Photoelectrocatalytic Hydrogen Generation Research Articles

Photoelectrocatalytic Hydrogen Generation: Current Advances in Materials and Operando Characterization.

Photoelectrochemical (PEC) hydrogen generation is a promising technology for green hydrogen production yet faces difficulties in achieving stability and efficiency. The scientific community is pushing toward the development of new electrode materials and a better understanding of the underlying reactions and degradation mechanisms. Advances in photocatalytic materials are being pursued through the development of heterojunctions, tailored crystal nanostructures, doping, and modification of solid-solid and solid-electrolyte interfaces. Operando and in situ techniques are utilized to deconvolute the charge transfer mechanisms and degradation pathways. In this review, both materials development and Operando characterization are covered for advancing PEC technologies. The recent advances made in the PEC materials are first reviewed including the applied improvement strategies for transition metal oxides, nitrites, chalcogenides, Si, and group III-V semiconductor materials. The efficiency, stability, scalability, and electrical conductivity of the aforementioned materials along with the improvement strategies are compared. Next, the Operando characterization methods and cite selected studies applied for PEC electrodes are described. Operando studies are very successful in elucidating the reaction mechanisms, degradation pathways, and charge transfer phenomena in PEC electrodes. Finally, the standing challenges and the potential opportunities are discussed by providing recommendations for designing more efficient and electrochemically stable PEC electrodes.

Solvothermal preparation of hydrangea-like CuBi2O4 twining TiO2 NTAs with enhanced photoelectrocatalytic dye degradation and hydrogen generation

Ternary oxide semiconductor could effectively adjust the energy band gap and location by changing the elemental ratio, which remarkably benefits the electron transfer and photoelectrocatalytic H2 generation. In this paper, hydrangea-like CuBi2O4 sensitizers were prepared on TiO2 nanotube arrays (TiO2 NTAs) by one-pot solvothermal deposition. The alkali kind showed vital influences on the microstructure and photoelectrocatalytic performance of CuBi2O4/TiO2 NTAs, and the excellent pollutant remediation, photoelectric conversion and photoelectrocatalytic water splitting were achieved by the sample prepared by C6H12N4. Under visible light irradiation, the optimized sample displayed the higher photoelectrocatalytic H2 generation rate (87.42 μmol·cm−2·h−1) than that of samples prepared using other alkali kinds. Moreover, the CuBi2O4/TiO2 NTAs also exhibited high organic dye and Cr(VI) removal performance, and the outstanding photoelectrocatalytic activity indicates the novel strategy for the construction of CuBi2O4/TiO2 NTAs photocatalyst for H2 generation by effective photocatalytic water splitting.

Polygonal gold nanocrystal induced efficient phase transition in 2D-MoS2 for enhancing photo-electrocatalytic hydrogen generation

Plasmonic nanocrystals (NCs) assisted phase transition of two-dimensional molybdenum disulfide (2D-MoS2) unlashes numerous opportunities in the fields of energy harvesting via electrocatalysis and photoelectrocatalysis by enhancing electronic conductivity, increasing catalytic active sites, lowering Gibbs free energy for hydrogen adsorption and desorption, etc. Here, we report the synthesis of faceted gold pentagonal bi-pyramidal (Au-PBP) nanocrystals (NC) for efficient plasmon-induced phase transition (from 2 H to 1 T phase) in chemical vapor deposited 2D-MoS2. The as-developed Au-PBP NC with the increased number of corners and edges showed an enhanced multi-modal plasmonic effect under light irradiations. The overpotential of hydrogen evolution reaction (HER) was reduced by 61 mV, whereas the Tafel slope decreased by 23.7 mV/dec on photoexcitation of the Au-PBP@MoS2 hybrid catalyst. The enhanced performance can be attributed to the light-induced 2H to 1 T phase transition of 2D-MoS2, increased active sites, reduced Gibbs free energy, efficient charge separation, change in surface potential, and improved electrical conductivity of 2D-MoS2 film. From density functional theory (DFT) calculations, we obtain a significant change in the electronic properties of 2D-MoS2 (i.e. work function, surface chemical potential, and the density of states), which was primarily due to the plasmonic interactions and exchange-interactions between the Au-PBP nanocrystals and monolayer 2D-MoS2, thereby enhancing the phase transition and improving the surface properties. This work would lay out finding assorted routes to explore more complex nanocrystals-based multipolar plasmonic NC to escalate the HER activity of 2D-MoS2 and other 2D transition metal dichalcogenides.

