Synthesis of Large Surface‐Area g‐C3N4 Comodified with MnOx and Au‐TiO2 as Efficient Visible‐Light Photocatalysts for Fuel Production

Herein, this study successfully fabricates porous g‐C₃N₄‐based nanocomposites by decorating sheet‐like nanostructured MnO_x and subsequently coupling Au‐modified nanocrystalline TiO₂. It is clearly demonstrated that the as‐prepared amount‐optimized nanocomposite exhibits exceptional visible‐light photocatalytic activities for CO₂ conversion to CH₄ and for H₂ evolution, respectively by ≈28‐time (140 µmol g^?1 h^?1) and ≈31‐time (313 µmol g^?1 h^?1) enhancement compared to the widely accepted outstanding g‐C₃N₄ prepared with urea as the raw material, along with the calculated quantum efficiencies of ≈4.92% and 2.78% at 420 nm wavelength. It is confirmed mainly based on the steady‐state surface photovoltage spectra, transient‐state surface photovoltage responses, fluorescence spectra related to the produced ?OH amount, and electrochemical reduction curves that the exceptional photoactivities are comprehensively attributed to the large surface area (85.5 m² g^?1) due to the porous structure, to the greatly enhanced charge separation and to the introduced catalytic functions to the carrier‐related redox reactions by decorating MnO_x and coupling Au‐TiO₂, respectively, to modulate holes and electrons. Moreover, it is suggested mainly based on the photocatalytic experiments of CO₂ reduction with isotope ¹³CO₂ and D₂O that the produced ?CO₂ and ?H as active radicals would be dominant to initiate the conversion of CO₂ to CH₄.     

Exceptional Visible‐Light‐Driven Cocatalyst‐Free Photocatalytic Activity of g‐C3N4 by Well Designed Nanocomposites with Plasmonic Au and SnO2

In this work, plasmonic Au/SnO₂/g‐C₃N₄ (Au/SO/CN) nanocomposites have been successfully synthesized and applied in the H₂ evolution as photocatalysts, which exhibit superior photocatalytic activities and favorable stability without any cocatalyst under visible‐light irradiation. The amount‐optimized 2Au/6SO/CN nanocomposite capable of producing approximately 770 μmol g^?1 h^?1 H₂ gas under λ > 400 nm light illumination far surpasses the H₂ gas output of SO/CN (130 μmol g^?1), Au/CN (112 μmol g^?1 h^?1), and CN (11 μmol g^?1 h^?1) as a contrast. In addition, the photocatalytic activity of 2Au/6SO/CN maintains unchanged for 5 runs in 5 h. The enhanced photoactivity for H₂ evolution is attributed to the prominently promoted photogenerated charge separation via the excited electron transfer from plasmonic Au (≈520 nm) and CN (470 nm > λ > 400 nm) to SO, as indicated by the surface photovoltage spectra, photoelectrochemical I–V curves, electrochemical impedance spectra, examination of formed hydroxyl radicals, and photocurrent action spectra. Moreover, the Kelvin probe test indicates that the newly aligned conduction band of SO in the fabricated 2Au/6SO/CN is indispensable to assist developing a proper energy platform for the photocatalytic H₂ evolution. This work distinctly provides a feasible strategy to synthesize highly efficient plasmonic‐assisted CN‐based photocatalysts utilized for solar fuel production.     

Novel Black BiVO4/TiO2−x Photoanode with Enhanced Photon Absorption and Charge Separation for Efficient and Stable Solar Water Splitting

Recent advances in solar water splitting by using BiVO₄ as a photoanode have greatly optimized charge carrier and reaction dynamics, but relatively wide bandgap and poor photostability are still bottlenecks. Here, an excellent photoanode of black BiVO₄@amorphous TiO_2?x to tackle both problems is reported. Its applied bias photon‐to‐current efficiency for solar water splitting is up to 2.5%, which is a new record for a single oxide photon absorber. This unique core–shell structure is fabricated by coating amorphous TiO₂ on nanoporous BiVO₄ with the aid of atomic layer deposition and further hydrogen plasma treatment at room temperature. The black BiVO₄ with moderate oxygen vacancies reveals a bandgap reduction of ≈0.3 eV and significantly enhances solar utilization, charge transport and separation simultaneously, compared with conventional BiVO₄. The amorphous layer of TiO_2?x acts as both oxygen‐evolution catalyst and protection layer, which suppresses anodic photocorrosion to stabilize black BiVO₄. This configuration of black BiVO₄@amorphous TiO_2?x may provide an effective strategy to prompt solar water splitting toward practical applications.     

