Heterojunction Photoelectrode Research Articles

A Type-II CQDs regulating FeOOH decorated BiVO4 photoelectrode for highly efficient photoelectrochemical degradation of tetracycline

Bismuth vanadate (BiVO4) photoelectrode is of great potentials to be used for photoelectrochemical (PEC) removal of antibiotic pollutant. However, it still suffers from lower efficiency. Herein, a type-II FeOOH-CQDs/BiVO4 photoelectrode was fabricated via the in-situ growth of FeOOH nanoparticles over BiVO4 using Carbon quantum dots (CQDs) as mediator. Benefiting from the type-II heterojunction between BiVO4 and FeOOH, as well as the excellent charger transfer assisted by CQDs, FeOOH-CQDs/BiVO4 exhibited excellent PEC degradation performance towards a typical antibiotic- tetracycline (TC). In a typical PEC process, FeOOH-CQDs/BiVO4 photoelectrode (2 cm × 2 cm) yielded a high removal ratio of ∼ 99 % toward TC within 120 min at an applied potential of 0.6 V (vs. Hg/Hg2Cl2). Moreover, the PEC configuration was verified to be used for TC degradation in actual waters, such as tap water and lake water, with > 90 % of removal ratio. The radical trapping experiments revealed holes and superoxide radical dominated in the TC degradation process. This work provides an insight on the type-II heterojunction photoelectrode to enhance the PEC degradation of TC, which would help for the treatment of antibiotic wastewater.

Accelerating photoelectrochemical CO2RR selectively of C2+ products by integrating Ag/Pd cocatalysts on Cu/Cu2O/CuO heterojunction nanorods

The Cu-based photoelectrochemical CO2 reduction reaction (PEC–CO2RR) represents a convenient approach for producing value-added C2+ products, aiming to achieve carbon neutrality by reducing greenhouse gas emissions. However, these reactions typically suffer from limited selectivity. In this work, we fabricate Cu/Cu2O/CuO nanorod (CuR)-based heterojunction architectures integrated with Ag and Pd cocatalysts to boost the selectivity of C2+ products. The proposed Cu/Cu2O/CuO/Ag-Pd (CuR/Ag-Pd) photoelectrodes are used as photocathodes to generate a maximum Faradaic efficiency (FE) of C2+ products exceeding 53% by suppressing the hydrogen evolution reaction (HER). The FE improvement is approximately 22-fold (n-propanol), 12-fold (ethanol), 13-fold (acetaldehyde), and 6-fold (acetate) compared with CuR photoelectrodes operating at a negative applied potential of −1.8 V (vs. reversible hydrogen electrode, RHE). Conversely, the CuR photoelectrodes exhibit a maximum HER rate of ∼86% at −1.8 V (vs. RHE), higher than those of the CuR/Ag (54%) and CuR/Ag-Pd (35%) photoelectrodes. The superior PEC–CO2RR performance of CuR/Ag-Pd photoelectrodes is attributable to the higher electrochemical active surface area (6.7 mF/cm2) and faster charge transfer rate at the electrode/electrolyte interface owing to the presence of cocatalysts. In addition, the CuR/Ag-Pd photoelectrodes exhibit remarkable long-term stability retaining 70% of the initial performance even after a relatively more negative applied potential at −1.2 V. A comprehensive investigation into the changes in surface morphology, crystal structure, and elemental composition after PEC–CO2RR confirms the higher stability of CuR/Ag-Pd photoelectrodes. Thus, this work provides novel perceptions into the development of Cu-based heterojunction photoelectrodes integrated with Ag/Pd cocatalysts for improving the selectivity of C2+ products.

Molecular and Heterojunction Device Engineering of Solution-Processed Conjugated Reticular Oligomers: Enhanced Photoelectrochemical Hydrogen Evolution through High-Effective Exciton Separation.