Photoelectrocatalytic hydrogen generation coupled with reforming of glucose into valuable chemicals using a nanostructured WO3 photoanode

Coupling the photo-oxidation of biomass derived substrates with water splitting in a photoelectrochemical (PEC) cell is a broadly discussed approach intended to enhance efficiency of hydrogen generation at the cathode. Here, we report a PEC device employing a nanostructured semitransparent WO3 photoanode that, irradiated with simulated solar light achieves large photocurrents of 6.5 mA cm−2 through oxidation of glucose, a common carbohydrate available in nature that can be obtained by processing waste biomass. The attained photocurrents are in a large part due to the occurrence of the photocurrent doubling, where oxidation of glucose by the photogenerated positive hole is followed by injection by the formed intermediate of an electron into the conduction band of WO3. Selection of an appropriate supporting electrolyte enabled effective reforming of glucose into valuable products: gluconic and glucaric acids, erythrose and arabinose with up to 64% total Faradaic yield attained at ca 15% glucose conversion.

Sp-Carbon Incorporated Conductive Metal-Organic Framework as Photocathode for Photoelectrochemical Hydrogen Generation.

Metal-organic frameworks (MOFs) have attracted increasing interest for broad applications in catalysis and gas separation due to their high porosity. However, the insulating feature and the limited active sites hindered MOFs as photocathode active materials for application in photoelectrocatalytic hydrogen generation. Herein, we develop a layered conductive two-dimensional conjugated MOF (2D c-MOF) comprising sp-carbon active sites based on arylene-ethynylene macrocycle ligand via CuO4 linking, named as Cu3 HHAE2 . This sp-carbon 2D c-MOF displays apparent semiconducting behavior and broad light absorption till the near-infrared band (1600 nm). Due to the abundant acetylene units, the Cu3 HHAE2 could act as the first case of MOF photocathode for photoelectrochemical (PEC) hydrogen generation and presents a record hydrogen-evolution photocurrent density of ≈260 μA cm-2 at 0 V vs. reversible hydrogen electrode among the structurally-defined cocatalyst-free organic photocathodes.

Ultrathin MoSe2 nanosheet anchored CdS-ZnO functional paper chip as a highly efficient tandem Z-scheme heterojunction photoanode for scalable photoelectrochemical water splitting

Rational design of photoelectrode architectures is deemed as an effective solution to enhance efficiency of photoelectrochemical water splitting for conquering increasingly prominent environmental problems. Herein, a programmable flexible photoanode with built-in tandem Z-scheme configuration fabricated by in-situ growth of MoSe2-CdS-ZnO array with ultrathin nanosheet-interlaced-nanorod structure on the Au paper electrode, is firstly reported. By taking advantages of the interwoven nanonetwork structure, high conductivity as well as larger porosity of the as-fabricated Au paper electrode, a stable light-harvesting paper chip with fast transfer/separate mediators of the charge/carriers is thus integrated. By virtue of double internal electric fields (IEFs) and photothermal effect, the developed MoSe2-CdS-ZnO photoanode exhibits incident-photon-to-current efficiency of 52 % under 460 nm of light irradiation, and the current density reaches 2.4 mA cm−2 at 0.3 V versus normal hydrogen electrode, which is comparable with respect to current state-of-the-art “type-II-scheme”, “surface-scheme”, and cocatalyst-free photocatalysts (0.03–2.4 mA cm−2). Consequently, the paper-based photoanode achieves admirable photoelectrocatalytic hydrogen generation property (39.7 μmol cm−2 h-1). The synergistic effect of tailorable tandem Z-scheme configuration with double IEFs and delineating of 3D cross-linked network structure of the proposed photoanode in this work may open an avenue for constructing high-performance photoelectrochemical water splitting devices.

