Efficient Photocatalytic Water Splitting Research Articles

Noble-metal-free chalcogenide nanotwins for efficient and stable photocatalytic pure water splitting by surface phosphorization and cocatalyst modification

Chalcogenide photocatalysts are considered excellent candidates for photocatalytic water splitting because of their narrow bandgaps enabling utilization of visible light. However, severe self-oxidation of sulfide ions during water oxidation greatly restricts their application toward pure water splitting. Herein, we report the synthesis of a near-surface P-doped Cd0.5Zn0.5S (CZS) nanotwin photocatalyst, co-modified by red phosphorus (RP) and transition metal phosphides (TMPs, including FeP, Ni2P, and Co2P) by a one-step phosphorization method that enables efficient and stable pure water splitting. We demonstrate that homogenous phosphorus bridges formed from CZS to both RP and TMP because of near-surface P doping. These unique bridges enable effective charge transfer from RP to CZS and then to TMP via a two-electron Z-scheme mechanism. Significantly, the RP for photogenerated holes capture shows great corrosion–resistance during water oxidation, with simultaneous production of H2O2, while TMP promotes H2 evolution. The optimal CZS-P-Co2P shows a H2 evolution rate of 801.3 μmol/h/g for visible-light-driven pure water splitting, with an apparent quantum of 7.46% at 400 nm, which are among the highest reported values over chalcogenide photocatalysts. This work demonstrates the promising application potential of chalcogenides as photocatalysts for pure water splitting.

Piezo-Photocatalytic Synergy in BiFeO3 @COF Z-Scheme Heterostructures for High-Efficiency Overall Water Splitting.

Solar-driven overall water splitting is an ideal way to generate renewable energy while still challenging. For the first time, this work combined covalent organic frameworks (COFs) and piezoelectric material by covalent linkages to form Z-scheme core@shell heterostructure for overall water splitting. Benefiting from the synergistic effect between the polarized electric field and photo-generated charges, as well as the precise adjustment of shell thickness, the carrier separation and utilization efficiency is greatly improved. The optimal BiFeO3 @TpPa-1-COF photocatalyst revealed hydrogen (H2 ) and oxygen (O2 ) production rates of 1416.4 and 708.2 μmol h-1 g-1 under the excitation of ultrasonication coupled with light irradiation, which is the best performance among various piezo- and COF-based photocatalysts. This provides a new sight for the practical application of highly efficient photocatalytic overall water splitting.

Piezo‐Photocatalytic Synergy in BiFeO3@COF Z‐Scheme Heterostructures for High‐Efficiency Overall Water Splitting

AbstractSolar‐driven overall water splitting is an ideal way to generate renewable energy while still challenging. For the first time, this work combined covalent organic frameworks (COFs) and piezoelectric material by covalent linkages to form Z‐scheme core@shell heterostructure for overall water splitting. Benefiting from the synergistic effect between the polarized electric field and photo‐generated charges, as well as the precise adjustment of shell thickness, the carrier separation and utilization efficiency is greatly improved. The optimal BiFeO3@TpPa‐1‐COF photocatalyst revealed hydrogen (H2) and oxygen (O2) production rates of 1416.4 and 708.2 μmol h−1 g−1 under the excitation of ultrasonication coupled with light irradiation, which is the best performance among various piezo‐ and COF‐based photocatalysts. This provides a new sight for the practical application of highly efficient photocatalytic overall water splitting.

Fabrication of 0D/1D/2D ZnS–CuS nanodots/GNRs/g-C3N4 heterojunction photocatalyst for efficient photocatalytic overall water splitting

Photocatalytic water splitting has become a significant challenge in modern chemistry. In this process, the rate-determining step is the hydrogen evolution reaction (HER). In the present work, a surface modification approach for graphitic carbon nitride (g-C3N4) was applied to improve its photocatalytic HER. 0D ZnS–CuS nanodots were synthesized with the hydrothermal method as a co-catalyst to enhance the capability and stability of water splitting in the presence of visible light irradiation. Also, graphene nanoribbons were synthesized from CNTs unzipping to reduce the energy barrier of HER, improve the HE kinetic, and enhance the catalytic performance of the g-C3N4. By using ZnS–CuS/GNRs(2)/g-C3N4 photocatalyst, a low onset potential of 130 mV, slight Tafel slope of 41 mV dec−1, as well as excellent stability of 2000 s was obtained in acidic media. This efficient performance is attributed to the increased visible light absorption level in the proposed photocatalyst and the high stability in electron-hole pairs.