g‐C3N4‐Based Heterostructured Photocatalysts

Photocatalysis is considered as one of the promising routes to solve the energy and environmental crises by utilizing solar energy. Graphitic carbon nitride (g‐C₃N₄) has attracted worldwide attention due to its visible‐light activity, facile synthesis from low‐cost materials, chemical stability, and unique layered structure. However, the pure g‐C₃N₄ photocatalyst still suffers from its low separation efficiency of photogenerated charge carriers, which results in unsatisfactory photocatalytic activity. Recently, g‐C₃N₄‐based heterostructures have become research hotspots for their greatly enhanced charge carrier separation efficiency and photocatalytic performance. According to the different transfer mechanisms of photogenerated charge carriers between g‐C₃N₄ and the coupled components, the g‐C₃N₄‐based heterostructured photocatalysts can be divided into the following categories: g‐C₃N₄‐based conventional type II heterojunction, g‐C₃N₄‐based Z‐scheme heterojunction, g‐C₃N₄‐based p–n heterojunction, g‐C₃N₄/metal heterostructure, and g‐C₃N₄/carbon heterostructure. This review summarizes the recent significant progress on the design of g‐C₃N₄‐based heterostructured photocatalysts and their special separation/transfer mechanisms of photogenerated charge carriers. Moreover, their applications in environmental and energy fields, e.g., water splitting, carbon dioxide reduction, and degradation of pollutants, are also reviewed. Finally, some concluding remarks and perspectives on the challenges and opportunities for exploring advanced g‐C₃N₄‐based heterostructured photocatalysts are presented.     

New Insights into Defect‐Mediated Heterostructures for Photoelectrochemical Water Splitting

Understanding the interfacial electronic structures of heterojunctions, a challenging undertaking, is extremely important to the design of photoelectrodes for efficient water splitting. The heterostructured interfaces in terms of crystal defects at the atomic‐level exemplified by TiO₂/BiVO₄ are studied. Results from both experimental observations and theoretical calculations clearly confirm the spontaneous formation of defective interfaces in the heterostructures. TiO₂/BiVO₄ junction with engineered interfacial defects can efficiently increase the carrier density and extend the lifetime of electrons. The inherent phenomenon of defective electronic structures in different heterostructures creates a significant impact on their photoelectrochemical performance. The synergetic effect between defect‐mediated mechanism and organic quantum dots sensitization yields significantly increased photoconversion efficiency, which is even superior to that of common metal sulfide sensitized ones. This result demonstrates an approach worthy for the design and fabrication of defect‐mediated heterostructures for water splitting, without utilizing harmful metal sulfides. Moreover, new insights into the influence of intrinsic defects on the interfacial charge transfer process between two different semiconductors for energy‐related applications have also been provided.     

Au/TiO2–gC3N4 Nanocomposites for Enhanced Photocatalytic H2 Production from Water under Visible Light Irradiation with Very Low Quantities of Sacrificial Agents

Here for the first time the design and optimization are presented of a three‐component Au/TiO₂–gC₃N₄ nanocomposite photocatalyst able to efficiently produce H₂ from water using very low amounts of sacrificial agents and under visible light irradiation. This enhanced photocatalytic behavior compared to Au/TiO₂ and Au/gC₃N₄ materials is the result of synergetic effects due to high quality assembly and interface between the three components. This optimized nanoscale assembly characterized by simultaneous favorable nanoheterojunction formation between g‐C₃N₄ and TiO₂ semiconductors, as well as AuNPs/gC₃N₄ and AuNPs/TiO₂ junctions, leads to enhanced visible light harvesting, charge separation, and H₂ production. This composite photocatalyst yields a high H₂ production (350 µmol^?1 h^?1 g_catalyst^?1) under visible light irradiation with minimal amounts of sacrificial agent (≤1 vol%), corresponding to activities much higher than reported so far under comparable conditions.     

