Conjugated Acetylenic Polymers Grafted Cuprous Oxide as an Efficient Z-Scheme Heterojunction for Photoelectrochemical Water Reduction

As attractive materials for photoeletrochemical hydrogen evolution reaction (PEC HER), conjugated polymers (e.g., conjugated acetylenic polymers [CAPs]) still show poor PEC HER performance due to the associated serious recombination of photogenerated electrons and holes. Herein, taking advantage of the in situ conversion of nanocopper into Cu₂O on copper cellulose paper during catalyzing of the Glaser coupling reaction, a general strategy for the construction of a CAPs/Cu₂O Z-scheme heterojunction for PEC water reduction is demonstrated. The as-fabricated poly(2,5-diethynylthieno[3,2-b]thiophene) (pDET)/Cu₂O Z-scheme heterojunction exhibits a carrier separation efficiency of 16.1% at 0.3 V versus reversible hydrogen electrode (RHE), which is 6.7 and 1.4-times higher respectively than those for pDET and Cu₂O under AM 1.5G irradiation (100 mW cm⁻²) in the 0.1 m Na₂SO₄ aqueous solution. Consequently, the photocurrent of the pDET/Cu₂O Z-scheme heterojunction reaches ≈ 520 µ A cm⁻² at 0.3 V versus RHE, which is much higher than pDET ( ≈ 80 µ A cm⁻²), Cu₂O ( ≈ 100 µ A cm⁻²), and the state-of-the-art cocatalyst-free organic or organic-semiconductor-based heterojunctions/homojunctions photocathodes (1–370 µ A cm⁻²). This work advances the design of polymer-based Z-scheme heterojunctions and high-performance organic photoelectrodes.     

Fabrication of Bi2WO6/In2O3 photocatalysts with efficient photocatalytic performance for the degradation of organic pollutants: Insight into the role of oxygen vacancy and heterojunction

Photocatalysis is an attractive and green strategy for organic pollutant removal. The development of alternative and effective photocatalysts has attracted great attention. Herein, we rationally engineer an alternative rich-oxygen vacancies (OVs) Bi₂WO₆/In₂O₃ composite photocatalyst via integrating the calcination and hydrothermal method for removing organic dyes (rhodamine B). Thanks to the synergistic effect of OVs and heterojunction structure, the 80 wt% Bi₂WO₆/In₂O₃ (BiIn80) displays enhanced photocatalytic degradation effect. The degradation rate of BiIn80 is up to 97.3% under light irradiation within 120 min and the reaction rate constant k value (0.03221 min⁻¹) is about 15-fold and 4.17-fold as high as those of In₂O₃ (0.00203 min⁻¹) and Bi₂WO₆ (0.00772 min⁻¹), respectively. The heterostructure of Bi₂WO₆/In₂O₃ can extend the lifespan of the photogenerated charge carriers. Moreover, the density functional theory (DFT) calculations reveal that the OVs in Bi₂WO₆/In₂O₃ can boost visible light absorbability by decreasing band gap value and serve as the extra electron transfer channels to enhance the separation efficiency of photogenerated electron-hole pairs. This study not only provides an alternative route for fabricating highly efficient heterojunction photocatalysts, but also obtains better understanding of the synergistic effect of OVs and heterojunction on enhancing the photocatalytic performance.     

Ultrathin In2O3 Nanosheets toward High Responsivity and Rejection Ratio Visible-Blind UV Photodetection

Photoelectrochemical-type visible-blind ultraviolet photodetectors (PEC VBUV PDs) have gained ever-growing attention due to their simple fabrication processes, uncomplicated packaging technology, and high sensitivity. However, it is still challenging to achieve high-performance PEC VBUV PDs based on a single material with good spectral selectivity. Here, it is demonstrated that individual ultrathin indium oxide (In₂O₃) nanosheets (NSs) are suitable for designing high-performance PEC VBUV PDs with high responsivity and UV/visible rejection ratio for the first time. In₂O₃ NSs PEC PDs show excellent UV photodetection capability with an ultrahigh photoresponsivity of 172.36 mA W⁻¹ and a high specific detectivity of 4.43 × 10¹¹ Jones under 254 nm irradiation, which originates from the smaller charge transfer resistance (R_ct) at the In₂O₃ NSs/electrolyte interface. The light absorption of In₂O₃ NSs takes a blueshift due to the quantum confinement effect, granting good spectral selectivity for visible-blind detection. The UV/visible rejection ratio of In₂O₃ NSs PEC PDs is 1567, which is 30 times higher than that of In₂O₃ nanoparticles (NPs) and exceeds all recently reported PEC VBUV PDs. Moreover, In₂O₃ NSs PEC PDs show good stability and good underwater imaging capability. The results verify that ultrathin In₂O₃ NSs have potential in underwater optoelectronic devices.     