Conduction band tuning by strengthening s-p hybridization of novel layered oxyhalide Bi4SbO8Cl for efficient visible-light photocatalytic water splitting

Bismuth-based Sillen–Aurivillius oxyhalide Bi4MO8Cl are promising visible-light photocatalysts. The element M of [MO4]3- perovskite layer in the Bi4MO8Cl is always a transition element. Due to d orbitals in transition element weakening the Bi 6s and O 2p orbitals hybridization, the bandgap energy would be decreased and the CBM would be lowered. Thus, Bi4MO8Cl always shows feeble reducibility for photocatalytic hydrogen generation. In this paper, we choose the main group element Sb substitute for transition element M in the Sillen–Aurivillius Bi4MO8Cl. Due to the s-p-d hybridization in Bi4NbO8Cl being replaced by only s-p hybridization in Bi4SbO8Cl, the strengthened Bi 6s and O 2p orbitals hybridization would eventually lead to the enlarged energy bandgap and elevated CBM. The bandgap of Bi4SbO8Cl was about 2.53 eV with the CBM estimated about −0.33 eV. Because of the high carrier mobility and strong reducibility brought by the dispersed Bi 6s states in the whole unoccupied states and the raised position of Bi 6p states in the CBM and linearity Sb–O–Sb, Bi4SbO8Cl shows enhanced photocatalytic H2 generation compared to Bi4NbO8Cl under the visible-light irradiation.

ZnInGaS4 heterojunction with sulfide vacancies for efficient solar-light photocatalytic water splitting and Cr(VI) reduction

ZnInGaS4 heterojunction with S vacancies was prepared via the microwave hydrothermal route to boost the solar-light photocatalytic activity for water splitting and Cr (VI) reduction. The tight interface between ZnIn2S4 and ZnGa2S4 favors the rapid separation and transfer of photo-induced electron-hole pairs, and the narrowed band gap is suitable for visible-light harvesting. In addition, S vacancies serve as the adsorption sites and photons capture, leading to the efficient solar utilization. Compared with ZnIn2S4 (0.94 mmol g-1h−1) and ZnGa2S4 (0.33 mmol g-1h−1), the optimal ZnInGaS4 with a In/Ga molar ratio of 1:1 exhibits the better H2 evolution rate (4.47 mmol g-1h−1) and the apparent quantum yield of 20.16 % at wavelength of 400 nm. The removal efficiency of ZnInGaS4 for solar-light driven Cr (VI) reduction is 99.46 % within 140 min, which is higher than ZnIn2S4 (93.14 %) and ZnGa2S4 (89.31 %). The photo-corrosion induces to the deactivation of ZnGa2S4 for solar-light driven H2 evolution and Cr (VI) reduction after five cycles.

Constructing 0D/1D/2D Z-scheme heterojunctions of Ag nanodots/SiC nanofibers/g-C3N4 nanosheets for efficient photocatalytic water splitting

Efficiently constructing nanostructured Z-scheme heterojunctions with good interface contact is a desired route to optimize the photocatalytic property of the materials. In this work, novel 0D/1D/2D Z-scheme silver/silicon carbide/graphitic carbon nitride (Ag/SiC/CN) photocatalysts were prepared from Ag nanodots loaded on SiC nanofibers/CN nanosheets (SiC/CN) composite, using the calcination and chemical reduction routes. The Ag/SiC/CN composite with an optimal 3% Ag loading dose performs the best H2 evolution rate of 2971 μmol g−1 h−1, which is approximately 8.8, 1.5 and 4.5 times compared to CN, SiC/CN and 3% Ag/CN, respectively. Besides the Ag/SiC/CN composite presents a high apparent quantum efficiency (7.3%) and outstanding photo-corrosion resistance stability. The Ag nanodots are served as efficient carriers transfer center and cocatalyst to construct Z-scheme heterojunction interface, which can help to generate more photo-generated carries, shorten the electron transmission distance and increase the electron transfer rate, certifying that 0D/1D/2D Z-scheme photocatalytic system is high-efficiency and has great advantages in photocatalytic applications.