1D Co‐Pi Modified BiVO4/ZnO Junction Cascade for Efficient Photoelectrochemical Water Cleavage

The most important factors dominating solar hydrogen synthesis efficiency include light absorption, charge separation and transport, and surface chemical reactions (charge utilization). In order to tackle these factors, an ordered 1D junction cascade photoelectrode for water splitting, grown via a simple low‐cost solution‐based process and consisting of nanoparticulate BiVO₄ on 1D ZnO rods with cobalt phosphate (Co‐Pi) on the surface is synthesized. Flat‐band measurements reveal the feasibility of charge transfer from BiVO₄ to ZnO, supported by PL measurements and photocurrent observation in the presence of an efficient hole scavenger, which demonstrate that quenching of luminescence of BiVO₄ and enhanced current are caused by electron transfer from BiVO₄ to ZnO. A dramatic cathodic shift in onset potential under both visible and full arc irradiation, coupled with a 12‐fold increase in photocurrent (ca. 3 mA cm^‐2) are observed compared to BiVO₄, resulting in ≈47% IPCE at 410 nm (4% for BiVO₄) with high solar energy conversion efficiency (0.88%). The reasons for these enhancements stem from enhanced light absorption and trapping, in situ rectifying electron transfer from BiVO₄ to ZnO, hole transfer to Co‐Pi for water oxidation, and facilitating electron transport along 1D ZnO.     

A Facile Method to Improve the Photocatalytic and Lithium‐Ion Rechargeable Battery Performance of TiO2 Nanocrystals

TiO₂ has been well studied as an ultraviolet (UV) photocatalyst and electrode material for lithium‐ion rechargeable batteries. Recent studies have shown that hydrogenated TiO₂ displayed better photocatalytic and lithium ion battery performances. Here it is demonstrated that the photocatalytic and battery performances of TiO₂ nanocrystals can be successfully improved with a facile low‐temperature vacuum process. These TiO₂ nanocrystals extend their optical absorption far into the visible‐light region, display nanometer‐scale surface atomic rearrangement, possess superoxide ion characteristics at room temperature without light irradiation, show a 4‐fold improvement in photocatalytic activity, and has 30% better performance in capacity and charge/discharge rates for lithium ion battery. This facile method could provide an alternative and effective approach to improve the performance of TiO₂ and other materials towards their practical applications.     

Retarded Charge–Carrier Recombination in Photoelectrochemical Cells from Plasmon‐Induced Resonance Energy Transfer

N‐type metal oxides such as hematite (α‐Fe₂O₃) and bismuth vanadate (BiVO₄) are promising candidate materials for efficient photoelectrochemical water splitting; however, their short minority carrier diffusion length and restricted carrier lifetime result in undesired rapid charge recombination. Herein, a 2D arranged globular Au nanosphere (NS) monolayer array with a highly ordered hexagonal hole pattern (hereafter, Au array) is introduced onto the surface of photoanodes comprised of metal oxide films via a facile drying and transfer‐printing process. Through plasmon‐induced resonance energy transfer, the Au array provides a strong electromagnetic field in the near‐surface area of the metal oxide film. The near‐field coupling interaction and amplification of the electromagnetic field suppress the charge recombination with long‐lived photogenerated holes and simultaneously enhance the light harvesting and charge transfer efficiencies. Consequently, an over 3.3‐fold higher photocurrent density at 1.23 V versus reversible hydrogen electrode (RHE) is achieved for the Au array/α‐Fe₂O₃. Furthermore, the high versatility of this transfer printing of Au arrays is demonstrated by introducing it on the molybdenum‐doped BiVO₄ film, resulting in 1.5‐fold higher photocurrent density at 1.23 V versus RHE. The tailored metal film design can provide a potential strategy for the versatile application in various light‐mediated energy conversion and optoelectronic devices.     

Iridium Oxide‐Assisted Plasmon‐Induced Hot Carriers: Improvement on Kinetics and Thermodynamics of Hot Carriers

Plasmonic nanostructures are capable of driving photocatalysis through absorbing photons in the visible region of the solar spectrum. Unfortunately, the short lifetime of plasmon‐induced hot carriers and sluggish surface chemical reactions significantly limit their photocatalytic efficiencies. Moreover, the thermodynamically favored excitation mechanism of plasmonic photocatalytic reactions is unclear. The mechanism of how the plasmonic catalyst could enhance the performance of chemical reaction and the limitation of localized surface plasmon resonance devices is proposed. In addition, a design is demonstrated through co‐catalyst decorated plasmonic nanoparticles Au/IrO_X upon a semiconductor nanowire‐array TiO₂ electrode that are able to considerably improve the lifetime of plasmon‐induced charge‐carriers and further facilitate the kinetics of chemical reaction. A thermodynamically favored excitation with improved kinetics of hot carriers is revealed through electrochemical studies and characterization of X‐ray absorption spectrum. This discovery provides an opportunity to efficiently manage hot carriers that are generated from metal nanostructures through surface plasmon effects for photocatalysis applications.     

