Photoelectrocatalytic Hydrogen Production Research Articles

Highly enhanced performance of heterojunction Bi2S3/BiVO4 photoanode for photoelectrocatalytic hydrogen production under solar light irradiation

A heterojunction structure of BiVO4 coupled with a narrow bandgap photocatalyst Bi2S3 was fabricated forming a composite material with strong capacity in visible light absorption and enhancement in the separation rate of photogenerated charge carriers owing to their suitable band structures. As a result, efficiency of hydrogen production through photoelectrocatalysis is highly enhanced. The morphology and composition of as-prepared sample electrodes are measured through X-Ray Diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HR-TEM) and X-ray photoelectron spectroscopy (XPS). The performance of the hybrid nanostructure Bi2S3/BiVO4 photoelectrode was found to be related to the growing process of Bi2S3 nanowire during the hydrothermal preparation process. The composited Bi2S3/BiVO4 photoanode achieved a photoconversion efficiency of 2.9% which is nearly 3-fold that of the bare BiVO4 electrode under visible light irradiation, while the hydrogen production was greatly enhanced by nearly 5-fold in the photoelectrocatalytic hydrogen production reaction.

Enhanced photoelectrocatalytic hydrogen production via Bi/BiVO4 photoanode under visible light irradiation

Photoelectrocatalytic hydrogen production is a clean and sustainable way to combat energy crises and environmental issues. The performance of BiVO4 which acts as a promising photoanode could be effectively enhanced by loading with Bi nanoparticles. In this study, a viable method to fabricate Bi/BiVO4 electrode was proposed to enhance hydrogen production through a photoelectrocatalytic reaction. The results indicated that Bi nanoparticles loaded under optimal condition could obviously increase the photocurrent density of the BiVO4 electrode from 0.9 mA cm−2 to 2.0 mA cm−2 under visible light illumination. Furthermore, the photoelectrochemical hydrogen production efficiency could have a 2.5-fold improvement with the addition of 20 ppm phenol. The possible mechanism of the enhanced performance and the function of phenol in the overall reaction was discussed.

Ultrafine Si nanowires/Sn3O4 nanosheets 3D hierarchical heterostructured array as a photoanode with high-efficient photoelectrocatalytic performance

Constructing a high performance three-dimensional (3D) semiconductor photoelectrode for photoelectrocatalytic hydrogen (H2) production by water splitting is a promising method to resolve the current energy and environmental issues. Here, a ultrafine Si nanowires/Sn3O4 nanosheet (SiNWs/Sn3O4) 3D hierarchical heterostructured photoanode was synthesized via a facile approach with a metal-assisted chemical etching step following an in situ hydrothermal synthesis process. The ultrafine SiNWs/Sn3O4 3D hierarchical heterostructured photoanode exhibits significantly enhanced photoelectrochemical activity, and its photocurrent density is 8 times higher than that of single phase structures of SiNWs. This increase of catalytic activity may be attributed to the enhancement of the full-spectrum light absorption, decrease of the photocarrier recombination rate and a low transmission resistance at the catalyst/electrolyte interface. This work provides a novel design for preparing highly efficient Si based 3D heterostructured catalysts for the production of clean energy.

TiO2 nanotube arrays modified with nanoparticles of platinum group metals (Pt, Pd, Ru): enhancement on photoelectrochemical performance

Highly ordered TiO2 nanotube arrays (TiO2 NTs) were synthesized by anodization method using a titanium foil and further modified with nanoparticles (O = 2~10 nm) of three platinum group metals (that is, platinum, palladium, and ruthenium) through potentiostatic pulsed electrodeposition method to obtain the composite material. Compared with pure TiO2 NTs, all the three composite samples (M-TiO2 NTs, M = Pt, Pd, Ru) showed different enhancement effects on the light responses, as well as different photoelectrochemical performances. In this study, the performance of M-TiO2 NTs, which worked as photoanode and cathode, was investigated. Ru-TiO2 exhibited the best degradation yield (~ 85.8%) when applied as photoanode under visible light illumination, which indicated the platinum group metal could also be induced under visible irradiation, not just served as the co-catalyst. M-TiO2 NTs as cathode were evaluated under the hydrogen evolution reaction (HER). The three M-TiO2 NT electrodes showed an improved efficiency over pure TiO2 NTs, while Pt-TiO2 NTs performed even better (without any sacrificial agent) with higher Faradic efficiency than platinum electrode in the photoelectrocatalytic hydrogen production, which could be explained by the uniform and fine metal nanoparticles on the surface of TiO2 NTs to offer abundant active sites for the reaction.