Ferroelectric polarization enabled spatially selective adsorption of redox mediators to promote Z-scheme photocatalytic overall water splitting

<h2>Summary</h2> Although the artificial Z-scheme system, mimicking natural photosynthesis, has shown promising applications in photocatalytic water splitting, it often suffers from the side reaction of redox mediator, which considerably undermines the efficacy of photocarrier utilizations. Herein, we propose to suppress the side reaction by using ferroelectric polarization, which not only provides a strong driving force to spatially separate photocarriers to the oppositely poled surface but also induces spatially selective adsorption of redox ions. Single-domain ferroelectric PbTiO₃ nanoplates have been adopted as a model ferroelectric to construct the Z-scheme system with BiVO₄ particles and a cationic redox mediator. In contrast to the inactive multi-domain ferroelectric PbTiO₃-based system, the so-formed Z-scheme system delivers stable high activity for photocatalytic overall water splitting under both visible light and simulated solar insolation. This work offers a proof of concept to realize efficient solar photocatalytic water splitting based on single-domain ferroelectric Z-scheme system.

TiO2/SiO2 dopant-free nanophotocatalysts for highly efficient photocatalytic water splitting: Challenging traditional TiO2-based systems

Three preparation methods of mesoporous silica nanosupports were investigated for H2 production: molecular imprinting, surface functionalization, and hybrid framework. The effect of the surface nature of SiO2 on the growth and distribution of TiO2 actives sites, as well as on photocatalytic reactions, was also explored. TiO2 and TiCl4 were used as precursors for the catalytic centers, and the results were compared to each other. The molecular imprinting created on the SiO2 support improved the exposure of catalytic species and changed the electronic properties, resulting in a narrow energy bandgap (Eg, 2.85-2.94 eV). A deep discussion of the textural, morphological, optical, spectral, electronic, surface fractal, and crystal structure characteristics of the TiO2/SiO2 metal-free nanocatalyst performance for water splitting is presented. The dopant-free nanocatalysts stand out for the small amount of TiO2 (0.0778–0.1747% wt. Ti/SiO2) used in their preparation and for their high catalytic activity for H2 photoproduction. A surprising performance was achieved by the SiTi1200 sample, 140.22 mmol H2.g−1, mainly due to the specific surface area, the surface fractal structure, and the band gap energy. This performance was much higher than that of commercial P25 and other TiO2 materials, which are more complex catalytic systems reported in the literature. The study shows that easily synthesized TiO2/SiO2 nanosystems with tunable main characteristics may overcome the existing limitations for water splitting by TiO2-based photocatalysts, allowing new opportunities for other catalytic applications.

In situ synthesis of Cu‐doped ZIF‐8 for efficient photocatalytic water splitting

Metal–organic frameworks (MOFs) reached a new level of research in photocatalysis by their virtue of tunable structure, modifiable pores, and a large surface area. Herein, we employed a simple metal ion exchange method to change ZIF‐8 from UV light to visible light absorption photocatalyst. In this work, Cu2+ ions are integrated within the ZIF‐8 framework to synthesize Cu‐doped ZIF‐8 photocatalysts and well characterized by using both the spectroscopic and electrochemical studies. The Cu@ZIF‐8 (CDZ‐20) photocatalyst shows enhanced light‐harvesting ability and remarkable hydrogen generation rate of 13.9 mmolg−1 h−1 with an apparent quantum efficiency (AQE) of 9.08%, which is 17 times higher than that of pristine ZIF‐8 photocatalyst. The higher photocurrent density of 34 μA/cm2 in CDZ‐20 further reinforced the superiority over the ZIF‐8 (1 μA/cm2). This work paves the way to engineer robust copper doped ZIFs photocatalyst under mild synthesis approach for efficient H2 evolution.