Covalent organic frameworks (COFs) face limited processability challenges as photoelectrodes in photoelectrochemical water reduction. Herein, sub-10nm benzothiazole-based colloidal conjugated reticular oligomers (CROs) are synthesized using an aqueous nanoreactor approach, and the end-capping molecular strategy to engineer electron-deficient units onto the periphery of a CRO nanocrystalline lattices (named CROs-Cg). This results in stable and processable "electronic inks" for flexible photoelectrodes. CRO-BtzTp-Cg and CRO-TtzTp-Cg expand the absorption spectrum into the infrared region and improve fluorescence lifetimes. Heterojunction device engineering is used to develop interlayer heterojunction and bulk heterojunction (BHJ) photoelectrodes with a hole transport layer, electron transport layer, and the main active layers, using a CROs/CROs-Cg or one-dimensional (1D) electron-donating polymer HP18 mixed solution via spinning coating. The ITO/CuI/CRO-TtzTp-Cg-HP18/SnO2/Pt photoelectrode shows a photocurrent of 94.9µA cm‒2 at 0.4V versus reversible hydrogen electrode (RHE),which is 47.5 times higher than that of ITO/Bulk-TtzTp. Density functional theory calculations show reduced energy barriers for generating adsorbed H* intermediates and increased electron affinity in CROs-Cg. Mott-Schottky and charge density difference analyses indicate enhanced charge carrier densities and accelerated charge transfer kinetics in BHJ devices. This study lays the groundwork for large-scale production of COF nanomembranes and heterojunction structures, offering the potential for cost-effective, printable energy systems.

BiVO4/CuBi2O4 heterojunction photoanodes with enhanced charge separation for efficient photoelectrochemical water splitting

BiVO4/CuBi2O4 photoanodes were fabricated by depositing CuBi2O4 layers on top of BiVO4 layers while employing a solution-based deposition technique. Carrier separation and transfer are facilitated by the heterojunction that forms between BiVO4 and CuBi2O4, which significantly raises carrier density. Time-resolved photoluminescence (TRPL), UV–VIS absorption spectra, scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) were employed for the characterization of the photoelectrode. The heterojunction photoelectrode demonstrated enhanced photoelectrochemical activity in comparison to BiVO4 alone, with the maximum photocurrent density of 1.15 mA/cm2 at 1.23 V vs. RHE. The improvement is attributed to decreased recombination of photo-generated electrons and holes and improved charge separation and transport in the heterostructure. By the generation of heterojunctions, the current work offers a new avenue for the design and construction of photoanodes with high charge separation efficiencies. This may be useful for the further enhancement of PEC water-splitting performances.

Metal-insulator-semiconductor photoelectrodes for enhanced photoelectrochemical water splitting.

Photoelectrochemical (PEC) water splitting provides a scalable and integrated platform to harness renewable solar energy for green hydrogen production. The practical implementation of PEC systems hinges on addressing three critical challenges: enhancing energy conversion efficiency, ensuring long-term stability, and achieving economic viability. Metal-insulator-semiconductor (MIS) heterojunction photoelectrodes have gained significant attention over the last decade for their ability to efficiently segregate photogenerated carriers and mitigate corrosion-induced semiconductor degradation. This review discusses the structural composition and interfacial intricacies of MIS photoelectrodes tailored for PEC water splitting. The application of MIS heterostructures across various semiconductor light-absorbing layers, including traditional photovoltaic-grade semiconductors, metal oxides, and emerging materials, is presented first. Subsequently, this review elucidates the reaction mechanisms and respective merits of vacuum and non-vacuum deposition techniques in the fabrication of the insulator layers. In the context of the metal layers, this review extends beyond the conventional scope, not only by introducing metal-based cocatalysts, but also by exploring the latest advancements in molecular and single-atom catalysts integrated within MIS photoelectrodes. Furthermore, a systematic summary of carrier transfer mechanisms and interface design principles of MIS photoelectrodes is presented, which are pivotal for optimizing energy band alignment and enhancing solar-to-chemical conversion efficiency within the PEC system. Finally, this review explores innovative derivative configurations of MIS photoelectrodes, including back-illuminated MIS photoelectrodes, inverted MIS photoelectrodes, tandem MIS photoelectrodes, and monolithically integrated wireless MIS photoelectrodes. These novel architectures address the limitations of traditional MIS structures by effectively coupling different functional modules, minimizing optical and ohmic losses, and mitigating recombination losses.