Roles of Cobalt-Coordinated Polymeric Perylene Diimide in Hematite Photoanodes for Improved Water Oxidation

Interfacial charge recombination is a permanent issue that impedes the photon energy utilization in photoelectrochemical (PEC) water splitting. Herein, a conjugated polymer, urea linked perylene diimide polymer (PDI), is introduced to the designation of hematite-based composite photoanodes. On account of its unique molecule structure with abundant electronegative atoms, the O and N atoms with lone electron pairs can bond with Fe atoms at the surface of Zr⁴⁺ doped α-Fe₂O₃ (Zr:Fe₂O₃) and thus establish charge transfer channels for expediting hole separation and migration. Meanwhile, PDI molecules can passivate the surface states in Zr:Fe₂O₃, which is in favor of suppressing carrier recombination. Particularly, Co²⁺ is used to coordinate with PDI (Co-PDI) to accelerate hole extraction as well as utilization, and the as-obtained Co-PDI form type-II heterojunction with Zr:Fe₂O₃. Such a photoanode configuration takes advantage of the unique molecule structure of PDI, and the target Co-PDI/Zr:Fe₂O₃ photoanodes eventually attain a photocurrent density of 2.17 mA cm⁻², which is inspirational for unearthing the potential use of conjugative molecules in PEC fields.     

Surface Self-Transforming FeTi-LDH Overlayer in Fe2O3/Fe2TiO5 Photoanode for Improved Water Oxidation

Integrating hematite nanostructures with efficient layer double hydroxides (LDHs) is highly desirable to improve the photoelectrochemical (PEC) water oxidation performance. Here, an innovative and facile strategy is developed to fabricate the FeTi-LDH overlayer decorated Fe₂O₃/Fe₂TiO₅ photoanode via a surface self-transformation induced by the co-treatment of hydrazine and NaOH at room temperature. Electrochemical measurements find that this favorable structure can not only facilitate the charge transfer/separation at the electrode/electrolyte interface but also accelerate the surface water oxidation kinetics. Consequently, the as-obtained Fe₂O₃/Fe₂TiO₅/LDH photoanode exhibits a remarkably increased photocurrent density of 3.54 mA cm⁻² at 1.23 V versus reversible hydrogen electrode (RHE) accompanied by an obvious cathodic shift (≈140 mV) in the onset potential. This work opens up a new and effective pathway for the design of high-performance hematite photoanodes toward efficient PEC water oxidation.     

TiO2 ALD decorated CuO/BiVO4 p-n heterojunction for improved photoelectrochemical water splitting

Bismuth vanadate (BiVO₄) is a promising photoanode material owing to the narrow bandgap, appropriate band position, and excellent resistance against photocorrosion, however, the performance of photoelectrochemical (PEC) water splitting is largely limited by the poor carrier separation and transport ability. To address these issues, for the first time, we fabricate BiVO₄ film/CuO nanocone p-n junctions as photoanodes by combing a facile spin-coating process and water bath reaction. This structure strengthens the light harvesting and promotes the charge separation and transport ability. The surface defects states are passivated by coating conformally ultrathin TiO₂ onto CuO surface through atomic layer deposition (ALD) technique. Benefiting from the favorable morphology, energy band, and surface treatment, the BiVO₄/CuO/TiO₂ heterojunction generates an improved photocurrent that is much higher than pure BiVO₄. The detailed mechanism investigations indicate that the synergetic optimization of charge separation and injection efficiency in the bulk and surface of photoelectrodes can significantly improve the performance of PEC cells.     