Development of Double Perovskite Oxide Photocatalysts for Efficient Visible-Light Driven Photocatalytic Water Splitting and CO2 Reduction

Energy and environment are the key global challenges in the 21st century. Solar energy is considered the most promising clean and sustainable energy resource due to its university, inexhaustible and environmental friendliness. One of the most viable means of solar energy conversion and utilization is artificially converting solar energy into chemical energy as natural photosynthesis does. H2 produced from water splitting and CO2 reduction, are the major research topics of artificial photosynthesis. However, the effective conversion of solar energy into chemical energy by cost-effective artificial means on a large scale remains elusive. Metal oxide-based photocatalysts are the most studied materials for photocatalytic water splitting and CO2 reduction. Particularly, perovskite oxides with the chemical formula of ABO3 have been intensively studied as semiconductor photocatalysts. However, overwhelmingly of the perovskite oxides are only active under UV-light-irradiation, which limited their potential in solar energy application. Therefore, breakthrough technology and step-change materials, particularly, visible-light-responsive photocatalysts are highly desirable for the development of photocatalytic systems. In recent years, copious progress has been made in designing materials that function under visible-light-irradiation. So far, the most successful strategy is anion doping of oxide semiconductors, such as nitrogen or sulfur dope to form oxynitrides and oxysulfides, respectively. For example, nitrogen-doped oxynitrides such as (Ga1-xZnx)(N1-xOx) and ANbO2N (A=Sr, Ba, and La)1, and sulfur-doped oxysulfides such as Sm2Ti2S2O5 2 showed efficient photocatalytic overall water splitting activities under visible-light-irradiation. Particularly, oxynitrides (Ga1-xZnx)(N1-xOx) based photocatalyst sheet, showed remarkable photocatalytic overall water splitting activity with AQE of more than 30% at l»420 nm3. However, these oxynitrides and oxysulfides suffer stability problems due to photocorrosion, hindering their potential practical application in photocatalytic applications. Recently, it has been theorized that double perovskite oxides (DPOs) with the chemical formula of A2BʹB"O6 can function as efficient and stable visible-light-responsive photocatalysts for photocatalytic water splitting and CO2 reduction. However, DPOs have been rarely studied for photocatalytic water splitting and CO2 reduction due to the difficulty of obtaining pure phase materials and the paucity of exposed active sites. Thus, developing efficient and stable visible-light-responsive DPOs photocatalysts for photocatalytic water splitting and CO2 reduction becomes important. In this regard, recently, we have demonstrated a series of efficient and stable visible-light-responsive DPOs photocatalysts for photocatalytic water splitting. For instance, Sr2CoWO6 and Sr2CoTaO6 can serve as an efficient and stable bifunctional photocatalyst for both photocatalytic oxygen evolution reaction (OER) and hydrogen evolution reaction(HER)4, 5, and Sr2NiWO6 can efficiently drive the photocatalytic OER6. Even though these DPOs have been demonstrated as visible-light-responsive photocatalysts with suitable CB and VB positions that straddle the theoretical potentials for overall water splitting, however, one-step overall water splitting has not been achieved so far, and their potential for photocatalytic CO2 reduction has not been studied yet. Overall water splitting under visible-light-irradiation based on particulate photocatalysts is a challenging reaction, which is regarded as one of the “Holy Grail” of sciences. And oxide semiconductors showing both photocatalytic OER and HER activities are rare. Nevertheless, bifunctional photocatalytic OER and HER were successfully demonstrated based on Sr2CoWO6 and Sr2CoTaO6. Further improvement of the material designs and developing appropriate cocatalysts may play a key role in achieving one-step overall water splitting under visible-light-irradiation based on DPOs photocatalysts. This work is mainly to explore the possibility of utilizing DPOs materials as visible-light-responsive photocatalysts for photocatalytic water splitting and CO2 reduction reaction, which is challenging work but has great potential value in advancing science and technology in photocatalysis. We anticipated that this work will provide a novel and rational strategy for improving the light absorption, charge separation and charge utilization in DPOs photocatalysts. References Maeda, K.; Teramura, K.; Masuda, H.; Takata, T.; Saito, N.; Inoue, Y.; Domen, K. The Journal of Physical Chemistry B 2006, 110 (26), 13107-13112.Ma, G.; Kuang, Y.; Murthy, D. H.; Hisatomi, T.; Seo, J.; Chen, S.; Matsuzaki, H.; Suzuki, Y.; Katayama, M.; Minegishi, T. The Journal of Physical Chemistry C 2018, 122 (25), 13492-13499.Kato, H.; Asakura, K.; Kudo, A. Journal of the American Chemical Society 2003, 125 (10), 3082-3089.Idris, A. M.; Liu, T.; Shah, J. H.; Zhang, X.; Ma, C.; Malik, A. S.; Jin, A. Solar RRL 2020, 4 (3), 1900456.Idris, A. M.; Liu, T.; Hussain Shah, J.; Han, H.; Li, C. ACS Sustainable Chemistry&Engineering 2020, 8 (37), 14190-14197.Idris, A. M.; Liu, T.; Hussain Shah, J.; Malik, A. S.; Zhao, D.; Han, H.; Li, C. ACS Applied Materials&Interfaces 2020, 12 (23), 25938-25948.