Donor-Acceptor Supramolecular Organic Nanofibers as Visible-Light Photoelectrocatalysts for Hydrogen Production.

Perylene tetracarboxylic diimide (PTCDI) derivatives have been extensively studied for one-dimensional (1D) self-assembled systems and for applications in photocatalysis. Herein, we constructed a PTCDI-based donor-acceptor (D-A) supramolecular system via in situ self-assembly on an indium tin oxide conductive glass surface. The self-assembled PTCDI nanostructures exhibit well-defined nanofibril morphologies and strong photocurrents. Interestingly, a strong and reversible electrochromic color change was observed during cyclic voltammetry. The color of the nanofibers changed from red to blue and then to violet as the reduction progressed to the radical anion and then to the dianion. This series of one-electron reductions was confirmed by UV absorption, electron paramagnetic resonance spectroscopy, and hydrazine reduction. Most importantly, these PTCDI nanofibers exhibit efficient photoelectrocatalytic hydrogen production with remarkable stability under xenon lamp illumination (λ ≥ 420 nm). Among the three nanofibers prepared, the fibers assembled from PTCDI molecule 2 were found to be the most effective catalyst with 30% Faradaic efficiency. In addition, the nanofibers produced hydrogen at a steady-state for more than 8 h and produced repeatable results in 3 consecutive testing cycles, giving them great potential for practical industrial applications. Under an applied bias voltage, the 1D intermolecular stacking along the long axis of the nanofibers affords efficient separation and migration of photogenerated charge carriers, which play a crucial role in the photoelectrocatalytic process. As a proof-of-concept, the D-A-structured PTCDI nanofibers presented herein may guide future research on photoelectrocatalysis based on self-assembled supramolecular systems by providing more options for material design of the catalysts to achieve greater efficiencies.

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.

The Design of a New Cobalt Sulfide Nanoparticle Implanted Porous Organic Polymer Nanohybrid as a Smart and Durable Water-Splitting Photoelectrocatalyst.

Development of an inexpensive, efficient and robust nanohybrid catalyst as a substitute for platinum in photoelectrocatalytic hydrogen production has been considered intriguing and challenging. In this study, the design and sequential synthesis of a novel cobalt sulfide nanoparticle grafted Porous Organic Polymer nanohybrid (CoSx @POP) is reported and used as an active and durable water-splitting photoelectrocatalyst in the hydrogen evolution reaction (HER). The specific textural and relevant chemical properties of as-synthesised nanohybrid materials (Co3 O4 @POP &CoSx @POP) were investigated by means of XRD, XPS, FTIR, 13 C CP MAS NMR, spectroscopy, HR-TEM, HAADF-STEM with the corresponding elemental mapping, FE-SEM and nitrogen physisorption studies. CoSx @POP has been evaluated as a superior photoelectrocatalyst in HER, achieving a current density of 6.43 mA cm-2 at 0 V versus the reversible hydrogen electrode (RHE) in a 0.5 m Na2 SO4 electrolyte which outperforms its Co3 O4 @POP analogue. It was found that the nanohybrid CoSx @POP catalyst exhibited a substantially enhanced catalytic performance of 1.07 μmol min-1 cm-2 , which is considered to be ca. 10 and 1.94 times higher than that of pristine POP and CoSx , respectively. Remarkable photoelectrocatalytic activity of CoSx @POP compared to Co3 O4 @POP toward H2 evolution could be attributed to intrinsic synergistic effect of CoSx and POP, leading to the formation of a unique CoSx @POP nanoarchitecture with high porosity, which permits easy diffusion of electrolyte and efficient electron transfer from POP to CoSx during hydrogen generation with a tunable bandgap, that straddles between the reduction and oxidation potential of water.