In Situ Constructed Perovskite–Chalcogenide Heterojunction for Photocatalytic CO2 Reduction

Perovskite nanocrystals (PNCs) are promising candidates for solar-to-fuel conversions yet exhibit low photocatalytic activities mainly due to serious recombination of photogenerated charge carriers. Constructing heterojunction is regarded as an effective method to promote the separation of charge carriers in PNCs. However, the low interfacial quality and non-directional charge transfer in heterojunction lead to low charge transfer efficiency. Herein, a CsPbBr₃–CdZnS heterojunction is designed and prepared via an in situ hot-injection method for photocatalytic CO₂ reduction. It is found that the high-quality interface in heterojunction and anisotropic charge transfer of CdZnS nanorods (NRs) enable efficient spatial separation of charge carriers in CsPbBr₃–CdZnS heterojunction. The CsPbBr₃–CdZnS heterojunction achieves a higher CO yield (55.8 µmol g⁻¹ h⁻¹) than that of the pristine CsPbBr₃ NCs (13.9 µmol g⁻¹ h⁻¹). Furthermore, spectroscopic experiments and density functional theory (DFT) simulations further confirm that the suppressed recombination of charge carriers and lowered energy barrier for CO₂ reduction contribute to the improved photocatalytic activity of the CsPbBr₃–CdZnS heterojunction. This work demonstrates a valid method to construct high-quality heterojunction with directional charge transfer for photocatalytic CO₂ reduction. This study is expected to pave a new avenue to design perovskite–chalcogenide heterojunction.     

2D Cobalt Chalcogenide Heteronanostructures Enable Efficient Alkaline Hydrogen Evolution Reaction

The development of high-efficiency non-precious metal electrocatalysts for alkaline electrolyte hydrogen evolution reactions (HER) is of great significance in energy conversion to overcome the limited supply of fossil fuels and carbon emission. Here, a highly active electrocatalyst is presented for hydrogen production, consisting of 2D CoSe₂/Co₃S₄ heterostructured nanosheets along Co₃O₄ nanofibers. The different reaction rate between the ion exchange reaction and redox reaction leads to the heterogeneous volume swelling, promoting the growth of 2D structure. The 2D/1D heteronanostructures enable the improved the electrochemical active area, the number of active sites, and more favorable H binding energy compared to individual cobalt chalcogenides. The roles of the different composition of the heterojunction are investigated, and the electrocatalysts based on the CoSe₂/Co₃S₄@Co₃O₄ exhibited an overpotential as low as 165 mV for 10 mA cm⁻² and 393 mV for 200 mA cm⁻² in 1 m KOH electrolyte. The as-prepared electrocatalysts remained active after 55 h operation without any significant decrease, indicating the excellent long-term operation stability of the electrode. The Faradaic efficiency of hydrogen production is close to 100% at different voltages. This work provides a new design strategy toward Co-based catalysts for efficient alkaline HER.     

Z-Scheme Modulated Charge Transfer on InVO4@ZnIn2S4 for Durable Overall Water Splitting

The charge transfer within heterojunction is crucial for the efficiency and stability of photocatalyst for overall water splitting (OWS). Herein, InVO₄ nanosheets have been employed as a support for the lateral epitaxial growth of ZnIn₂S₄ nanosheets to produce hierarchical InVO₄@ZnIn₂S₄ (InVZ) heterojunctions. The distinct branching heterostructure facilitates active site exposure and mass transfer, further boosting the participation of ZnIn₂S₄ and InVO₄ for proton reduction and water oxidation, respectively. The unique Z-scheme modulated charge transfer, visualized by simulation and in situ analysis, has been proved to promote the spatial separation of photoexcited charges and strengthen the anti-photocorrosion capability of InVZ. The optimized InVZ heterojunction presents improved OWS (153.3 µmol h⁻¹ g⁻¹ for H₂ and 76.9 µmol h⁻¹ g⁻¹ for O₂) and competitive H₂ production (21090 µmol h⁻¹ g⁻¹). Even after 20 times (100 h) of cycle experiment, it still holds more than 88% OWS activity and a complete structure.     