Bimetallic Ni–Co-ZIF derived (Ni, Co)Se2/BiVO4 heterojunction photoelectrodes with oxygen vacancy for enhancing PEC performance

Bismuth vanadate (BiVO4) still limits its practical application due to its poor water oxidation kinetics and easy surface charge recombination. In this paper, bimetallic Ni–Co-zeolitic imidazolate frameworks (Ni–Co-ZIF) was successfully transformed into metal oxides and selenides modified on the surface of BiVO4 ((Ni, Co)Se2/BiVO4) by electrostatic adsorption and pyrolytic selenization methods to further improve the photoelectrochemistry (PEC) performance of BiVO4. In the presence of (Ni,Co)Se2 layer, the best photocurrents of (Ni, Co)Se2/BiVO4 heterojunction photoelectrodes reached to 3.30 mA/cm2, which is better than the pure BiVO4 with about 4.07 times. The reason for PEC performance enhancement of (Ni, Co)Se2/BiVO4 since that the bimetallic (Ni,Co)Se2 with more metal active sites and oxygen vacancy takes advantage of the strong conductivity of charges to improve the charge separation and transfer efficiency. Meanwhile, these (Ni, Co)Se2/BiVO4 photoelectrodes have shown more stability in alkaline electrolyte solutions.

Enhanced photoelectrochemical performance of ZnO/α-Fe2O3 heterojunction photoelectrode fabricated by facile hydrothermal and spin-coating method

The present study reports the successful fabrication of ZnO/α-Fe2O3 heterojunctions by facile and simple hydrothermal and spin-coating methods. The effect of spin-coating different FeCl3 precursor layers on the photoelectrochemical performance has been investigated. Additionally, the procedure of spin-coating FeCl3 precursors was simulated by fluent software. It is noteworthy that ZnO/α-Fe2O3 heterojunctions increase the absorption of visible light, promote the separation and transfer of photogenerated charge carriers, reduce the interfacial resistance between the photoelectrode and electrolyte, and provide a larger electrochemically active contact area in contrast to pure ZnO nanorods. The highest photocurrent density and the highest IPCE (incident photon-to-current efficiency) reach 1.82 mA cm−2 and 40 % respectively when spin-coating three layers. Moreover, the mechanism of enhanced PEC performance was further discussed via EIS (electrochemical impedance spectroscopy), Mott-Schottky curves, Energy band structure diagram, and the electrochemical active surface area (ECSA) test.

Abnormal Photocurrent in Semiconductor p‐n Heterojunctions: Toward Multifunctional Photoelectrochemical‐Type Photonic Devices and Beyond

AbstractSemiconductor p‐n heterojunctions are important building blocks for modern electronic and photonic devices. Further combining semiconductor p‐n heterojunctions with light and electrolyte environment, interesting photoelectrochemical (PEC) phenomena can occur, which enriches the design principles of multifunctional devices. In fact, recent years have witnessed the emergence of PEC‐type photonic devices. For PEC‐type photonic devices, a key to realize multifunctionality is to control the photocurrent polarity of the photoelectrode. In this study, an abnormal photocurrent is reported from p‐InGaN/n‐GaN nanowire heterojunctions under a blue light illumination: although n‐GaN is transparent to the blue light (and thus optical absorption mainly occurs in p‐InGaN) and p‐InGaN in principle can only give negative PEC photocurrent, the detailed experiments show that positive PEC photocurrent can be generated from the p‐InGaN segment due to the existence of the built‐in electric field at the p‐n junction. This study shows a new route to control the photocurrent polarity in a semiconductor p‐n heterojunction photoelectrode. This unveiled role of the built‐in electric field is expected to impact the design of emerging PEC‐type photonic devices, as well as other novel photonic and electronic devices based on semiconductor nanowire p‐n heterojunctions.

Carbon Nitride-Based Heterojunction Photoelectrodes with Modulable Charge-Transfer Pathways toward Selective Biosensing.

Photoelectrochemical (PEC) sensing enables the rapid, accurate, and highly sensitive detection of biologically important chemicals. However, achieving high selectivity without external biological elements remains a challenge because the PEC reactions inherently have poor selectivity. Herein, we report a strategy to address this problem by regulating the charge-transfer pathways using polymeric carbon nitride (pCN)-based heterojunction photoelectrodes. Interestingly, because of redox reactions at different semiconductor/electrolyte interfaces with specific charge-transfer pathways, each analyte demonstrated a unique combination of photocurrent-change polarity. Based on this principle, a pCN-based PEC sensor for the highly selective sensing of ascorbic acid in serum against typical interferences, such as dopamine, glutathione, epinephrine, and citric acid was successfully developed. This study sheds light on a general PEC sensing strategy with high selectivity without biorecognition units by engineering charge-transfer pathways in heterojunctions on photoelectrodes.