Promoting the photo-induced charge separation and photoelectrocatalytic hydrogen generation: Z-scheme configuration of WO3 quantum nanodots-decorated immobilized Ti/TiO2 nanorods

The photoelectrocatalytic hydrogen production, especially using 1D TiO2 nanostructures, has been considered as a clean and sustainable approach to cope with energy crisis. Nevertheless, the large band gap energy of TiO2 and the rapid photo-induced charges recombination have limited its practical application. Therefore, in this study, WO3 quantum nanodots were employed with immobilized TiO2 nanorod arrays (TNRs-WQNDs) to tackle these drawbacks. Based on the results, the incorporation of WQNDs ameliorated both the optical and photoelectrochemical properties of TNRs. In this relation, the introduction of WQNDs into TNRs lattice using 10 mg WCL4 (TNRs-WQNDs (10)), as the optimum amount of tungsten precursor, not only made band gap energy much narrower (from 3 to 2.1 eV), but also significantly improved the photocurrent density from 0.92 to 1.67 mA/cm2 (at 1.23 V vs. RHE). In addition, both the STH and photoconversion efficiencies of TNRs-WQNDs (10) were about 1.7 and 1.5 times more than those of pure TNRs, respectively. As a result of these enchantments, the coupling of WQNDs with TNRs was able to increase the photoelectrocatalytic hydrogen production from 1.4 to 2.4 mmol under UV irradiation. An acceptable photoelectrocatalytic performance was further observed under visible light irradiation, where TNRs-WQNDs (10) could generate almost 1.5 mmol of hydrogen. Meanwhile, by investigating the mechanism of photoelectrocatalytic hydrogen production, it was revealed that the reaction pathways over TNRs-WQNDs (10) conformed to the Z-scheme theory. Finally, the fifth incessant cycled test indicated that TNRs-WQNDs (10) photoanode had excellent chemical stability and low photo-corrosion ability.

Three-Dimensional Carbonaceous Aerogels Embedded with Rh-SrTiO3 for Enhanced Hydrogen Evolution Triggered by Efficient Charge Transfer and Light Absorption

Photocatalytic and photoelectrocatalytic hydrogen generation from water splitting by utilizing the visible spectrum of sunlight has been recognized as one of the promising energy conversion applications. Herein, we report the three-dimensional (3D) superstructure of g-C3N4 and reduced graphene oxide embedded with Rh-doped SrTiO3 nanoparticles as ternary aerogels for efficient hydrogen production. The optimized aerogel exhibits high competency for visible light harvesting due to the unique 3D morphology and shows excellent hydrogen evolution performance with quantum efficiencies of 51.1 and 26.9% at 450 and 600 nm monochromatic wavelengths, respectively. The 3D arrangement of integrated components helps in enhanced light absorption due to multiple reflections of incident light within the system and provides a high surface area with abundant reaction sites. Moreover, the ternary heterojunction facilitates efficient charge transfer owing to the suitable band positions of each component as evidenced by fluorescence lifetime, photocurrent, and impedance spectroscopic measurements, resulting in enhanced photocatalytic performance. In addition, the photoelectrocatalytic hydrogen evolution activity reveals the multifunctional nature of the synthesized catalysts. Thus, the hybrid design of the photocatalytic system realizes efficient hydrogen production in suspension and demonstrates the potential of aerogel-based materials as next-generation photocatalysts.

Photocatalytic Hydrogen Generation from pH-Neutral Water by a Flexible Tri-Component Composite

In this work we examine the benefits of using carefully designed tri-component composites to fabricate flexible photocathode electrodes for photo-electrocatalytic hydrogen (H2) generation from neutral pH water. We report H2 production by a tri-component composite thin-film containing CuO nanowires (CuO NW), reduced graphene oxide (rGO) and polypyrrole (PPy). At − 1.1 V vs Ag/AgCl in 0.5 M Na2SO4 (pH 6.8) with a hole-scavenger, under weak light illumination, he photocurrent performance was fivefold greater than the bi-component CuO–rGO control having the same absolute quantities of CuO and rGO. It was 30-fold greater than the CuO–PPy control. The tri-component CuO–rGO–PPy thin film therefore displayed an active H2-generating capacity compare with its bi-component analogues. It, effectively, exploited the advantages of each component, including the suppression of charge recombination afforded by the rGO, and the photocorrosion protection, immobilization and flexibility afforded by the PPy, whilst avoiding their disadvantages. Entry for the Table of contents

Construction of CdSe polymorphic junctions with coherent interface for enhanced photoelectrocatalytic hydrogen generation

CdSe with high densities of coherent polymorphic zincblende/wurtzite (ZB/WZ) interfaces were deposited on TiO2 nanorod arrays (NRAs) by electrodeposition and an optimized annealing process. In situ TEM annealing experiments observed the formation of the ZB/WZ polymorphic junctions that resulted from the change of atomic stacking sequence by dislocation movement induced by stoichiometry changes occurring during annealing. The process deforms CdSe4-tetrahedrons in ZB driving the ZB to WZ phase transition. The formation of ZB/WZ coherent polymorphic junctions enhanced the separation and transport of photo-generated electron-hole pairs in CdSe. The CdSe/TiO2 photoanode produced H2 at a rate of 260.9 μmol cm−2 h-1 under AM 1.5 global sunlight (AM 1.5 G). This is the highest reported value among CdSe-based photoanodes, which indicates the important role of the coherent polymorphic junctions.