Construction of Bimetallic Heterojunction Based on Porous Engineering for High Performance Flexible Asymmetric Supercapacitors

It remains a great challenge to design and manufacture battery-type supercapacitors with satisfactory flexibility, appropriate mechanical property, and high energy density under high power density. Herein, a concept of porous engineering is proposed to simply prepare two-layered bimetallic heterojunction with porous structures. This concept is successfully applied in fabrication of flexible electrode based on CuO-Co(OH)₂ lamella on Cu-plated carbon cloth (named as CPCC@CuO@Co(OH)₂). The unique structure brings the electrode a high specific capacity of 3620 mF cm⁻² at 2 mA cm⁻² and appropriate mechanical properties with Young's modulus of 302.0 MPa. Density functional theory calculations show that porous heterojunction provides a higher intensity of electron state density near the Fermi level (E–E_f = 0 eV), leading to a highly conductive CPCC@CuO@Co(OH)₂ electrode with both efficient charge transport and rapid ion diffusion. Notably, the supercapacitor assembled from CPCC@CuO@Co(OH)₂//CC@AC shows high energy density of 127.7 W h kg⁻¹ at 750.0 W kg⁻¹, remarkable cycling performance (95.53% capacity maintaining after 10 000 cycles), and desired mechanical flexibility. The methodology and results in this work will accelerate the transformative developments of flexible energy storage devices in practical applications.     

Hybrid MOF Template-Directed Construction of Hollow-Structured In2O3@ZrO2 Heterostructure for Enhancing Hydrogenation of CO2 to Methanol

Direct hydrogenation of CO₂ to methanol using green hydrogen has emerged as a promising method for carbon neutrality, but qualifying catalysts represent a grand challenge. In₂O₃/ZrO₂ catalyst has been extensively applied in methanol synthesis due to its superior activity; however, the electronic effect by strong oxides-support interactions between In₂O₃ and ZrO₂ at the In₂O₃/ZrO₂ interface is poorly understood. In this work, abundant In₂O₃/ZrO₂ heterointerfaces are engineered in a hollow-structured In₂O₃@ZrO₂ heterostructure through a facile pyrolysis of a hybrid metal–organic framework precursor MIL-68@UiO-66. Owing to well-defined In₂O₃/ZrO₂ heterointerfaces, the resultant In₂O₃@ZrO₂ exhibits superior activity and stability toward CO₂ hydrogenation to methanol, which can afford a high methanol selectivity of 84.6% at a conversion of 10.4% at 290 °C, and 3.0 MPa with a methanol space-time yield of up to 0.29 g_MeOH g_cat⁻¹ h⁻¹. Extensive characterization demonstrates that there is a strong correlation between the strong electronic In₂O₃–ZrO₂ interaction and catalytic selectivity. At In₂O₃/ZrO₂ heterointerfaces, the electron tends to transfer from ZrO₂ to In₂O₃ surface, which facilitates H₂ dissociation and the hydrogenation of formate (HCOO*) and methoxy (CH₃O*) species to methanol. This study provides an insight into the In₂O₃-based catalysts and offers appealing opportunities for developing heterostructured CO₂ hydrogenation catalysts with excellent activity.     

Engineering Interfacial Built-in Electric Field in Polymetallic Phosphide Heterostructures for Superior Supercapacitors and Electrocatalytic Hydrogen Evolution

Herein, a patterned rod-like CoP@NiCoP core-shell heterostructure is designed to consist of CoP nanowires cross-linked with NiCoP nanosheets in tight strings. The interfacial interaction within the heterojunction between the two components generates a built-in electric field that adjusts the interfacial charge state and create more active sites, accelerating the charge transfer and improving supercapacitor and electrocatalytic performance. The unique core-shell structure suppresses the volume expansion during charging and discharging, achieving excellent stability. As a result, CoP@NiCoP exhibits a high specific capacitance of 2.9 F cm⁻² at a current density of 3 mA cm⁻² and a high ion diffusion rate (D_ion is 2.95 × 10⁻¹⁴ cm² s⁻¹) during charging/discharging. The assembled asymmetric supercapacitor CoP@NiCoP//AC exhibits a high energy density of 42.2 Wh kg⁻¹ at a power density of 126.5 W kg⁻¹ and excellent stability with a capacitance retention rate of 83.8% after 10 000 cycles. Furthermore, the modulated effect induced by the interfacial interaction also endows the self-supported electrode with excellent electrocatalytic HER performance with an overpotential of 71 mV at 10 mA cm⁻². This research may provide a new perspective on the generation of built-in electric field through the rational design of heterogeneous structures for improving the electrochemical and electrocatalytical performance.     

