Photoelectrocatalytic Research Articles

Recent progress in ammonia synthesis based on photoelectrocatalysis

Photoelectrocatalytic NH3 synthesis from N2 and H2O is a promising approach for N-neutralization goal based on catalytic strategies, such as vacancy engineering, ion doping, frustrated Lewis pair design, heterojunction construction, etc.

Construction of a novel Cu1.8S/NH2–La MOFs decorated Black-TNTs photoanode electrode for high-efficiently photoelectrocatalytic degradation of 2, 4-dichlorophenol

Photoelectrocatalysis (PEC) has long been regarded as an efficient and green method to eliminate various organic pollutants from wastewater. However, the lack of highly photoelectrocatalytic active and stable electrodes limits the development of the PEC technologies. Herein, a novel hierarchical photo-electrode with hollow Cu1.8S/NH2–La MOFs decorated black titanium dioxide nanotubes (Cu1.8S/NH2–La MOFs/Black TNTs) was fabricated by a two-step water-heating method. The prepared photoelectrode was used to degradation of 2, 4-dichlorophenol (2, 4-DCP). Analysis of photoelectrocatalytic degradation process of 2, 4-DCP was evaluated using UV–Vis absorption spectroscopy and the main degradation paths were analyzed by LC-MS. The results showed that 99.3% of the pollutant could be rapidly degraded within 180 min. Furthermore, the Cu1.8S/NH2–La MOFs/Black TNTs photoelectric pole exhibited excellent stability after 15 cycling experiments.

Self-supporting Cu9S5@nanoporous copper heterogenous photoanodes for efficient photoelectrocatalytic degradation

Self-supporting Cu9S5@nanoporous copper (Cu9S5@NPC) heterogenous photoelectrodes with controllable morphologies and hierarchical porous structures are synthesized through dealloying and anodization strategy. 3D Cu9S5 nanostructures (nanosheets or nanorods) grown in-situ on the surface of nanoporous copper (NPC) network are affected by the concentration ratio of Na2S and NaOH in the mixed aqueous solutions. It is found that lower Na2S concentration induces the formation of nanosheets. Attributing to the fertile porous channels, self-supporting structures as well as synergistic effect of Cu9S5 and NPC, the Cu9S5@NPC photoelectrodes possess outstanding photoelectrocatalytic (PEC) performance for the degradation of Methylene blue (MB) dye at the bias of 0.5 V under visible irradiation. Moreover, the possible PEC mechanism is further investigated.

Direct Z-Scheme Heterojunction α-MnO2/BiOI with Oxygen-Rich Vacancies Enhanced Photoelectrocatalytic Degradation of Organic Pollutants under Visible Light

The degradation efficiency of photoelectrocatalytic (PEC) processes for the removal of organic pollutants is highly dependent on the performance of the photoelectroanode catalyst. The design of PEC systems with a direct Z-scheme charge transfer mechanism and visible light excitation is essential to enhance the degradation efficiency of organic compounds. Here, a α-MnO2/BiOI direct Z-scheme heterojunction photocatalyst was successfully synthesized through a convenient and feasible method. It is remarkable that the photoanode exhibited excellent PEC performance under visible light irradiation; a 95% removal rate of tetracycline (TC) pollutants was achieved within 2 h, and it had excellent stability and reusability, which was expected to degrade antibiotics efficiently and environmentally in harsh environments. The presence of oxygen vacancies (OVs) in the α-MnO2/BiOI heterojunction was confirmed by electron spin resonance technique, and the OVs acted as electron traps that contributed substantially to the separation efficiency of photogenerated carriers. ESR characterization showed that the main reactive radicals during TC degradation were •OH and •O2−. By analyzing the intermediates, the possible degradation pathways of TC were further analyzed and a suitable degradation mechanism was proposed. The toxicity changes in the degradation process were explored by evaluating the toxicity of the intermediates. This study provides a new way to enhance the performance of Bi-based semiconductor photocatalysts for the effective degradation of TC in water.