Retorting Photocorrosion and Enhanced Charge Carrier Separation at CdSe Nanocapsules by Chemically Synthesized TiO2 Shell for Photocatalytic Hydrogen Fuel Generation

AbstractMetal chalcogenide‐based semiconductor nanostructures are promising candidates for photocatalytic or photoelectrocatalytic hydrogen generation. In order to protect CdSe from photocorrosion, a layer of TiO2 wrapped (shell) onto CdSe (core) nanocapsule via the post‐synthesis process. The morphology studies confirm that a thin crystalline TiO2 shell (3–8 nm) wrapped in all the three directions onto CdSe core and thickness of the shell can be controlled through modulating the titania precursor concentration. The feasibility of pristine CdSe nanocapsules and CdSe@TiO2 in transforming visible light to hydrogen conversion was tested through photocatalysis reaction. The CdSe@TiO2 nanocapsules generated a four‐fold high rate of hydrogen gas (21 mmol.h−1.g−1cat) than pristine CdSe. In order to understand the role of shell@core, we have studied the photoelectrochemical and impedance analysis. The CdSe@TiO2 nanocapsules showed higher photoelectric current generation and lower charge transfer resistance at electrode/electrolyte interfaces compared to pristine CdSe. These studies endorse that chemically synthesized crystalline TiO2 shell played a multifunctional role in (a) surface passivation from photocorrosion, (b) promoting photocharge carrier separation via tunneling process between CdSe and TiO2 interface. As a result, CdSe@TiO2 nanocapsules showed a high conversion efficiency of 12.9 % under visible light irradiation (328 mW.cm−2) and a TOF of 0.05018 s−1.

Enhanced hydrogen generation at designed heterojunctions of Cu2ZnSnS4-rGO-MoS2 through interface engineering

Here, we are reporting interface engineering to create designed heterojunctions in Cu2ZnSnS4-rGO-MoS2 (CZTS-reduced graphene oxide-MoS2), in which abundant high density of nanoscale interfacial contacts are formed. It has been achieved via two-step optimized electrodeposition approach. Further, as-prepared materials have been characterized by microscopic, spectroscopic and electroanalytical techniques. Finally, the concept of generation of designed heterojunctions and synergetic effect were tested for electrocatalytic and photoelectrocatalytic hydrogen generation. The electron-hole pair recombination has been reduced, since the fast transport of photoexcited electrons of CZTS to MoS2 through reduced graphene oxide interfacial contacts. Further, the synergetic effect of increased charge separation between rGO and more catalytically active sites from MoS2 has been attributed to enhanced hydrogen generation.

MoS2/Cu2O nanohybrid as a highly efficient catalyst for the photoelectrocatalytic hydrogen generation

To improve the low photocatalytic efficiency of Cu2O caused by the serious photo-generated electron-hole recombination, in this work, MoS2 is proposed to combine with Cu2O to form a nanohybrid as a photo-electrocatalytic catalyst for hydrogen generation. It is found that the optimized hybrid catalyst of 50M-C exhibits the best performance with a current density of 3700 µA cm−2 at −1.2 V (vs SCE), which is approximately 18-fold and 8-fold higher than those of single MoS2 (200 µA cm−2) and Cu2O (450 µA cm−2), respectively. Moreover, the enhancement mechanism is also discussed, and a synergistic effect between MoS2 and Cu2O is verified, which can reduce the charge transfer resistance and accelerate the separation of photo-generated electrons and holes.

Photoelectrocatalytic Hydrogen Generation Enabled by CdS Passivated ZnCuInSe Quantum Dot-Sensitized TiO₂ Decorated with Ag Nanoparticles.