Urchin-Like Structured MoO2/Mo3P/Mo2C Triple-Interface Heterojunction Encapsulated within Nitrogen-Doped Carbon for Enhanced Hydrogen Evolution Reaction

The development of highly efficient and cost-effective hydrogen evolution reaction (HER) catalysts is highly desirable to efficiently promote the HER process, especially under alkaline condition. Herein, a polyoxometalates-organic-complex-induced carbonization method is developed to construct MoO₂/Mo₃P/Mo₂C triple-interface heterojunction encapsulated into nitrogen-doped carbon with urchin-like structure using ammonium phosphomolybdate and dopamine. Furthermore, the mass ratio of dopamine and ammonium phosphomolybdate is found critical for the successful formation of such triple-interface heterojunction. Theoretical calculation results demonstrate that such triple-interface heterojunctions possess thermodynamically favorable water dissociation Gibbs free energy (ΔG_H2O) of -1.28 eV and hydrogen adsorption Gibbs free energy (ΔG_H*) of -0.41 eV due to the synergistic effect of Mo₂C and Mo₃P as water dissociation site and H* adsorption/desorption sites during the HER process in comparison to the corresponding single components. Notably, the optimal heterostructures exhibit the highest HER activity with the low overpotential of 69 mV at the current density of 10 mA cm⁻² and a small Tafel slope of 60.4 mV dec⁻¹ as well as good long-term stability for 125 h. Such remarkable results have been theoretically and experimentally proven to be due to the synergistic effect between the unique heterostructures and the encapsulated nitrogen-doped carbon.     

Ultrahigh Detectivity Broad Spectrum UV Photodetector with Rapid Response Speed Based on p-β Ga2O3/n-GaN Heterojunction Fabricated by a Reversed Substitution Doping Method

An excellent broad-spectrum (220–380 nm) UV photodetector, covering the UVA-UVC wavelength range, with an ultrahigh detectivity of ≈10¹⁵ cm Hz^1/2 W⁻¹, is reported. It is based on a p-β Ga₂O₃/n-GaN heterojunction, in which p-β Ga₂O₃ is synthesized by thermal oxidation of GaN and a heterostructure is constructed with the bottom n-GaN. XRD shows the oxide layer is (−201) preferred oriented β-phase Ga₂O₃ films. SIMS and XPS indicate that the residual N atoms as dopants remain in β Ga₂O₃. XPS also demonstrates that the Fermi level is 0.2 eV lower than the central level of the band gap, indicating that the dominant carriers are holes and the β Ga₂O₃ is p-type conductive. Under a bias of −5 V, the photoresponsivity is 56 and 22 A W⁻¹ for 255 and 360 nm, respectively. Correspondingly, the detectivities reach an ultrahigh value of 2.7 × 10¹⁵ cm Hz^1/2 W⁻¹ (255 nm) and 1.1 × 10¹⁵ cm Hz^1/2 W⁻¹ (360 nm). The high performance of this UV photodetector is attributed mainly to the continuous conduction band of the p-β Ga₂O₃/n-GaN heterojunction without a potential energy barrier, which is more helpful for photogenerated electron transport from the space charge region to the n-type GaN layer.     