Visible-light-responsive BiVO4/NH2-MIL-125(Ti) Z-scheme heterojunctions with enhanced photoelectrocatalytic degradation of phenol

BiVO4 is currently recognized as one of the most promising photoanodes for the remediation of organic pollutants. However, the poor charge transport ability of pure BiVO4 limits its quantum efficiency. Herein, to address this issue, a novel Z-scheme BiVO4/NH2-MIL-125(Ti) (BiVO4/NM125) heterojunction photoanode was successfully constructed through a one-step solvothermal process, and its physicochemical properties were characterized by various analytical techniques. After 150 min of irradiation, the optimum BiVO4/NM125 photoanode exhibited excellent degradation efficiency toward phenol (96.5 %) in comparison to single BiVO4 or NM125 at a bias of 2.0 V. The outstanding photoelectrocatalysis (PEC) activity was mainly owed to the promoted charge separation and migration efficiency, which was demonstrated by optical and photoelectrochemical measurements. The h+, •OH and O2•− were responsible for the degradation of both phenol and p-benzoquinone, as confirmed by radical scavenger experiments. After five cycles, the BiVO4/NM125 photoanode exhibited good stability with slight activity attenuation. The Z-scheme charge transfer mechanism was favorable for enhancing PEC activity instead of the type-Ⅱ mechanism. This work offers a new way for the construction of novel BiVO4–based Z-scheme heterojunction photoanodes for the degradation of phenol-containing wastewaters.

Oxygen-incorporated carbon nitride porous nanosheets for highly efficient photoelectrocatalytic CO2 reduction to formate

Using CO2 as a renewable carbon source for the production of high-value-added fuels and chemicals has recently received global attention. The photoelectrocatalytic (PEC) CO2 reduction reaction (CO2RR) is one of the most realistic and attractive ways of achieving this, and can be realized effectively under sunlight illumination at a low overpotential. Oxygen-incorporated carbon nitride porous nanosheets (CNs) were synthesized from urea or melamine by annealing in nitrogen or N2/O2 gas mixtures. They were used as the photoanode with Bi2CuO4 as the photocathode to realize PEC CO2 reduction to the formate. The electrical conductivity and the photoelectric response of the CNs were modified by changing the oxygen source. Oxygen in CNs obtained from an oxygen-containing precursor improved the conductivity because of its greater electronegativity, whereas oxygen in CNs obtained from the calcination atmosphere had a lower photoelectric response due to a down shift of the energy band structure. The CN prepared by annealing urea, which served as the source of oxygen and nitrogen, at 550 °C for 2 h in nitrogen is the best. It has a photocurrent density of 587 μA cm−2 and an activity of PEC CO2 reduction to the formate of 273.56 μmol cm−2 h−1, which is nearly 19 times higher than a conventional sample. The CN sample shows excellent stability with the photocurrent remaining constant for 24 h. This work provides a new way to achieve efficient catalysts for PEC CO2 reduction to the formate, which may be expanded to different PEC reactions using different cathode catalysts.

Photocatalytic and photoelectrocatalytic H2 evolution combined with valuable furfural production

In this work the photocatalytic (PC) and photoelectrocatalytic (PEC) reforming of furfuryl alcohol (FA) under environmental friendly conditions was investigated. Both H2 evolution and partial oxidation to furfuraldehyde were followed. For the first time TiO2 based photocatalysts were studied and the photocatalytic activity of home prepared photocatalysts was compared with that of commercial ones under both UVA and simulated solar irradiation. PEC tests were performed by using home prepared TiO2 nanotubes (TiO2 NTs) as photoanode and Pt free Ni foam as cathode to improve the Hydrogen Evolution Reaction (HER). Both the partial FA oxidation reaction rate and H2 evolution rate were normalized for the lamp specific power to account for the different photon flux and the rates were higher for PEC process. PEC is a promising strategy for the valorization of biomasses with simultaneous H2 production in spite of the cost of the bias.

Boosting generation of reactive oxygen and chlorine species on TNT photoanode and Ni/graphite fiber cathode towards efficient oxidation of ammonia wastewater

