core-shell 3D nanoporous architecture to offer abundant active sites and endow fast electron/ion transportation, the nanoporous Cu2-xSe@Cu-0.15 composite electrode exhibits remarkable sodium-ion storage properties with high reversible capacity of 950.6 µAh/cm2 at 50 µA/cm2, suprior rate capability of 457.6 µAh/cm2 at 500 µA/cm2, as well as an ultra-long stability at a high current density. Mechanism investigation reveals that the electrochemical reaction is a typical conversion-type reaction with different intermediates. This novel electrode synthetic strategy provides useful instructions to design the high-performance anode material for sodium-ion batteries.

The synthesis of Ni-Co-Fe-Se@NiCo-LDH nanoarrays on Ni foam as efficient overall water splitting electrocatalyst

The development of efficient, stable and low-cost electrocatalysts for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is the key to promote the industrialization of electrocatalytic water splitting. In this paper, the [email protected] precursor was first synthesized and then the target catalyst named [email protected] was finally synthesized by a selenization reaction based on this precursor. In a three-electrode system with 1.0 M KOH alkaline atmosphere, [email protected] requires an overpotential of 286 mV to deliver a current density of 100 mA/cm2 for OER and 113 mV at a current density of 10 mA/cm2 for HER. In addition, the material shows excellent overall water splitting performance and a low cell voltage of 1.55 V at 10 mA/cm2 is expected. By comparing the test results of [email protected] and NiCo-LDH, we found that increasing the number of metal species only slightly reduces the electron transfer impedance and does not help to increase the electrochemical surface area of the material. Density functional theory calculation shows that the presence of the Co-NiSe2 material accelerates the kinetics of hydrogen production and the Fe7Se8 material enhances the conductivity of the material. Their synergistic effect makes the [email protected] catalyst exhibit enhanced hydrogen production activity.

Oxygen Vacancy-Rich S-Scheme CeO2@Ni1–xCoxSe2 Hollow Spheres Derived from NiCo-MOF for Remarkable Photocatalytic CO2 Conversion

Photocatalytic CO2 conversion into chemicals has been a promising strategy to utilize sustainable solar energy and alleviate the greenhouse effect. Nonetheless, the achievements of these photocatalytic reactions are challenging. Herein, we present a strategy for the synthesis of hierarchical CeO2@Ni1–xCoxSe2 hollow spheres (HSs) including the successive steps of coating of the CeO2 nanolayer on SiO2 spheres, in situ growth of NiCo-MOF nanosheets, selenization reaction, and subsequent etching treatment. The hierarchical CeO2@Ni1–xCoxSe2 HSs exhibiting intimate interface contact between two nanoshells form an S-scheme heterojunction with fast charge/mass transport and excellent visible-light absorption, while maintaining the strong reducing power of electrons in the conduction band of Ni1–xCoxSe2 nanosheets and the strong oxidizing capacity of holes in the valence band of CeO2 HSs with oxygen vacancies. The S-scheme photogenerated charge transfer mechanism was testified by the work function and electron paramagnetic resonance measurements. These advantages make the optimized CeO2@Ni1–xCoxSe2 HS sample exhibit superior activity and high stability in photocatalytic CO2 reduction with a CO production rate of 25.93 μmol h–1 g–1. This work provides more opportunities to fabricate other hierarchical S-scheme semiconductor-based photocatalysts.