TiO2 Nanocrystals Synthesized by Laser Pyrolysis for the Up‐Scaling of Efficient Solid‐State Dye‐Sensitized Solar Cells

A crucial issue regarding emerging nanotechnologies remains the up‐scaling of new functional nanostructured materials towards their implementation in high performance applications on a large scale. In this context, we demonstrate high efficiency solid‐state dye‐sensitized solar cells prepared from new porous TiO₂ photoanodes based on laser pyrolysis nanocrystals. This strategy exploits a reduced number of processing steps as well as non‐toxic chemical compounds to demonstrate highly porous TiO₂ films. The possibility to easily tune the TiO₂ nanocrystal physical properties allows us to demonstrate all solid‐state dye‐sensitized devices based on a commercial benchmark materials (organic indoline dye and molecular hole transporter) presenting state‐of‐the‐art performance comparable with reference devices based on a commercial TiO₂ paste. In particular, a drastic improvement in pore infiltration, which is found to balance a relatively lower surface area compared to the reference electrode, is evidenced using laser‐synthesized nanocrystals resulting in an improved short‐circuit current density under full sunlight. Transient photovoltage decay measurements suggest that charge recombination kinetics still limit device performance. However, the proposed strategy emphasizes the potentialities of the laser pyrolysis technique for up‐scaling nanoporous TiO₂ electrodes for various applications, especially for solar energy conversion.     

Design and Fabrication of a Precious Metal‐Free Tandem Core–Shell p+n Si/W‐Doped BiVO4 Photoanode for Unassisted Water Splitting

Tandem photoelectrochemical water splitting cells utilizing crystalline Si and metal oxide photoabsorbers are promising for low‐cost solar hydrogen production. This study presents a device design and a scalable fabrication scheme for a tandem heterostructure photoanode: p⁺n black silicon (Si)/SnO₂ interface/W‐doped bismuth vanadate (BiVO₄)/cobalt phosphate (CoPi) catalyst. The black‐Si not only provides a substantial photovoltage of 550 mV, but it also serves as a conductive scaffold to decrease charge transport pathlengths within the W‐doped BiVO₄ shell. When coupled with cobalt phosphide (CoP) nanoparticles as hydrogen evolution catalysts, the device demonstrates spontaneous water splitting without employing any precious metals, achieving an average solar‐to‐hydrogen efficiency of 0.45% over the course of an hour at pH 7. This fabrication scheme offers the modularity to optimize individual cell components, e.g., Si nanowire dimensions and metal oxide film thickness, involving steps that are compatible with fabricating monolithic devices. This design is general in nature and can be readily adapted to novel, higher performance semiconducting materials beyond BiVO₄ as they become available, which will accelerate the process of device realization.     

Nitrogen‐Doped Carbon‐Coated CuO‐In2O3 p–n Heterojunction for Remarkable Photocatalytic Hydrogen Evolution

CuO as a catalyst has shown promising application prospects in photocatalytic splitting of water into hydrogen (H₂). However, the instability of CuO in amine aqueous solution limits the applications of CuO‐based photocatalysts in the photocatalytic H₂ evolution. In this work, a novel dodecahedral nitrogen (N)‐doped carbon (C) coated CuO‐In₂O₃ p–n heterojunction (DNCPH) is designed and synthesized by directly pyrolyzing benzimidazole‐modified dodecahedral Cu/In‐based metal‐organic frameworks, showing long‐term stability in triethanolamine (TEOA) aqueous solution and excellent photocatalytic H₂ production efficiency. The improved stability of DNCPH in TEOA solution is ascribed to the alleviation of electron deficiency in CuO by forming the p–n heterojunction and the protection with coated N‐doped C layer. Based on detailed theoretical calculations and experimental studies, it is found that the improved separation efficiency of photogenerated electron/hole pairs and the mediated adsorption behavior (|?G_H*|→0) by coupling N‐doped C layer with CuO‐In₂O₃ p–n heterojunction lead to the excellent photocatalytic H₂ production efficiency of DNCPH. This work provides a feasible strategy for effectively applying CuO‐based photocatalysts in photocatalytic H₂ production.     