Photoelectrocatalytic (PEC) process combining the merits of photocatalysis and electrocatalysis is considered as a promising ammonia oxidation technology for water treatment. However, some key issues, such as the limited in situ generation of oxidants on photoanode, slow mass transfer problem and generation of nitrate/nitrite by–products hinder the further application of PEC process in the treatment of ammonia pollutant. In this study, the graphite felt (GF) cathodes modified by different transition metals (Ni, Fe, Mn, Co, Cu) were screened by physicochemical and photoelectrochemical characterizations. The results show that the Ni–GF cathode with more Ni0 uniformly distributed on the GF surface had the best electrocatalytic activity to generate H2O2. The PEC system composed of 10.0 wt% Ni–GF cathode and optimized titania nanotubes (TNTs) photoanode selectively converted about 96.1% ammonia to N2 within 90 min. Compared with the single TNTs photoanode system, the ammonia oxidation reaction rate constant of the synergistic PEC oxidation system was increased by about two times, which demonstrated the role of the oxidants simultaneously generated on both anode and cathode. The in situ generated reactive oxygen-based oxidants and chlorine-based oxidants interacted together, and ClO• acted a leading role in the ammonia oxidation which were confirmed by quenching and probe experiments. In addition, the contributions of •OH and ClO• were significantly improved in the synergistic PEC oxidation system, compared with the single TNTs photoanode system. Furthermore, the nitrate by–products generated by the ammonia oxidation were further reduced on the Ni–GF cathode. The large amount of active chlorine and active oxygen generated on the electrode diffused into the bulk, effectively overcoming the mass transfer limitation of direct oxidation. Therefore, the developed TNTs photoanode/Ni-GF cathode system can continuously and efficiently convert ammonia to N2 without the formation of nitrate/nitrite by–products.

Constructing Z-scheme NiMoO4@Co3O4 core-shell heterogeneous architectures with prominent photoelectrocatalytic performance toward water purification

Photoelectrocatalysis (PEC) oxidation is an efficient and eco-friendly advanced oxidation process (AOP), which is a hot research topic in the treatment of organic wastewater. The selection of superior photoelectrode materials is the critical factor affecting PEC efficiency and the main challenge in practical application. In this work, novel NiMoO4@Co3O4 hierarchical core-shell heterogeneous photoanodes were prepared through a two-step hydrothermal method and exhibited superior catalytic performance in the degradation of reactive brilliant blue KN-R. The wrapping of NiMoO4 nanosheets on Co3O4 nanowires electrode can enlarge its contact area with electrolyte, enable fast redox reaction and improve the long-term durability. The unique Z-scheme heterojunction structure between the two components ensured the effective separation of photo-generated carriers, facilitating the generation of OH and O2- during the PEC degradation process. The optimal NiMoO4@Co3O4-1.25 hierarchical architecture anode catalyst exhibited the highest removal rate of 83.65% of reactive brilliant blue KN-R in 120 min with long-term stability (∼12000 s) in 1.0 mol·L-1 H2SO4 solution. This report may inspire the design and fabrication of heterostructure photoanode in water purification.

In situ recombination for durable photoelectrocatalytic degradation of organic dye in wastewater

Photoelectrocatalysis (PEC) can effectively degrade organic pollutants by using photoelectrodes without secondary pollution. However, significant mass transport resistance and decreased catalytic activity caused by the shedding of active components remain a barrier to achieving the photocatalytic system with a high degradation rate and long-term durability. Here, an in situ recombination concept is presented to overcome this challenge. The bionic coral-like electrode, obtained by in situ assembly of UIO-66 around TiO2 nanoflowers (TNF) on Ti-foam substrate, is employed as the photoanode in PEC. Ex situ evaluation of photoelectrochemical activity demonstrates that the UIO-66@TNF/Ti-foam (U@T/T) design significantly improves the light-propagation, light-absorption and charge transfer. In Situ degradation evaluations also shows that the interesting design promotes rapid and stable degradation of organic dye (e.g. Rhodamine B (RhB)). At 2.0 V of bias potential and pH 7.0 in 5 mg L−1 RhB, under the action of active species such as ·O2- and ·OH (proved by the degradation mechanism experiments), the removal rate of RhB can reach 96.1% at 120 min and almost complete removal at 200 min (99.1%).

Enhanced visible light photoelectrocatalytic degradation of o-chloronitrobenzene through surface plasmonic Au nanoparticles and g-C3N4 co-modified TiO2 nanotube arrays photoanode

Chloronitrobenzenes are typical refractory aromatic halogenated nitroaromatic and high-toxic contaminants. The reduction process of chloronitrobenzenes cannot realize their mineralization, and the existence of chlorine group is detrimental to degradation through single chemical oxidation technology. Herein, the Au nanoparticles and graphitic carbon nitride co-modified TiO2 nanotube arrays (Au/g-C3N4/TNAs) photoanodes were fabricated to degrade o-chloronitrobenzene (o-CNB) target pollutant in photoelectrocatalytic (PEC) system. The Au/g-C3N4/TNAs fabricated with 0.20 mM HAuCl40.4 H2O (Au/g-C3N4/TNAs-0.20) had more superior optical and photoelectrochemical properties than other fabricated photoanodes. Au/g-C3N4/TNAs-0.20 photoanode increased dechlorination efficiency through reduction process, which was beneficial to o-CNB degradation and TOC removal. The coexistence of anions and humic acid inhibited the PEC degradation of o-CNB. The photogenerated electron, •O2−, hole and •OH participated in o-CNB degradation in PEC system. The degradation pathway of o-CNB was inferred through GC-MS spectra and DFT calculation. The acute toxicity and bioaccumulation factor of o-CNB were effectively reduced by PEC degradation.