Engineering interfacial band hole extraction on chemical-vapor-deposited MoS2/CdS core-shell heterojunction photoanode: The junction thickness effects on photoelectrochemical performance

Heterojunction fabrication is a promising strategy that can greatly boost the charge carrier separation and improve the solar-to-hydrogen conversion efficiency of photoelectrochemical (PEC) cells. However, such technology still suffers from limited contact interfaces. In this study, the chemical vapor deposition (CVD) technique was for the first time used to construct the CdS/MoS2 heterojunction photoanode with a unique core-shell nanoarchitecture, in which a continuous crystalline MoS2 nanosheet layer was grown directly on one-dimensional (1D) oriented CdS nanorods (NRs) in a plane-to-plane stacking fashion. The optimization of junction thickness with adjustable MoS2 loading from mono to a few layers was achieved by experimental parameters variation. Systematic characterizations show that the MoS2 shell plays a dual role as an optical absorption booster for more photo-exciton generation and a surface passivator of trap states. Meanwhile, the formed heterojunction helps regulate the unidirectional charge migration for a significantly suppressed electron-hole recombination process, which synergistically contributes to higher quantum yield and efficiency. As a result, the optimized CdS/MoS2 heterojunction photoanode with 3-layered MoS2 wrapping exhibits the highest photocurrent density and photoconversion efficiency, over a two-fold increase, compared to those of pristine CdS and the previously reported CdS/MoS2 heterojunctions. Moreover, due to the rapid hole extraction from CdS and transferred surface oxidation sites, the present CdS/MoS2 heterostructure demonstrates better corrosion resistance and higher photostability. The present work is expected to provide a versatile platform for exploiting the CVD technique to develop other MoS2-based heterojunction photoelectrodes with extensive PEC applications.

A Mo doping WO3/CdZnS heterojunction photoelectrode for boosting electron storage capacity

Most of the photoelectrodes for photoelectrochemical cathodic protection (PECCP) technology reported at present cannot store electrons, leading to the inability to protect metals in the absence of light, which becomes the main defect that limits the practical application of PECCP. In this work, a Mo doping WO3/CdZnS heterojunction photoelectrode with electrons storage capability was prepared, by which the PECCP can be kept running in the absence of light. The result of theoretical calculation of density functional validates that Mo doping can introduce new doping levels into WO3, leading to modifications in the intrinsic electronic structure associated with increasing capacitance and conductivity. The compounding of CdZnS can not only broaden the light absorption threshold of the photoelectrode, but also charge the Mo-WO3. Besides, the construction of heterojunction also facilitates the oriented separation and migration of photogenerated carriers. The 0.3%Mo-WO3/CdZnS-2 composite photoelectrode with desirable capacity of electron storage can store the quantity of electric charge about 1.87 × 10−3 C after 100 s illumination, which is about 1.5 times of WO3/CdZnS-2 without Mo doping. In the meanwhile, the persistent PECCP performance in the absence of light was also prolonged from 481 s to 584 s.

CuAlO2/CuBi2O4 heterojunction photocathodes with improved charge collection for efficient solar water splitting

P-type heterojunction photoelectrode made of CuAlO2 and CuBi2O4 has been developed for the first time by using solution-based deposition method. Its advantageous bandgap size and favourable band positions make it a highly prospective option for photoelectrochemical (PEC) water splitting. The photoelectrode was characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–vis absorption spectra, time-resolved photoluminescence (TRPL) and X-ray photoelectron spectroscopy (XPS). Compared to CuBi2O4 alone, the heterojunction photoelectrode showed improved photoelectrochemical activity with the highest photocurrent density of − 0.62 mA/cm2 at 0.6 V vs. RHE. The improvement is attributed to decreased recombination of photo-generated electrons and holes and improved charge separation and transport in the heterostructure. This research offers an efficient method to enhance the visible-light-driven activity of CuBi2O4 and a new strategy for fabricating heterogeneous nanostructure photoelectrodes for solar-driven water splitting.