(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.

Double quantum dots decorated 3D graphene flowers for highly efficient photoelectrocatalytic hydrogen production

Photoelectrocatalysis (PEC) has been demonstrated as a promising technique for hydrogen production. However, the high over-potential and high recombination rate of photo-induced electron-hole pairs lead to poor hydrogen production efficiency. In order to overcome these problems, TiO2 and Au dual quantum dots (QDs) on three-dimensional graphene flowers (Au@TiO2@3DGFs) was synthesized by an electro-deposition strategy. The combination of Au and TiO2 modulates the band gap of TiO2, shifts the absorption to visible lights and improves the utilization efficiency of solar light. Simultaneously, the size-quantization TiO2 on 3DGFs not only achieves a larger specific surface area over conventional nanomaterials, but also promotes the separation of the photo-induced electron-hole pairs. Besides, the 3DGFs as a scaffold for QDs can provide more active sites and stable structure. Thus, the newly-developed Au@TiO2@3DGFs composite exhibited an impressive PEC activity and excellent durability. Under −240mV potential (vs. RHE), the photoelectric current density involved visible light illumination (100mWcm−2) reached 90mAcm−2, which was about 3.6 times of the natural current density (without light, only 25mAcm−2). It worth noting that the photoelectric current density did not degrade and even increased to 95mAcm−2 over 90h irradiation, indicating an amazing chemical stability.

Promoted Photoelectrocatalytic Hydrogen Production Performance of TiO2 Nanowire Arrays by Al2O3 Surface Passivation Layer

Promoted Photoelectrocatalytic Hydrogen Production Performance of TiO2 Nanowire Arrays by Al2O3 Surface Passivation Layer

High-efficiency photoelectrochemical hydrogen generation enabled by p-type semiconductor nanoparticle-decorated n-type nanotube arrays

A photoelectrocatalytic hydrogen production rate of 37.8 μmol h−1 cm−2 was obtained by a newly designed NiO nanoparticle modified TiO2 nanotube array photoanode.

Photocurrent increase by metal modification of Fe2O3 photoanodes and its effect on photoelectrocatalytic hydrogen production by degradation of organic substances

The present work reports the investigation of photocurrent increase by metal modification of Fe2O3 photoanodes and its effect on photoelectrocatalytic hydrogen production using aqueous solutions containing various organic compounds. Fe2O3 photoanodes were prepared by the electrodeposition method. The efficiency of various metal modifiers of the hematite structure (Ti, Ni, Sn, Co and Cu) has been tested by monitoring the photoelectrochemical behavior of the ensuing photoanodes. Hydrogen production was monitored in an H-shaped reactor using pure and metal-modified hematite films deposited on FTO electrodes as photocatalyst while a combination of commercial carbon paste with dispersed Pt nanoparticles was used as electrocatalyst. In all cases, hydrogen production was obtained by application of a small external electric bias (in the range 0.5- 0.7V vs Ag/AgCl electrode). Highest photocurrent production has been achieved with a Ti-modified Fe2O3 photoanode in the presence of glucose as sacrificial agent.

Electrodeposited Ti-doped hematite photoanodes and their employment for photoelectrocatalytic hydrogen production in the presence of ethanol

Hematite photoanodes have been constructed and doped with titanium by electrodeposition followed by high temperature annealing. Efficient photoanodes were thus made and optimized and were used for the construction of photoelectrochemical cells employed for hydrogen production both by water splitting in the absence of sacrificial agents and by photo-reforming in the presence of ethanol. The photocurrent substantially increased in the presence of ethanol and it was followed by a large increase in the rate of hydrogen production, which almost doubled in the presence of ethanol. Hydrogen was always produced under electric bias.