Here we present the photoelectrocatalytic hydrogen generation properties of CdS passivated ZnCuInSe (ZCISe) quantum dots (QDs) supported by TiO2 nanowires decorated with Ag nanoparticles. In this configuration, Ag nanoparticles were sandwiched between the photo-electrons collector (TiO2) and photo-sensitizers (ZCISe), and acted as an electron relay speeding up the charge carrier transport. ZCISe and CdS enabled the optical absorption of the photoelectrode ranging from ultraviolet to near infrared region, which significantly enhanced the solar-to-chemical energy conversion efficiency. A photocurrent of 10.5 mA/cm2 and a hydrogen production rate of about 52.9 μmol/h were achieved under simulated sunlight (1.5 AG).

CdCl2-assisting heat-treatment: Enhanced photoelectrocatalytic hydrogen generation and stability of CdS/ZnO nanoheterojunction arrays

Hydrogen generation efficiency and stability of the photoelectrocatalytic (PEC) water splitting relate closely to the crystallinity and the interface structure of the photoanodes. Here we demonstrated a feasible strategy for improving the cystallinity and interface quality of the ZnO/CdS nanoheterojunction arrays (NHAs) via CdCl2-assisting post-treatment. CdCl2 treatment was found to promote the recrystallization and densification of the CdS shell layer, the formation of the ZnxCd1-xS intermediate layer between ZnO and CdS, and the creation of an intermediate band (IB) in the forbidden band of CdS due to the high-density ClS states. Meanwhile, the annealing temperature was also lowered from 550 °C to 430 °C with the assistance of CdCl2 treatment. These improvements facilitate the seperation and transport of the photogenerated carriers and extends the light absorption range, resulting in extremely enhanced photocatalytic current and stability. Consequently, the photocatalytic currency reaches to 22 mA cm−2 under the 100 mW cm−2 illumination with the xenon lamp (λ > 420 nm), which is nearly two times larger than that annealed solely at 550 °C but without CdCl2 treatment. The photocatalytic current remains 92% of the initial value after 20-h photocatalytic test.

Microwave-Assisted Greener Synthesis of Defect-Rich Tungsten Oxide Nanowires with Enhanced Photocatalytic and Photoelectrochemical Performance

Exploring semiconductor materials with superior photocatalytic activity is desirable to mitigate the crisis associated with rapid depletion of fossil fuels and environmental pollutions. Herein we report the synthesis of orthorhombic stacked WO3·H2O square nanoplates by mixing WCl6 (0.025 M) in ethanol at room temperature via a precipitation method. On the other hand, hierarchical urchin-like W18O49 nanostructures composed of nanowires were synthesized from the preceding solution within 10 min through a microwave-assisted route. The morphology evolution from nanoplates to nanowires proceeds through a dissolution and recrystallization mechanism, as demonstrated in detail by varying the reaction duration and temperature. The as-synthesized WO3·H2O nanoplates and W18O49 nanowires were employed for the photocatalytic degradation of rhodamine B and photoelectrocatalytic hydrogen generation through water splitting in a neutral medium. Furthermore, the as-synthesized W18O49 nanostructures are employed as electroc...

Fabrication of ternary polyaniline-graphene oxide-TiO2 hybrid films with enhanced activity for photoelectrocatalytic hydrogen production

Abstract In this work, the polyaniline-graphene oxide-TiO 2 (PANI/GO/TiO 2 ) ternary hybrid films have been successfully fabricated on ITO electrodes via self-deposition of TiO 2 , GO and in-situ electropolymerization of aniline in a controllable method. The microstructures, morphologies, and photoelectrochemical properties of the as-prepared PANI/GO/TiO 2 films in different multi-layer structure were characterized and evaluated systematically. The experimental results showed that the additions of GO and PANI endow the films visible-light responsive activity. Then the hybrid films were employed for the first time as photoanode in photoelectrocatalytic (PEC) water reduction for the hydrogen generation. Compared with pristine TiO 2 electrode, the ternary hybrid films with alternative GO, TiO 2 and outer PANI layer presented the best PEC activity, and by which the hydrogen generation rate is higher than most of the reported TiO 2 -based nanophotocatalysts. PEC mechanism analysis suggested that an efficient charge transfer would occur at the interface of PANI and GO/TiO 2 due to the matched band potentials, and PANI served as the roles of both electron collector and transporter, so the collected electrons readily transferred to the counter electrode under a certain bias voltage to reduce water into H 2 . In addition, the results of the contrast experiments demonstrated that the used electrolyte also played an important role in PEC water reduction, and the seawater might be an ideal medium for PEC process. This study is meaningful for the development of other new photoanode materials for PEC hydrogen generation.