Hierarchical CdS Nanorod@SnO2 Nanobowl Arrays for Efficient and Stable Photoelectrochemical Hydrogen Generation

An efficient photoanode based on CdS nanorod@SnO₂ nanobowl (CdS NR@SnO₂ NB) arrays is designed and fabricated by the preparation of SnO₂ nanobowl arrays via nanosphere lithography followed by hydrothermal growth of CdS nanorods on the inner surface of the SnO₂ nanobowls. A photoelectrochemical (PEC) device constructed by using this hierarchical CdS NR@SnO₂ NB photoanode presents significantly enhanced performance with a photocurrent density of 3.8 mA cm^?2 at 1.23 V versus a reversible hydrogen electrode (RHE) under AM1.5G solar light irradiation, which is about 2.5 times higher than that of CdS nanorod arrays. After coating with a thin layer of SiO₂, the photostability of the CdS NR@SnO₂ NB arrays is greatly enhanced, resulting in a stable photoanode with a photocurrent density of 3.0 mA cm^?2 retained at 1.23 V versus the RHE. The much improved performance of the CdS NR@SnO₂ NB arrays toward PEC hydrogen generation can be ascribed to enlarged surface area arising from the hierarchical nanostructures, improved light harvesting owing to the NR@NB architecture containing multiple scattering centers, and enhanced charge separation/collection efficiency due to the favorable CdS–SnO₂ heterojunction.     

Synergy of Ultrathin CoOx Overlayer and Nickel Single Atoms on Hematite Nanorods for Efficient Photo-Electrochemical Water Splitting

To solve surface carrier recombination and sluggish water oxidation kinetics of hematite (α-Fe₂O₃) photoanodes, herein, an attractive surface modification strategy is developed to successively deposit ultrathin CoO_x overlayer and Ni single atoms on titanium (Ti)-doped α-Fe₂O₃ (Ti:Fe₂O₃) nanorods through a two-step atomic layer deposition (ALD) and photodeposition process. The collaborative decoration of ultrathin CoO_x overlayer and Ni single atoms can trigger a big boost in photo-electrochemical (PEC) performance for water splitting over the obtained Ti:Fe₂O₃/CoO_x/Ni photoanode, with the photocurrent density reaching 1.05 mA cm⁻² at 1.23 V vs. reversible hydrogen electrode (RHE), more than three times that of Ti:Fe₂O₃ (0.326 mA cm⁻²). Electrochemical and electronic investigations reveal that the surface passivation effect of ultrathin CoO_x overlayer can reduce surface carrier recombination, while the catalysis effect of Ni single atoms can accelerate water oxidation kinetics. Moreover, theoretical calculations evidence that the synergy of ultrathin CoO_x overlayer and Ni single atoms can lower the adsorption free energy of OH* intermediates and relieve the potential-determining step (PDS) for oxygen evolution reaction (OER). This work provides an exemplary modification through rational engineering of surface electrochemical and electronic properties for the improved PEC performances, which can be applied in other metal oxide semiconductors as well.     

Spatial Specific Janus S-Scheme Photocatalyst with Enhanced H2O2 Production Performance

Photocatalytic oxygen reduction reaction (ORR) for H₂O₂ production in the absence of sacrificing agents is a green approach and of great significance, where the design of photocatalysts with high performance is the central task. Herein, a spatial specific S-scheme heterojunction design by introducing a novel semiconducting pair with a S-scheme mechanism in a purpose-designed Janus core–shell-structured hollow morphology is reported. In this design, TiO₂ nanocrystals are grown inside the inner wall of resorcinol-formaldehyde (RF) resin hollow nanocakes with a reverse bumpy ball morphology (TiO₂@RF). The S-scheme heterojunction preserves the high redox ability of the TiO₂ and RF pair, the spatial specific Janus design enhances the charge separation, promotes active site exposure, and reduces the H₂O₂ decomposition to a large extent. The TiO₂@RF photocatalyst shows a high H₂O₂ yield of 66.6 mM g⁻¹ h⁻¹ and solar-to-chemical conversion efficiency of 1.11%, superior to another Janus structure (RF@TiO₂) with the same heterojunction but a reversed Janus spatial arrangement, and most reported photocatalysts under similar reaction conditions. The work has paved the way toward the design of next-generation photocatalysts for green synthesis of H₂O₂ production.     