Solar light responsive 2D/2D BiVO4/SnS2 nanocomposite for photocatalytic elimination of recalcitrant antibiotics and photoelectrocatalytic water splitting with high performance

A hydrothermal approach (environmentally safe route) was followed to synthesize eco-friendly, non-toxic, sunlight responsive 2D/2D BiVO4/SnS2 (BVSNS) nanocomposites with varying mole ratios. BVSNS exhibits favorable band gap, high charge carrier mobility, good surface area, lower recombining capability rendering it highly efficient photocatalyst. The superiority of photocatalysts was then tested for the degradation of pharmaceutical pollutants, ofloxacin (oflox) and tetracycline (TC), and photoelectrocatalytic (PEC) water splitting under sunlight illumination. The 1:3 BiVO4:SnS2 (13BVSNS) composite had highest decomposition efficiency of 93.7 and 80.8 % with rate constants of 0.0164 and 0.010 min−1 for oflox and TC-degradation, respectively. The GC–MS analysis was also conducted to examine the intermediates and products formed during the photocatalytic degradation of TC. The PEC water splitting experiments revealed that 13BVSNS photoanode exhibited highest photocurrent density of 0.21 mA/cm2 at 1.23 V vs RHE. The Mott-Schottky experiments demonstrated flat band potential of -0.37 V at 1.23 V vs RHE for the 13BVSNS electrode. As a result, ∼21 µmolcm−2sec-1 of H2 was produced and electrode was stable for 6 h. Reusability studies (7 runs) were used to further examine the photocatalyst's efficacy, and post reaction characterization results justified that the materials are highly stable with a long life.

Degradation of nitrobenzene in 3D stack Z-scheme photoelectrocatalytic system: Degradation condition, pathway analysis and synergistic mechanism

As a representative pollutant with carcinogenesis, mutagenicity and teratogenicity, nitrobenzene (NB) has devastating harm to human health. Herein, a unique three-dimensional (3D) stack Z-scheme photoelectrocatalytic (PEC) system was built by self-assembled different photoelectrodes for efficient NB removal. The effect of initial NB, bias potential, pH and electrolyte concentration on NB removal efficiency were investigated. The intermediates and oxygen-active radicals were determined and analyzed by high performance liquid chromatography (HPLC), gas chromatography-mass spectrometry (GC-MS), density functional theory (DFT) and electron paramagnetic resonance (EPR) to propose the NB degradation pathways and mechanism. The results showed that holes were utilized to produce ·OH to oxidize NB on the photoanode surface, the electrons excited from photocathode could reduce NB under UV irradiation; thereafter, the reduction product (aniline) was oxidized to phenol to achieve mineralization by the synergistic effect of anode (oxidation) and cathode (reduction). 3D stack Z-scheme PEC system exhibited a high NB degradation efficiency of 98.18% after 90 min reaction and a mineralization efficiency of 75.08% at 150 min. With ECOSAR software, the system toxicity was speculated. This study has advantages in NB removal and provides direction for other refractory organics.

Efficient removal of bisphenol A and Cr(VI) simultaneously in an advanced redox photoelectrocatalytic system over dual 3D TiO2 photoelectrodes

An adventurous strategy on the premise of synergistic photoelectrocatalysis (PEC) system based on three-dimensional (3D) TiO2 is proposed to realize the simultaneous removal of BPA and Cr(VI). The TiO2 photoelectrode demonstrates a 3D configuration, meanwhile supplies a multilevel facet heterojunction (FH). The dual-FH-TiO2/Ti PEC system is constructed via the application of 3D FH-TiO2/Ti as both cathode and anode, where the redox efficiency of BPA and Cr(VI) increased by 1.07 and 4.28 times of the single system. The visible growth accounts for more exposure of active sites and a higher utilization of active species, proved by EPR and quenching experiments. In the practical wastewater, the removal efficiency of BPA and Cr(VI) reaches 97.04% and 81.18% in 1 h. The effects of various influence factors such as pH, electrolyte concentration and coexisting ions on BPA and Cr(VI) removal are studied for practical applications.