(Invited) Bulk Heterojunction Organic Semiconductor Photoelectrodes and Photocatalysts for Solar-Driven Water Splitting

The bulk heterojunction (BHJ) concept, which has been successfully developed for organic semiconductor-based photovoltaic devices, offers a promising route to high-performance and inexpensive photocatalyst nanoparticles for solar hydrogen production. However, the suitability organic semiconductors (OSs) towards robust and high efficiency photocatalytic water splitting remains an open question. Herein, efforts to understand the stability of OS-based BHJ photoelectrodes for both solar driven water reduction [1] and oxidation [2] are discussed. The integration of a BHJ photoanode and photocathode into a bias-free solar-driven water splitting device is also reported. Finally, the important aspects needed for translating these systems into nanoparticle photocatalysts are examined. ______________

G‐C3N4/SnS2 van der Waals Heterostructures Enabling High‐Efficiency Photocatalytic Hydrogen Evolution

AbstractVan der Waals (vdW) heterojunction has played an essential role in effectively utilizing solar energy for sustainable hydrogen production. Herein, a 2D/2D g‐C3N4/SnS2 photocatalyst with vdW heterojunction is developed by self‐assembly contacting SnS2 hexagonal nanoplates and g‐C3N4 nanosheets. A reasonable Type‐II charge transfer mechanism based on the vdW heterostructure is proposed and verified by hydroxyl radical generation test. Photocatalysts with vdW heterostructure enable high‐efficiency H2 production under the visible light illumination, of which the optimized rate is about seven times higher than that of SnS2. Experimental analysis and corresponding density functional theory simulation jointly identify that enhanced photocatalytic activity is ascribed to the optimized behavior of photogenerated carriers and promotional interaction between reactants with catalysts. Specifically, charge redistribution and staggered band structure of the heterojunction intrinsically facilitate the efficient interfacial charge migration and separation. Diminished free energy of surface hydrogen adsorption reveals the easier hydrogen adsorption‐desorption for a composite system from the viewpoint of thermodynamics. This work may be attractive for the implementation of rationally synthesizing catalysts for efficient photocatalytic water splitting.