High‐Energy,High‐Rate,Lithium–Sulfur Batteries: Synergetic Effect of Hollow TiO2‐Webbed Carbon Nanotubes and a Dual Functional Carbon‐Paper Interlayer

A novel nanocomposite cathode consisting of sulfur and hollow‐mesoporous titania (HMT) embedded within carbon nanotubes (CNT), which is designated as S‐HMT@CNT, has been obtained by encapsulating elemental sulfur into the pores of hollow‐mesoporous, spherical TiO₂ particles that are connected via CNT. A carbon‐paper interlayer, referred to as dual functional porous carbon wall (DF‐PCW), has been obtained by filling the voids in TiO₂ spheres with carbon and then etching the TiO₂ template with a chemical process. The DF‐PCW interlayer provides a medium for scavenging the lithium polysulfides and suppressing them from diffusing to the anode side when it is inserted between the sulfur cathode and the separator. Lithium–sulfur cells fabricated with the thus prepared S‐HMT@CNT cathode and the DF‐PCW interlayer exhibit superior performance due to the containment of sulfur in TiO₂ and improved lithium–ion and electron transports. The Li–S cells display high capacity with excellent capacity retention at rates as high as 1C, 2C, and 5C rates.     

(040)‐Crystal Facet Engineering of BiVO4 Plate Photoanodes for Solar Fuel Production

A (040)‐crystal facet engineered BiVO₄ ((040)‐BVO) photoanode is investigated for solar fuel production. The (040)‐BVO photoanode is favorable for improved charge carrier mobility and high photocatalytic active sites for solar light energy conversion. This crystal facet design of the (040)‐BVO photoanode leads to an increase in the energy conversion efficiency for solar fuel production and an enhancement of the oxygen evolution rate. The photocurrent density of the (040)‐BVO photoanode is determined to be 0.94 mA cm^?2 under AM 1.5 G illumination and produces 42.1% of the absorbed photon‐to‐current conversion efficiency at 1.23 V (vs RHE, reversible hydrogen electrode). The enhanced charge separation efficiency and improved charge injection efficiency driven by (040) facet can produce hydrogen with 0.02 mmol h^?1 at 1.23 V. The correlation between the (040)‐BVO photoanode and the solar fuel production is investigated. The results provide a promising approach for the development of solar fuel production using a BiVO₄ photoanode.     

Strong Visible‐Light Absorption and Hot‐Carrier Injection in TiO2/SrRuO3 Heterostructures

Correlated electron oxides prove a diverse landscape of exotic materials' phenomena and properties. One example of such a correlated oxide material is strontium ruthenate (SrRuO₃) which is known to be a metallic itinerant ferromagnet and for its widespread utility as a conducting electrode in oxide heterostructures. We observe that the complex electronic structure of SrRuO₃ is also responsible for unexpected optical properties including high absorption across the visible spectrum (commensurate with a low band gap semiconductor) and remarkably low reflection compared to traditional metals. By coupling this material to a wide band gap semiconductor (TiO₂) we demonstrate dramatically enhanced visible light absorption and large photocatalytic activities. The devices function by photo‐excited hot‐carrier injection from the SrRuO₃ to the TiO₂ and the effect is enhanced in thin films due to electronic structure changes. This observation provides an exciting new approach to the challenge of designing visible‐light photosensitive materials.     

Fullerene as a Photoelectron Transfer Promoter Enabling Stable TiO2‐Protected Sb2Se3 Photocathodes for Photo‐Electrochemical Water Splitting

Understanding the degradation mechanisms of photoelectrodes and improving their stability are essential for fully realizing solar‐to‐hydrogen conversion via photo‐electrochemical (PEC) devices. Although amorphous TiO₂ layers have been widely employed as a protective layer on top of p‐type semiconductors to implement durable photocathodes, gradual photocurrent degradation is still unavoidable. This study elucidates the photocurrent degradation mechanisms of TiO₂‐protected Sb₂Se₃ photocathodes and proposes a novel interface‐modification methodology in which fullerene (C₆₀) is introduced as a photoelectron transfer promoter for significantly enhancing long‐term stability. It is demonstrated that the accumulation of photogenerated electrons at the surface of the TiO₂ layer induces the reductive dissolution of TiO₂, accompanied by photocurrent degradation. In addition, the insertion of the C₆₀ photoelectron transfer promoter at the Pt/TiO₂ interface facilitates the rapid transfer of photogenerated electrons out of the TiO₂ layer, thereby yielding enhanced stability. The Pt/C₆₀/TiO₂/Sb₂Se₃ device exhibits a high photocurrent density of 17 mA cm^?2 and outstanding stability over 10 h of operation, representing the best PEC performance and long‐term stability compared with previously reported Sb₂Se₃‐based photocathodes. This research not only provides in‐depth understanding of the degradation mechanisms of TiO₂‐protected photocathodes, but also suggests a new direction to achieve durable photocathodes for photo‐electrochemical water splitting.     