Investigation of photoelectrocatalytic degradation mechanism of methylene blue by α-Fe2O3 nanorods array

Efficiently and thoroughly degrading organic dyes in wastewater is of great importance and challenge. Herein, vertically oriented mesoporous α-Fe2O3 nanorods array (α-Fe2O3-NA) is directly grown on fluorine-doped tin oxide (FTO) glass and employed as the photoanode for photoelectrocatalytic degradation of methylene blue simulated dye wastewater. The Ov sites on the α-Fe2O3-NA surface are the active sites for methylene blue (MB) adsorption. Electrons transfer from the adsorbed MB to Fe-O is detected. Compared with electrocatalytic and photocatalytic degradation processes, the photoelectrocatalytic (PEC) process exhibited the best degrading performance and the largest kinetic constant. Hydroxyl, superoxide free radicals, and photo-generated holes play a jointly leading role in the PEC degradation. A possible degrading pathway is suggested by liquid chromatography-mass spectroscopy analysis. This work demonstrates that photoelectrocatalysis by α-Fe2O3-NA has a remarkable superiority over photocatalysis and electrocatalysis in MB degradation. The in-depth investigation of photoelectrocatalytic degradation mechanism in this study is meaningful for organic wastewater treatment.

An in-situ transient photo-induced voltage method to understand the PEC efficiency of C, N co-doped TiO2 photoanode

Photoelectrocatalysis (PEC) is one of the most important green energy conversion technologies. During the development of PEC, the Jabs, ηsep and ηinj are challenges that hinder the performance enhancement of different kinds of photoanodes in PEC systems. As a stable, cheap and non-toxic PEC material, TiO2 is also limited by the above challenges. Here, a series of C, N co-doped TiO2 photoanodes were synthesized by hydrothermal method combined with a simple one-step thermal diffusion treatment. Under AM 1.5 G light intensity, the PEC performance of TCN-1.5 is 4.06 mA cm−2 at 1.23 V vs RHE in 1.0 M NaOH, which is ca. 2.08 times as high as the photocurrent density of the pristine TiO2. Especially, an in-situ transient photoinduced voltage (TPV) method was developed to measure the changes on efficiencies mentioned above: Jabs, ηsep and ηinj are improved by about 9.8 %, 24.9 % and 48.3 %, respectively, and their product is equal to the increase of photocurrent density. This work analyzes the improvement of efficiencies in the PEC process through in-situ characterization and opens up a new way for PEC material design and fabrication.

Improvement of surface light absorption of ZnO photoanode using a double heterojunction with α–Fe2O3/g–C3N4 composite to enhance photoelectrochemical water splitting

This study investigated a double-heterojunction of a ZnO/α–Fe2O3/g–C3N4 photoanode to overcome each of their intrinsic drawbacks for use as photocatalysts or photoelectrocatalysts ZnO thin film having a wide bandgap and low reduction potential, α–Fe2O3 having insufficient reduction potential, and g–C3N4 having low oxidation potential as photocatalysts. The elemental and chemical mapping of the materials species and free metal ions were investigated for the first-time using time-of-flight–secondary ion mass spectrometry (TOF−SIMS), which is a surface-sensitive analytical method. The depth profile of TOF−SIMS indicated that the α–Fe2O3 and g–C3N4 species were homogeneously covered and chemically connected on the surface of ZnO nanorods. The photoelectrocatalytic (PEC) performance of the ZnO/α–Fe2O3/g–C3N4 photoanode was obtained, and it showed a photocurrent density of 0.97 mA/cm2 at 1.23 VRHE and under 100 mW/cm2 illumination, which was (1.6 and 4.8) fold greater than those of the ZnO/α–Fe2O3 and ZnO photoanode, respectively. The ZnO/α–Fe2O3/g–C3N4 photoanode generated 29.28 μmol/cm2 of H2 and 14.15 μmol/cm2 of O2 at 2 h illumination of 100 mW/cm2 light along with 1.23 VRHE. The inclusion of the dual heterojunction in the ZnO/α–Fe2O3/g–C3N4 photoanode provided lower charge transfer resistance (Rct) and higher electrochemical active surface area (ECSA), which led to simultaneous enhancements in the electron-hole separation and surface light absorption at higher wavelengths, ultimately resulting in substantially improved PEC performance.