Photoelectrocatalytic hydrogen production from oilfield-produced wastewater in a filter-press reactor using TiO2-based photoanodes

Photoelectrocatalytic hydrogen production and simultaneous oxidation of organic pollutants from oilfield-produced wastewater were evaluated in a continuous filter-press reactor at bench scale using TiO2-based photoanodes under visible-light illumination. TiO2 films were prepared on AISI/SAE 304 stainless steel expanded meshes by sol-gel dip-coating. Nickeled AISI/SAE 304 stainless steel expanded meshes were used as cathode. Initially, the experiments were carried out using synthetic produced wastewater with a salinity equivalent to that of oilfield-produced wastewater and containing phenol at the same concentration as the refractory organic pollutants in this effluent. Cathodic and anodic potential ranges were established by micro-electrolysis studies using voltammetric techniques. Appropriate cathode/anode area ratios for different flow rates were estimated by macro-electrolysis studies using chronoamperometric measurements, in order to establish the cell currents required to obtain the adequate electrode potentials. After 2h, the highest hydrogen production rate (12.36μmol/h) was achieved at a flow rate of 0.76L/min applying a cell current of 32.44mA and the lowest hydrogen production rate (5.98μmol/h) was achieved at a flow rate of 2.00L/min applying a cell current of 17.90mA. Using oilfield-produced wastewater, the hydrogen production rate was 9.11μmol/h at the most appropriate operating conditions (0.76L/min, 32.44mA).

Glucose oxidation over ultrathin carbon-coated perovskite modified TiO2 nanotube photonic crystals with high-efficiency electron generation and transfer for photoelectrocatalytic hydrogen production

High-efficiency hydrogen production from photoelectrocatalytic glucose oxidation over C@Cr-SrTiO3/TiO2 NTPC with fast electron generation and transfer is demonstrated.

Experimental study of a hybrid photo-electrocatalytic hydrogen production reactor

The current study presents an experimental investigation of a hybrid photo-electrocatalytic hydrogen production reactor for aiming to replace the electrolysis component of the Cu–Cl cycle. The glass material is used to manufacture the lab scale device, consisting of the anolyte and the catholyte compartments separated by the membrane. In the anolyte compartment, a solution of CuCl, HCl and water is used, whereas, in the catholyte compartment, a solution of ZnS, NaOH, Na2S, and water is used. In the present study, ZnS is used as the photocatalyst to generate an additional potential in the catholyte compartment to produce hydrogen by breaking water molecules. Multiple operating parameters, such as applied voltage, solar light intensity, the mass of CuCl and mass of ZnS are varied to observe their effects on the hydrogen production rate. The results obtained from this study show that the rate of hydrogen production varies from 0.73 to 1.61 μg/s with an increase in applied voltage and mass of CuCl from 2.5 to 3.5 V and 5–10 g, respectively. It is also observed that the rate of hydrogen production varies from 1.37 to 1.64 μg/s with an increase in applied voltage and mass of ZnS from 2.5 to 3.5 V and 2–4 g, respectively.

Photoelectrocatalytic hydrogen production by water splitting using BiVO4 photoanodes

Nanocrystalline bismuth vanadate was deposited by simple wet chemistry procedure on FTO electrodes in order to construct visible light responsive photoanodes, which were employed for photoelectrochemical hydrogen production by water splitting. The specific surface area of the films was controlled by the presence of a surfactant template (Triton X-100). It was, however, found that when the quantity of surfactant was relatively high, the stoichiometry of the photocatalyst as well as its activity was lost. The obtained materials were characterized by SEM, XRD, AFM, BET and UV–Vis spectroscopy. Optimized photoanodes were employed in photoelectrochemical cells for water splitting and hydrogen production under electric and chemical bias. Maximum hydrogen production rate was 0.15mmol/h under electric bias of 1.4V vs Ag/AgCl plus 0.37V chemical bias.

