Highest Hydrogen Evolution Rate Research Articles

Solution-Processable Donor-Acceptor Copolymer Thin Films for Efficient Visible-Light-Driven Photocatalytic Hydrogen Evolution.

Conjugated polymers (CPs) have been actively utilized as photocatalysts for hydrogen evolution due to their easy synthetic tunability to endow specific functionalities, including visible-light absorption, higher-lying LUMO energy for proton reduction, and sufficient photochemical stability. Enhancing interfacial surface and compatibility of hydrophobic CPs with hydrophilic water is the central focus to improve the hydrogen evolution rate (HER). Although a number of successful approaches have been developed in recent years, tedious chemical modifications or post-treatment of CPs make reproducibility of the materials difficult. In this work, a solution processable PBDB-T polymer is directly deposited on a glass substrate to form a thin film that is immersed in an aqueous solution to photochemically catalyze H2 generation. The PBDB-T thin film showed a much higher hydrogen evolution rate (HER) than the typical method of using PBDB-T suspended solids due to the enhanced interfacial area with a more suitable solid-state morphology. When the thickness of the thin film is reduced to dramatically improve the utilization of the photocatalytic material, the 0.1 mg-based PBDB-T thin film exhibited an unprecedentedly high HER of 120.90 mmol h-1 g-1.

Incorporating CdS and anchoring Pt single atoms into porphyrinic metal–organic frameworks for superior visible-light and sunlight-driven H2 evolution

Water splitting by photocatalytic semiconductors to produce hydrogen is considered one of the best ways to utilize solar energy. However, the recombination of electron-hole pairs in semiconductors such as cadmium sulfide (CdS) reduces the light-driven reaction efficiency. In addition, nanoparticles (NPs) of semiconductors tend to aggregate, resulting in decreased atom utilization. Rationally building composite photocatalysts by reducing nanoparticle aggregation and maximizing charge transport efficiency is thus seen as an attractive strategy for achieving high hydrogen evolution rates. Herein, we designed a new composite photocatalyst, CdS@PCN-222(Pt), by growing CdS in situ on a metal–organic framework (MOF) containing single Pt atoms. This catalyst exhibits an excellent hydrogen evolution activity of 71645 μmol/gCdS/h under visible light irradiation (λ ≥ 420 nm), which is around 110 times higher than pure CdS. Remarkably, CdS@PCN-222(Pt) also has an extremely high hydrogen evolution activity of 31326 μmol/gCdS/h under direct sunlight irradiation, far surpassing those of reported MOF-based photocatalysts. The charge-separation mechanisms were revealed by spectroscopic measurements, DFT calculations, and single crystal X-ray diffractions. The highly porous structure of PCN-222(Pt) results in the uniform distribution of CdS, and the anchored Pt single atoms achieve photo-induced electron transfer, inhibiting the recombination of photogenerated charge carriers. The results show that the synergistic effects between inorganic semiconductors and MOFs containing anchored single atoms enhance the photocatalytic activity for H2 generation under visible light and even sunlight. As a result, the findings offer important new perspectives that can be utilized in the design of high-performance composite photocatalysts in the future.

Atomically dispersed bismuth on ZnIn2S4 Dual-Functional photocatalyst for photocatalytic hydrogen production coupled with oxidation of aromatic alcohols to aldehydes

It is of great significance to develop a simple method of non-noble metal atomical dispersion to establish a dual-function photocatalysis system for the oxidation of aromatic alcohols to aldehydes, and to couple it with the photocatalytic hydrogen production, so as to fully utilize the photogenerated carriers. Herein, we report a noble metal-free photocatalyst decorated with atomic dispersed Bi atoms in ZnIn2S4 hierarchical structures by a one-pot method, for selective oxidation of R-PhCH2OH (R = H, Me, OH, Cl) coupled with high H2 evolution. Aberration corrected transmission electron microscopy and theoretical calculations demonstrated that Bi atoms are atomically dispersed and bridged with two S atoms. Atomically dispersed Bi provides the maximum atom efficiency and promotes light absorption to the near-infrared region. By excluding all wasteful sacrificial agents, Bi/ZnIn2S4 exhibits a high hydrogen evolution rate of 3658.8 µmol g-1h−1, which is approximately 14 times of that of bare ZnIn2S4 (256 µmol g-1h−1). This work provides insights into the effective utilization of photogenerated carriers in one system and the designing of promising photocatalysts with atomic precision.