Z-scheme P-doped-g-C3N4/Fe2P/red-P ternary composite enables efficient two-electron photocatalytic pure water splitting

Charge transfer in a semiconductor is crucial for photocatalytic pure water splitting. Herein, we construct a series of P-doped-g-C3N4/Fe2P/red-P (PCN/Fe2P/RP) ternary composite by in-situ phosphorization of a Fe2O3@C/g-C3N4 heterojunction. The as-prepared composite show substantially improved photocatalytic activity toward pure water splitting under visible light irradiation without adding any noble metal. The optimized composite containing 15 wt% Fe2P presents the best activity, with the H2 production rate of 429 µmol g−1 h−1, which is 107 and 39 times higher than that of pristine g-C3N4 and P doped g-C3N4 (PCN), respectively. This noble-metal-free photocatalyst presents a solar-to-hydrogen conversion efficiency of about 0.2% for pure water splitting. It is found that water splitting proceeds via a two-electron pathway with simultaneous production of H2 and H2O2. The improvement relies on the formation of intermediate Fe2P for rapid Z-scheme electron transfer from the midgap state of PCN to the valence band of RP. This work provides a versatile method for fabricating noble-metal-free photocatalyst with controlled charge transfer behavior for efficient photocatalytic pure water splitting.

Ag nanoparticles anchored organic/inorganic Z-scheme 3DOMM-TiO2–x-based heterojunction for efficient photocatalytic and photoelectrochemical water splitting

Narrow spectral response, low charge separation efficiency and slow water oxidation kinetics of TiO 2 limit its application in photoelectrochemical and photocatalytic water splitting. Herein, a promising organic/inorganic composite catalyst Ag/PANI/3DOMM-TiO 2– x with a three-dimensional ordered macro-and meso-porous (3DOMM) structure, oxygen vacancy and Ti 3+ defects, heterojunction formation and noble metal Ag was designed based on the Z-scheme mechanism and successfully prepared. The Ag/PANI/3DOMM-TiO 2– x ternary catalyst exhibited enhanced hydrogen production activity in both photocatalytic and photoelectrochemical water splitting. The photocatalytic hydrogen production rate is 420.90 μmol g –1 h –1 , which are 19.80 times and 2.06 times higher than the commercial P25 and 3DOMM-TiO 2 , respectively. In the photoelectrochemical tests, the Ag/PANI/3DOMM-TiO 2– x photoelectrode shows enhanced separation and transfer of carriers with a high current density of 1.55 mA cm –2 at equilibrium potential of 1.23 V under simulated AM 1.5 G illumination, which is approximately 5 times greater than the 3DOMM-TiO 2 . The present work has demonstrated the promising potential of organic/inorganic Z-scheme photocatalyst in driving water splitting for hydrogen production. A promising organic/inorganic composite catalyst Ag/PANI/3DOMM-TiO 2– x was designed for both photocatalytic and photoelectrochemical water splitting hydrogen production. The activity was improved through the three-dimensional ordered macro- and meso-porous structure, formation of Z-scheme heterojunction, introduce of Ti 3+ defects and oxygen vacancies as well as the SPR effect of noble metal Ag NPs.

Assembly-synthesis of puff pastry-like g-C3N4/CdS heterostructure as S-junctions for efficient photocatalytic water splitting

• A self-assembly strategy was employed to construct puff pastry-like h-CN/CdS heterojunction. • Molecular tailoring of g-C 3 N 4 generated hydrolyzed sol as quasi-homogeneous precursor. • As-assembled architecture exhibited 3.5-fold increased activity for hydrogen evolution. • Strong interfacial interactions contributed to the S-scheme charge transfer in reassembles. Designing S-scheme heterojunctions with strong interfacial interaction is an effective way to facilitate the separation of photocarriers, as well as retaining the strong photoredox abilities. Graphitic carbon nitride (g-C 3 N 4 ) has emerged as a promising material for heterostructure design, but the interfacial hybridization was restricted by the low surface area and limited active sites of bulk g-C 3 N 4 . In this paper, a molecular assembly strategy was employed to synthesize puff pastry-like g-C 3 N 4 /CdS nanoarchitectures with strongly coupled interfaces. The hydrogen bond-mediated reassembly of hydrolyzed g-C 3 N 4 molecules was employed to intercalate ultrafine CdS nanoparticles into 2D g-C 3 N 4 assemblies. The intimate contact between g-C 3 N 4 supports and inlaid CdS contributed to the formation of built-in electric field, which was favorable for the S-scheme separation of photogenerated carriers. As a consequence, the puff pastry-like g-C 3 N 4 /CdS heterojunction exhibited a H 2 evolution rate of 3.37 mmol·g −1 ·h −1 . The strategy used here paves a new avenue toward the assembly synthesis of high-performance S-scheme photocatalysts via molecular tailoring.