Enhanced photoelectrocatalytic hydrogen production activity of SrTiO3–TiO2 hetero-nanoparticle modified TiO2 nanotube arrays

SrTiO3–TiO2 hetero-nanoparticle modified TiO2 nanotube arrays (ST–TiO2 NTAs) were constructed by following these steps: firstly, highly ordered TiO2 nanotube arrays (TiO2 NTAs) were synthesized directly on Ti foils through electrochemical oxidation, then SrTiO3–TiO2 nanoparticles were deposited on the TiO2 NTAs using two-step hydrothermal treatment. SrTiO3–TiO2 nanotube arrays (S–TiO2 NTAs) were also prepared by directly hydrothermal treatment of TiO2 NTAs for comparison. The photoelectrocatalytic hydrogen production activities of all the samples were evaluated by using ethylene glycol as a sacrificial reagent in water under a 300 W xenon arc lamp. The photoelectrocatalytic hydrogen production rate of TiO2 NTAs can be significantly improved by modifying SrTiO3–TiO2 hetero-nanoparticles and achieved a greatly promoted value of 314.9 μmol cm−2 h−1 which was 2.1 times higher than that of the unmodified TiO2 NTAs. Compared to S–TiO2 NTAs, ST–TiO2 NTAs showed a 32.8% increase in hydrogen production rate. Furthermore, SrTiO3–TiO2 hetero-nanoparticle modified TiO2 nanotube arrays exhibited excellent stability and was facile to be safely reused. The improvement of photocatalytic hydrogen production efficiency is attributed to the difference of the conduction band potential between TiO2 and SrTiO3 in SrTiO3–TiO2 hetero-nanoparticles, thereby boosting the transfer and separation of the photogenerated electron–hole pairs.

Photoelectrocatalytic Glucose Oxidation to Promote Hydrogen Production over Periodically Ordered TiO2 Nanotube Arrays Assembled of Pd Quantum Dots

The development of highly efficient and low-cost approaches for catalytic hydrogen production from renewable energy is of tremendous importance for a truly sustainable hydrogen-based energy carrier in future life. Herein, the probability of utilizing solar light to product hydrogen from biomass derivative, glucose, was systematically demonstrated by using the periodically ordered TiO2 nanotube arrays (TNTAs) assembled of Palladium quantum dots (Pd QDs), i.e. Pd QDs@ TNTAs as photoanode. The results showed that remarkably increased photocurrent density was obtained in the glucose solution compared to the pure KOH electrolyte over as-prepared photoelectrode, which indicated that the glucose could be faster oxidized than water oxidation, and thus could promote the hydrogen production on Pt cathode. The yield of hydrogen production from glucose oxidation reached as high as 164.8μmolcm−1 over Pd QDs@TNTAs photoanode and Pt cathode system (denoted as Pd QDs@TNTAs/Pt) under the solar light irradiation for 6h, which was about 15 times higher than that from pure water splitting. The superior hydrogen production performance could be attributed to the less endergonic process of the glucose oxidation than water, as well as the efficient synergistic photoelectrocatalytic (PEC) glucose oxidation over Pd QDs@TNTAs photoanode which possesses excellent photoelectrochemical performance and structure characteristics. Moreover, a probable mechanism for the PEC hydrogen production from biomass derivatives oxidation was proposed and discussed.

Photoelectrocatalytic hydrogen production using nitrogen containing water soluble wastes

Hydrogen has been produced by photoelectrocatalytic degradation of model nitrogen-containing water soluble wastes urea, formamide and aqueous ammonia. Hydrogen production was monitored in a simple reactor using a “Photoelectrocatalytic Leaf” as functional component, i.e. an FTO electrode bearing both photocatalyst and electrocatalyst, which allows for a very simple but effective configuration. Nanoparticulate titania was used as photocatalyst while a combination of commercial carbon paste with dispersed Pt nanoparticles was used as electrocatalyst. Urea produced the largest quantity of hydrogen, which could be accelerated by application of an external electric bias. Current-voltage measurements provided an indication of current-doubling in the case of formamide.