Significantly boosted photoelectrochemical water splitting performance by plasmonic enhanced Hematite@MOF composite photoelectrodes

Hematite as a catalyst for photoelectrochemical water splitting offers huge potential, due to its high chemical stability, great abundance, and low cost. However, the low water oxidation kinetics and poor charge transportation have hindered progress towards the manufacture of practical water splitting devices. To tackle these problems, a visible light responsive metal-organic framework (MOF) polyhedral zeolitic imidazolate (ZIF-67), and optimised plasmonic Ag nanorods were incorporated into hematite nanostructures to form a three-component heterojunction photoelectrode. The designed photoanode showed dramatically improved light harvesting in the visible range and enhanced charge transport. A mechanistic investigation allowed the deconvolution of the enhanced performance pathways. First, the Hematite@ZIF-67 core-shell p-n junction enables facile charge carrier transfer between ZIF-67 and hematite. In addition, ZIF-67 also provides active sites for water oxidation and boosts surface oxygen evolution reaction (OER) kinetics. Guided by finite-difference time-domain (FDTD) modelling, Ag nanorods with optimised aspect ratio were incorporated between ZIF-67 and hematite. The Ag nanorods facilitate broadband light absorption and surface charge injection, induced by near-field excitation enhancement and plasmonic resonance energy transfer (PRET) pathways. The design and addition of ZIF-67 and Ag nanorods result in superior performance for a hematite-based photoanode for photoelectrochemical (PEC) water oxidation.

Charge transport dynamics of a C6H4NH2CuBr2I/TiO2 heterojunction in aqueous solution under reverse bias.

The photocurrent output of the C6H4NH2CuBr2I/TiO2 heterojunction photoelectrode in an aqueous solution is super stable even after 30 000 s. However, the photocurrent is extremely weak. Intensity-modulated photocurrent spectroscopy revealed that the electron transfer in the C6H4NH2CuBr2I/TiO2 photoelectrode without bias is not sufficiently fast to compete with the charge recombination process due to the short diffusion length (∼23 nm), resulting in a low photocurrent. The charge separation and charge transfer efficiency in the bulk of C6H4NH2CuBr2I could be significantly improved under a small reverse electric field (Er), resulting in an enhanced photocurrent.

High-performance Vo-ZnO/ZnS benefiting nanoarchitectonics from the synergism between defect engineering and surface engineering for photoelectrochemical glucose sensors.

In this study, a ZnO/ZnS nanocluster heterojunction photoelectrode rich in surface oxygen defects (Vo-ZnO/ZnS) was prepared by applying a simple in situ anion substitution and nitrogen atmosphere annealing method. The synergism between defect and surface engineering significantly improved the photocatalysts. Given this synergism, Vo-ZnO/ZnS was endowed with a long carrier lifetime, narrow band gap, high carrier density, and high performance toward electron transfer under light conditions. Thus, Vo-ZnO/ZnS had three times the photocurrent density of ZnO under light illumination. To further evaluate its advantages in the field of photoelectric bioassay, Vo-ZnO/ZnS was applied as the photocathode of photoelectric sensor system for glucose detection. Vo-ZnO/ZnS showed excellent performance in glucose detection in various aspects, including a low detection limit, high detection sensitivity, and a wide detection range.

Electrodeposition of Copper Oxides as Cost-Effective Heterojunction Photoelectrode Materials for Solar Water Splitting

Photoelectrocatalytic hydrogen production is crucial to reducing greenhouse gas emissions for carbon neutrality and meeting energy demands. Pivotal advances in photoelectrochemical (PEC) water splitting have been achieved by increasing solar light absorption. P-type Cu-based metal oxide materials have a wide range of energy band gaps and outstanding band edges for PEC water splitting. In this study, we first prepared Cu2O thin films using electrodeposition and fabricated a heterojunction structure of CuO/Cu2O by controlling annealing temperatures. The surface morphological, optical, and electrochemical properties were characterized using various analytical tools. X-ray and Raman spectroscopic approaches were used to verify the heterojunction of CuO/Cu2O, while surface analyses revealed surface roughness changes in thin films as the annealing temperatures increased. Electrochemical impedance spectroscopic measurements in conjunction with the Mott–Schottky analysis confirm that the CuO/Cu2O heterojunction thin film can boost photocurrent generation (1.03 mA/cm2 at 0 V vs. RHE) via enhanced light absorption, a higher carrier density, and a higher flat band potential than CuO and Cu2O thin films (0.92 and 0.08 mA/cm2, respectively).

Constructing NCuS Interface Chemical Bonds over SnS2 for Efficient Solar-Driven Photoelectrochemical Water Splitting.