Solar Hydrogen Fuel Generation from Wastewater—Beyond Photoelectrochemical Water Splitting: A Perspective

Green hydrogen—a carbon-free renewable fuel—has the capability to decarbonise a variety of sectors. The generation of green hydrogen is currently restricted to water electrolysers. The use of freshwater resources and critical raw materials, however, limits their use. Alternative water splitting methods for green hydrogen generation via photocatalysis and photoelectrocatalysis (PEC) have been explored in the past few decades; however, their commercial potential still remains unexploited due to the high hydrogen generation costs. Novel PEC-based simultaneous generation of green hydrogen and wastewater treatment/high-value product production is therefore seen as an alternative to conventional water splitting. Interestingly, the organic/inorganic pollutants in wastewater and biomass favourably act as electron donors and facilitate the dual-functional process of recovering green hydrogen while oxidising the organic matter. The generation of green hydrogen through the dual-functional PEC process opens up opportunities for a “circular economy”. It further enables the end-of-life commodities to be reused, recycled and resourced for a better life-cycle design while being economically viable for commercialisation. This review brings together and critically analyses the recent trends towards simultaneous wastewater treatment/biomass reforming while generating hydrogen gas by employing the PEC technology. We have briefly discussed the technical challenges associated with the tandem PEC process, new avenues, techno-economic feasibility and future directions towards achieving net neutrality.

Electrically conductive TiO2/CB/PVDF membranes for synchronous cross-flow filtration and solar photoelectrocatalysis

Combining photocatalysis (PC) and membrane filtration (MF) has emerged as an attractive technology for water purification, however, the water purification efficiency and membrane fouling are still challenging. Herein, we report a novel photoelectrocatalytic (PEC) membrane mediated by a ternary polyvinylidene fluoride (PVDF)-carbon black (CB)–TiO2 composite conductive membrane synthesized by a phase inversion method assisted by the mixed surfactants of polyvinylpyrrolidone (PVP) and sodium dodecyl sulfate (SDS). The resultant electrically conductive TiO2/CB/PVDF membrane features a homogeneous surface with obvious pore size of 20–150 nm, a thickness ∼116 μm, and an average resistivity as low as ∼3.165 Ω∙m. The cooperation of PVP and SDS surfactants dramatically improves the organic-inorganic interactions and thus eventually enhances the porosity, stability of porous structure, mechanical stability, and conductivity and electrochemical properties of the hybrid membrane. Upon the solvent evaperation of the wellblended casting solution and the phase inversion, TiO2/CB preferentially exist on the surface of PVDF membrane, enabling the efficient PEC degradation of organic pollutants. The synergistic coupling of TiO2 and CB in PVDF membrane results in efficient PEC properties with bi-functional membrane antifouling and enhanced water purification in azo dyes decolorization under the stationary mode and in our lab-made continuous cross-flow PEC system, superior to those by photocatalysis and electrocatalysis. The developed synchronous MF and PEC system mediated by the conductive TiO2/CB/PVDF membrane proves to a feasible route to improving the self-cleaning properties of the polymer membrane while simultaneously increasing the water decontaminating efficiency.

Novel Bi2Sn2O7 quantum dots/TiO2 nanotube arrays S-scheme heterojunction for enhanced photoelectrocatalytic degradation of sulfamethazine

The step-scheme (S-scheme) heterojunction of Bi2Sn2O7 quantum dots (QDs)/TiO2 nanotube arrays (NTAs) photoanodes were prepared for efficient and stable photoelectrocatalytic (PEC) degradation of sulfamethazine (SMT) at low potential and light-emitting diode (LED) illumination. In the Bi2Sn2O7/TiO2 NTAs system, the synergistic factor of photocatalysis (PC) and electrocatalysis (EC) reached 10.1. The elevated performance was attributed to improved light-harvest capability by the decorated TiO2 NTAs with Bi2Sn2O7 QDs, lower charge transfer resistance, more efficient photoexcited charge separation, and higher redox ability to produce photogenerated holes (h+) and reactive oxygen species (ROS) with great efficiency. The possible PEC mechanism of S-scheme Bi2Sn2O7/TiO2 NTAs was elucidated by experimental studies and density functional theory (DFT) calculations, which confirmed the establishment of the internal electric field (IEF) promoted carrier separation and transport. This research provides a feasible approach for fabricating superior PEC photoanodes as well as new insights into heterojunction design.