Interfacial Chemical Bond Engineering in a Direct Z-Scheme g-C3N4/MoS2 Heterojunction.

The Z-scheme heterojunction shows great potential in photocatalysis due to its superior carrier separation efficiency and strong photoredox properties. However, how to regulate the charge separation at the nanometric interface of heterostructures still remains a challenge. Here, we take g-C3N4 and MoS2 as models and design the Mo-N chemical bond, which connects exactly the CB of MoS2 and VB of g-C3N4. Thus, the Mo-N bond could act as an atomic-level interfacial "bridge" that provides a direct migration path of charge carriers between g-C3N4 and MoS2. Experiments confirmed that the Mo-N bond and the internal electric field promote greatly the photogenerated carrier separation. The optimized photocatalyst exhibits a high hydrogen evolution rate that is about 19.6 times that of the pristine bulk C3N4. This study demonstrates the key role of an atomic-level interfacial chemical bond design in heterojunctions and provides a new idea for the design of efficient catalytic heterojunctions.

Hydrothermal deposition of high strength biocompatible magnesium phosphate coating through in situ conversion of AZ91D-3Ca magnesium substrate

Magnesium and its alloys are biodegradable and biocompatible with elastic modulus close to the natural bone which makes them suitable as an orthopedic implant. Poor corrosion resistance and high hydrogen evolution rate are two factors hindering their use as commercial implants. To overcome these challenges, a biocompatible magnesium phosphate coating was deposited using a single step hydrothermal method. Scanning Electron Microscopy (SEM/EDX) and X-Ray Diffraction (XRD) methods were used to analyze the structural and chemical compositions of these coatings. In addition, investigation on their adhesion, degradation, cellular proliferation, and gene expression were studied extensively. SEM analysis confirmed a uniform and defect-free deposition occurs in hydrothermal conditions. XRD validated the presence of Periclase (MgO), magnesium phosphate (Mg3(PO4)2) and Brucite (Mg(OH)2) phases. Degradation studies revealed the hydrogen evolution rate is remarkably decreased and corrosion properties were considerably improved as compared to the bare magnesium alloy. In-Vitro biocompatibility testing with pre-osteoblast (MC3T3-E1) via cell viability assay (Alamar blue reduction test) portrayed almost 100 % host cell proliferation both in coated and positive control samples after 8 days. Comparing coated and untreated magnesium alloy in SEM images, greater cell adhesion was seen to the coated surface. It is concluded that magnesium phosphate coatings can be used commercially as they are compact, highly crystalline, defect-free, bioresorbable, cytocompatibility, well-adhered, and protective in nature. Hence, phosphate-coated magnesium alloy is qualified to be used to protect biodegradable metallic implants.

Construction of Efficient D–A-Type Photocatalysts by B–N Bond Substitution for Water Splitting

Donor–acceptor (D–A)-type conjugated polymers are emerging as a promising platform for solar to chemical energy conversion, such as water splitting to H2 production. Disclosed herein is a new strategy that makes it possible to transform conventional conjugated polymers into D–A-type conjugated polymers by B–N bond substitution while retaining the original backbone. Using this method, we synthesize two conjugated polymers PCCP and PBNP, where PBNP containing the B–N bonds has a strong built-in electric field and a lower exciton binding energy (Eb) for solar-driven photocatalytic hydrogen evolution. PBNP without any co-catalyst addition exhibits a high hydrogen evolution rate (HER) of more than 9445 μmol g–1 h–1 for water splitting under AM 1.5G sunlight illumination (100 mW cm–2), a 28 times improvement relative to PCCP (333 μmol g–1 h–1). In addition, another contrasting BN-substituted D–A polymer PBNN also exhibits an excellent HER of 5740 μmol g–1 h–1. Theoretical and experimental studies confirm that the substitution of B–N bonds can completely change the electronic properties of the original polymer, allowing rapid charge separation and transfer. This work opens up new prospects for the preparation of efficient D–A conjugated polymer photocatalysts.