Outstanding Performance of Hole‐Blocking Layer‐Free Perovskite Solar Cell Using Hierarchically Porous Fluorine‐Doped Tin Oxide Substrate

Perovskite solar cells (PSCs) are of great interest in current photovoltaic research due to their extraordinary power conversion efficiency of ≈20% and boundless potentialities. The high efficiency has been mostly obtained from TiO₂‐based PSCs, where TiO₂ is utilized as a hole‐blocking, mesoporous layer. However, trapped charges and the light‐induced photocatalytic effect of TiO₂ seriously degrade the perovskite and preclude PSCs from being immediately commercialized. Herein, a simplified PSC is successfully fabricated by eliminating the problematic TiO₂ layers, using instead a fluorine‐doped tin oxide (FTO)/perovskite/hole–conductor/Au design. Simultaneously, the sluggish charge extraction at the FTO/perovskite interface is overcome by modifying the surface of the FTO to a porous structure using electrochemical etching. This surface engineering enables a substantial increase in the photocurrent density and mitigation of the hysteretic behavior of the pristine FTO‐based PSC; a remarkable 19.22% efficiency with a low level of hysteresis is obtained. This performance is closely approaching that of conventional PSCs and may facilitate their commercialization due to improved convenience, lower cost, greater stability, and potentially more efficient mass production.     

Amorphous Carbon Coated High Grain Boundary Density Dual Phase Li4Ti5O12‐TiO2: A Nanocomposite Anode Material for Li‐Ion Batteries

This work introduces an effective, inexpensive, and large‐scale production approach to the synthesis of a carbon coated, high grain boundary density, dual phase Li₄Ti₅O₁₂‐TiO₂ nanocomposite anode material for use in rechargeable lithium‐ion batteries. The microstructure and morphology of the Li₄Ti₅O₁₂‐TiO₂‐C product were characterized systematically. The Li₄Ti₅O₁₂‐TiO₂‐C nanocomposite electrode yielded good electrochemical performance in terms of high capacity (166 mAh g^?1 at a current density of 0.5 C), good cycling stability, and excellent rate capability (110 mAh g^?1 at a current density of 10 C up to 100 cycles). The likely contributing factors to the excellent electrochemical performance of the Li₄Ti₅O₁₂‐TiO₂‐C nanocomposite could be related to the improved morphology, including the presence of high grain boundary density among the nanoparticles, carbon layering on each nanocrystal, and grain boundary interface areas embedded in a carbon matrix, where electronic transport properties were tuned by interfacial design and by varying the spacing of interfaces down to the nanoscale regime, in which the grain boundary interface embedded carbon matrix can store electrolyte and allows more channels for the Li+ ion insertion/extraction reaction. This research suggests that carbon‐coated dual phase Li₄Ti₅O₁₂‐TiO₂ nanocomposites could be suitable for use as a high rate performance anode material for lithium‐ion batteries.     

In Situ Phase‐Induced Spatial Charge Separation in Core–Shell Oxynitride Nanocube Heterojunctions Realizing Robust Solar Water Splitting

Efficient spatial charge separation is critical for solar energy conversion over solid photocatalysts. The development of efficient visible‐light photocatalysts has been of immense interest, but with limited success. Here, multiband core–shell oxynitride nanocube heterojunctions composed of a tantalum nitride (Ta₃N₅) core and nitrogen‐doped sodium tantalate (NaTaON) shell have been constructed via an in situ phase‐induced etching chemical strategy. The photocatalytic water splitting performance of sub‐20‐nm Ta₃N₅@NaTaON junctions exhibits an extraordinarily high photocatalytic activity toward oxygen and hydrogen evolution. Most importantly, the combined experimental results and theoretical calculations reveal that the strong interfacial Ta? O? N bonding connection as a touchstone among Ta₃N₅@NaTaON junctions provides a continuous charge transport pathway rather than a random charge accumulation. The prolonged photoexcited charge carrier lifetime and suitable band matching between the Ta₃N₅ core and NaTaON shell facilitate the separation of photoinduced electron–hole pairs, accounting for the highly efficient photocatalytic performance. This work establishes the use of (oxy)nitride heterojunctions as viable photocatalysts for the conversion of solar energy into fuels.