Manipulating a TiO2-graphene-Ta3N5 heterojunction for efficient Z-scheme photocatalytic pure water splitting

Titanium dioxide (TiO2)-based photocatalysts are a class of hottest materials in solar water splitting, while limited achievements have been gained to date due to its broad band-gap only responding in UV region and sluggish charge transfer. Here, we reported a ternary TiO2-graphene-Ta3N5 hybrid photocatalyst synthesized via an ultrasonic-hydrothermal method. Compared with pristine TiO2 and Ta3N5, the prepared TiO2-graphene-Ta3N5 present remarkably enhanced photocatalytic pure water splitting behavior with an optimal H2-evolution rate of 180 μmol h−1 g−1. In conjunction with systematic characterizations, we demonstrated the boosted photocatalytic performance is ascribed to both improved visible light utilization and charge transfer behavior. Particularly, it is found that water splitting is achieved through a Z-scheme mechanism, in which the two-dimensional lamellar graphene served as a bridge accelerating the electron transfer from TiO2 to Ta3N5. This work opens avenues to design efficient TiO2-based photocatalyst by embedding conducting layer for rapid electron transfer during solar-fuel conversion.

Non-noble copper ion anchored on NH2-MIL-101(Fe) as a novel cocatalyst with transient metal centers for efficient photocatalytic water splitting

The earth-abundant copper species anchored on the -NH2 of NH2-MIL-101(Fe) as noble-metal-free cocatalysts via transient CuII/CuI centers were obtained via a convenient synthesis technique to achieve excellent photocatalytic hydrogen evolution performance in the dye sensitization system. The prepared sample 6Cu-NM-101 exhibited the best hydrogen evolution activity of 5770.96 μmol·g−1·h−1, which was 4.06 times higher than the original NH2-MIL-101(Fe). A series of characterization tests, especially the CV and the Auger Cu LMM, demonstrated that the transient CuII/CuI center played a significant part in the novel ligand to linker metal charge transfer (LLMCT) process. In other words, the electrons could transfer from the lowest unoccupied molecular orbital (LUMO) energy level of the excited state Eosin Y (EY*) to the transient CuII/CuI center to further accelerate the carrier transfer and separation rate. Our work provided a more convenient and effective strategy to prepare various earth-abundant metal ions based on MOFs as low-cost cocatalysts via transient metal centers to boost the photocatalytic hydrogen evolution performance.

CdS@Mg(OH)2 core/shell composite photocatalyst for efficient visible-light photocatalytic overall water splitting

Coating a protective agent or promoter on the surface of the photocatalyst is a proven good strategy to realize photocatalytic hydrogen production from pure water, but remains still a considerable challenge. Herein, a novel [email protected](OH)2 core/shell composite nanorods photocatalyst was synthesized by coating Mg(OH)2 on CdS surface by hydrothermal and precipitation processes. The coated-Mg(OH)2 layer did not change the structure of CdS, and the photocatalytic overall water splitting performance of the [email protected](OH)2 under visible light irradiation was improved obviously. After loading nano-Pt via the photodeposited method, the hydrogen production rate and stability of Pt/[email protected](OH)2 were 3.3 and 2.4 times that of the Pt/CdS under the visible light irradiation, respectively. The surface Mg(OH)2 layer improved the hydrophilicity and stability of the core/shell composites and increased the amount of active sites, thus improving the photocatalytic properties. It is believed that Mg(OH)2 can be used as a new co-catalyst to enhance the performance of photocatalytic overall water splitting.

In situ growth of crystalline carbon nitride on LaOCl for photocatalytic overall water splitting

In situ growth of crystalline carbon nitride on LaOCl with enhanced transfer and separation of photogenerated carriers for efficient photocatalytic overall water splitting.