Dye degradation over the multivalent charge- and solid solution-type n-MoS2/p-WO3 based diode catalyst under dark condition with a self-supporting charge carrier transfer mechanism

Pollution of water by synthetic dyes is of great concern because of the large production and usage of dyestuffs throughout the world. For dye elimination purpose, the p-n heterojunction Sb-doped MW-x composite catalysts prepared with different Mo:W precursor molar contents were synthesized via one-pot hydrothermal method. The selection in metal precursors is intended to design a composite catalyst with multiple valency in each phase. The structural, morphological, electrochemical property, and optical band gap of the composite catalyst were studied. The catalytic performance of Sb-MW composite catalysts was studied for the degradation of MB without light irradiation. It was observed that Sb-MW-4 showed superior catalytic performance to completely degrade 20 ppm MB dye solution with 20 mg catalyst in 14 min under dark condition. The composite catalyst was composed of n-(Mo,W)(O,S)₂ oxysulfide in a disordered MoS₂ framework and p-(W,Mo)(S,O)₃ sulfo-oxide in a WO₃ structure or was abbreviatedly named as n-MoS₂/p-WO₃ based catalyst. The degradation reaction for MB dye had an apparent rate constant of 3.5 × 10⁻¹ min⁻¹. This catalyst also showed excellent stability and reusability for degrading MB dye pollutant. The degradation mechanism under dark condition is proposed.     

Ultralight Flexible Electrodes of Nitrogen-Doped Carbon Macrotube Sponges for High-Performance Supercapacitors

Light-weight and flexible supercapacitors with outstanding electrochemical performances are strongly desired in portable and wearable electronics. Here, ultralight nitrogen-doped carbon macrotube (N-CMT) sponges with 3D interconnected macroporous structures are fabricated and used as substrate to grow nickel ferrite (NiFe₂O₄) nanoparticles by vapor diffusion–precipitation and in situ growth. This process effectively suppresses the agglomeration of NiFe₂O₄, enabling good interfacial contact between N-CMT sponges and NiFe₂O₄. More remarkably, the as-synthesized NiFe₂O₄/N-CMT composite sponges can be directly used as electrodes without additional processing that could cause agglomeration and reduction of active sites. Benefiting from the tubular structure and the synergetic effect of NiFe₂O₄ and N-CMT, the NiFe₂O₄/N-CMT-2 exhibits a high specific capacitance of 715.4 F g⁻¹ at a current density of 1 A g⁻¹, and 508.3 F g⁻¹ at 10 A g⁻¹, with 90.9% of capacitance retention after 50 000 cycles at 1 A g⁻¹ in an alkaline electrolyte. Furthermore, flexible supercapacitors are fabricated, yielding areal specific capacitances of 1397.4 and 1041.2 mF cm⁻² at 0.5 and 8 mA cm⁻², respectively. They also exhibit exceptional cycling performance with capacitance retention of 92.9% at 1 mA cm⁻² after 10 000 cycles under bending. This work paves a new way to develop flexible, light-weight, and high-performance energy storage devices.     

Accelerating Industrial-Level NO3− Electroreduction to Ammonia on Cu Grain Boundary Sites via Heteroatom Doping Strategy

Although the electrocatalytic nitrate reduction reaction (NO₃⁻RR) is an attractive NH₃ synthesis route, it suffers from low yield due to the lack of efficient catalysts. Here, this work reports a novel grain boundary (GB)-rich Sn-Cu catalyst, derived from in situ electroreduction of Sn-doped CuO nanoflower, for effectively electrochemical converting NO₃⁻ to NH₃. The optimized Sn_1%-Cu electrode achieves a high NH₃ yield rate of 1.98 mmol h⁻¹ cm⁻² with an industrial-level current density of −425 mA cm⁻² at −0.55 V versus a reversible hydrogen electrode (RHE) and a maximum Faradaic efficiency of 98.2% at −0.51 V versus RHE, outperforming the pure Cu electrode. In situ Raman and attenuated total reflection Fourier transform infrared spectroscopies reveal the reaction pathway of NO₃⁻RR to NH₃ by monitoring the adsorption property of reaction intermediates. Density functional theory calculations clarify that the high-density GB active sites and the competitive hydrogen evolution reaction (HER) suppression induced by Sn doping synergistically promote highly active and selective NH₃ synthesis from NO₃⁻RR. This work paves an avenue for efficient NH₃ synthesis over Cu catalyst by in situ reconstruction of GB sites with heteroatom doping.