An improved carbothermal process for the synthesis of fine-grained boron carbide microparticles and their photoelectrocatalytic activity

Herein we develop an improved carbothermal process using cellulose as organic carbon resources to synthesize uniform B4C particles in fine-grained size. The improvement of the proposed carbothermal processes lies in two points: (i) we use immiscible hexane/water solvents to obtain high-dispersed boric acid (BA), which promotes the esterification of BA with organic carbon; (ii) the boron oxide/carbon resources are ground sufficiently before high-temperature carbonization. The purpose of these two procedures is to increase the homogeneity of precursors, and their effects on the final crystalline structure and morphology of B4C are studied systematically. The results show that uniform fine-grained B4C in about 4µm is successfully fabricated, indicating the homogeneity of precursors can effectively meliorate the B4C powder in a smaller size. The photoelectrochemical and photoelectrocatalytic performances of the as-prepared fine-gained B4C powder are also investigated. Interestingly, the fine B4C microparticles exhibited a good photoelectrocatalytic hydrogen generation activity in water reduction.

(Invited) Enhanced Photoelectrocatalytic Activity for Splitting Water Based on Heterostructured TiO2 Nanotube Arrays

Photoelectrocatalytic water splitting is widely recognized as one of the most promising strategies to large-scale production of hydrogen for renewable energy. To further enhance the photoelectrocatalytic efficiency, severalheterostructures based on TiO2 nanotube arrays were developed in this work. (1) TiO2 nanotube arrays (TNTAs) were decorated with NiO nanoparticles via a sequential chemical bath deposition (CBD) approach to yield NiO@TNTA photoanodes. It demonstrated that the incident-photon-to-current-conversion efficiency (IPCE) and hydrogen production rate of the optimized NiO@TNTA reached 62.8% and 37.8 μmol.h-1.cm-2, respectively, approximately 5.0 times higher than pure TNTAs, which was attributed primarily to the efficient separation of photogenerated charge carriers at the p–n junction of p-type NiO and n-type TiO2. (2) CuxZn1-xIn2S4 ultrathin nanosheets on TiO2 nanotube arrays (CZIS@TNTAs) was successfully synthesized by solvothermal reaction. It found that the CuxZn1-xIn2S4 ultrathin nanosheets on TNTAs significantly enhanced visible light absorption and and a near 8.0-fold increase in photoelectrocatalytic hydrogen production rate was achieved compared to that of the blank TNTAs. The superior photoelectrocatalytic activity of CZIS@TNTAs heterostructured composite electrode was mainly due to enhanced light absorption and separation of photo-generated charges, and facilitating electron transport along the 1D TiO2 structure. (3) TiO2 nanotube arrays (TNTAs) sensitized by palladium quantum dots (Pd QDs) by a modified hydrothermal reaction. When Pd@TNTA nanocomposites were used as both photoanode and cathode in water splitting, the photon-to-current conversion efficiency of nearly 100% atλ=330 nm and a greatly promoted photocatalytic hydrogen production rate of 592 μmol·h−1·cm−2 under 320 mW·cm−2 irradiation were achieved. The synergy between nanotubular structures of TiO2 and uniformly dispersed Pd QDs on TiO2 facilitated the charge transfer from TiO2 nanotubes to Pd QDs and the high activity of Pd QDs catalytic center, thereby leading to high-efficiency photoelectrocatalytic hydrogen generation.

Improved photoelectrocatalytic hydrogen generation through BiVO4 quantum-dots loaded on nano-structured SnO2 and modified with carbon quantum-dots

Bismuth vanadate (BiVO4) has been widely studied as a promising candidate for oxygen evolution in artificial photosynthesis. However, it was seldom used in hydrogen generation because of its low conduction band and high reaction overpotential. Here, we proposed an effective strategy to address these issues by distributing BiVO4 quantum dots onto nanostructured tin oxide (SnO2). The nanostructured SnO2 simultaneously served as the host substrate and a passivation layer. Carbon quantum dots were also used to improve the charge transfer and electrocatalytic properties at the BiVO4-SnO2 interface. As expected, the final composite yields a net photocurrent of 2.2mAcm−2 at 0.6Vvs. Ag/AgCl, and a hydrogen generation rate of 0.54μmol·h−1 without bias. The excellent performance was due to the enhanced electron energy, effective charge separation at the BiVO4-SnO2 interface, and the fast hole transfer from BiVO4 to carbon quantum dots and electrolyte.