The restricted charge transfer and slow oxygen evolution reaction (OER) dynamics tremendously hamper the realistic implementation of SnS2 photoanodes for photoelectrochemical (PEC) water splitting. Here, a novel strategy is developed to construct interfacial NCuS bonds between NC skeletons and SnS2 (CuNC@SnS2 ) for efficient PEC water splitting. Compared with SnS2 , the PEC activity of CuNC@SnS2 photoelectrode is tremendously heightened, obtaining a current density of 3.40 mA cm2 at 1.23 VRHE with a negatively shifted onset potential of 0.04 VRHE , which is 6.54 times higher than that of SnS2 . The detailed experimental characterizations and theoretical calculation demonstrate that the interfacial NCuS bonds enhance the OER kinetic, reduce the surface overpotential, facilitate the separation of photon-generated carriers, and provide a fast transmission channel for electrons. This work presents a new approach for modulating charge transfer by interfacial bond design in heterojunction photoelectrodes toward promoting PEC performance and solar energy application.

Improved photostability of CuO by using WO3/CuO and BiVO4/WO3/CuO heterojunction photoelectrodes with various thermal annealing processes

In this study, WO3/CuO and BiVO4/WO3/CuO heterojunction photoelectrodes were fabricated to improve the photoelectrochemical properties of CuO photoelectrodes. Regarding the WO3/CuO photoelectrodes, we investigated the effects of thermal annealing after CuO growth and annealing temperature after depositing WO3 on CuO. The sample annealed at 400 °C after WO3 deposition and without annealing after CuO growth had a higher photocurrent density than the CuO photoelectrode; however, it still had a low photostability of 37 %. Regarding the BiVO4/WO3/CuO photoelectrodes, we investigated the effects of annealing on WO3/CuO and the annealing temperature and duration after BiVO4 deposition. Accordingly, we found that the light absorbance, full width at half maximum of the CuO XRD (020) peak, flat-band potential, acceptor density, and charge transfer resistance were highly dependent on the annealing duration of BiVO4. Moreover, a large improvement in photoelectrochemical properties was obtained by fabricating BiVO4/WO3/CuO heterojunction photoelectrodes via a proper annealing process. As a result, a very high photostability of 78 % was obtained from the BiVO4/WO3/CuO photoelectrode that was annealed at 400 °C for 20 minutes only after BiVO4 deposition without annealing after CuO and WO3 depositions, which was much higher than the 21 % photostability of the CuO photoelectrode.

Ligand‐Engineered Quantum Dots Decorated Heterojunction Photoelectrodes for Self‐Biased Solar Water Splitting (Small 46/2022)

Bias-Free Water Splitting In article number 2204495, Xin Tong, Lianzhou Wang, Zhiming M. Wang, and co-workers develop a quantum dots (QDs)-based photoelectrochemical (PEC) device comprised of tandem Zn-doped CuInS2 QDs-decorated metal oxide electrodes (BiVO4 and Cu2O) for bias-free solar water splitting. Both the ligands capped on QDs and QDs-electrode heterojunctions are rationally engineered to promote the photo-induced charge transfer in the PEC system, delivering a solar-to-hydrogen efficiency of 0.65% with excellent stability.

Ligand‐Engineered Quantum Dots Decorated Heterojunction Photoelectrodes for Self‐Biased Solar Water Splitting

A cost-effective and high-efficiency photoelectrochemical (PEC) water splitting system based on colloidal quantum dots (QDs) represents a potential solar-to-hydrogen (STH) conversion technology to achieve future carbon neutrality. Herein, a self-biased PEC cell consisting of BiVO4 photoanode and Cu2 O photocathode both decorated with Zn-doped CuInS2 (ZCIS) QDs is successfully fabricated. The intrinsic charge dynamics of the photoelectrodes are efficiently optimized via rational engineering of the surface ligands capped on QDs with controllable chain lengths and binding affinities to the metal oxide electrodes. It is demonstrated that the short-chain monodentate 1-dodecanethiol ligands are beneficial to ZCIS QDs for suppressing charge recombination, which enables the construction of tight heterojunction with coupled metal oxide electrodes, leading to effective photo-induced charge transfer/injection for enhanced PEC performance. The QD decorated BiVO4 and Cu2 O photoelectrodes in pairs demonstrate a self-biased PEC water splitting process, delivering an STH efficiency of 0.65% with excellent stability under AM 1.5 G one-sun illumination. The results highlight the significance of synergistic ligand and heterojunction engineering to build highly efficient and robust QDs-based PEC devices for self-biased solar water splitting.