Effect of substitution position of carbazole based conjugated polymers on the photocatalytic hydrogen evolution activities of conjugated polymer/g-C3N4 heterojunction catalysts

Conjugated polymers/Graphitic carbon nitride (g-C3N4) based heterojunctions have been widely investigated in photocatalytic hydrogen Production (PHP). How to design high-performance conjugated polymers matched with g-C3N4 is the critical issue. Here, two linear D-A type conjugated polymers (BSO-S27 and BSO-S36) were synthesized by Suzuki coupling reaction between dibenzothiophene-5,5-dioxide and N-methylcarbazole units. The substitution sites of N-methylcarbazole are 2,7- positions for BSO-S27 and 3,6- positions for BSO-S36, respectively. The different substitution position leads to that BSO-S27 and BSO-S36 exhibit different optical absorption, energy level, and charge transport ability. Through the composition with g-C3N4 nanosheets (CN), BSO-S27/CN and BSO-S36/CN heterojunctions were formed. PHP results demonstrate that both BSO-S27 and BSO-S27/CN exhibit higher hydrogen evolution rate (HER) than BSO-S36 and BSO-S36/CN photocatalysts (BSO-S27: 1783.5 μmol g−1 h−1; BSO-S36: 1112.5 μmol g−1 h−1; BSO-S27/CN: 23078.2 μmol g−1 h−1; BSO-S36/CN: 15732.6 μmol g−1 h−1). And the hydrogen evolution mechanism of BSO-S27/CN and BSO-S36/CN are discussed deeply. These results demonstrate that regulating substitution position is a feasible method to design high-performance conjugated polymers or polymer heterojunctions as photocatalysts.

Hollow bi-Janus hetero-nanofibers as a bi-functional photoreforming catalyst for prominently boosting hydrogen evolution from water-pollutant system

Bi-functional photoreforming catalysts are promising for synergetic hydrogen evolution and pollutant removal through a water-pollutant system. The rational energy band and interface engineering are crucial in promoting their performance but are still challenging due to finely regulating nanoscale interface difficulties. Herein, single to bi-Janus interface engineering is adopted to develop hollow bi-Janus SrTiO3/ZnO/TiO2 hetero-nanofibers with gradient energy band and spatially separated redox surfaces via electrospinning married atomic layer deposition methods. The simulations indicate that these novel structures have a stronger internal electric field (5.72 ×106 V/m) than SrTiO3/ZnO (1.84 ×106 V/m) and ZnO/TiO2 (3.98 ×106 V/m) single-Janus hetero-nanofibers (SJ-HNFs), and more ordered electric field distribution than mixed hetero-nanofibers (MHNFs). Experimentally, they have better charge separation and directional carriers transfer path, as evidenced by photoluminescence, photovoltage, and photoelectrochemical investigations, along with photo-deposition probe experiments. The gradient energy band, directional charge transfer path, and spatially separated redox surfaces promote their photoreforming performance effectively, presenting a high photoreforming hydrogen evolution rate of 104.6 μmol g−1 h−1 in 10,000 ppm propranolol (corresponding degradation of 33.1% after 5 h), about 3.62, 4.27, and 3.11 times of ZnO/TiO2 SJ-HNFs, SrTiO3/ZnO SJ-HNFs and SrTiO3/ZnO/TiO2 MHNFs. This work provides a promising interfacial engineering strategy for designing photoreforming catalyst to simultaneously achieve energy conversion and environmental pollution treatment.

Bi-doped twin crystal Zn0.5Cd0.5S photocatalyst for highly efficient photocatalytic hydrogen production from water

Bi doped twin crystal Zn0.5Cd0.5S (Bi/ZCS) was prepared for the first time via a facile hydrothermal method and used as a highly efficient hydrogen production photocatalyst. Our study found that Bi doping in ZCS could significantly enhance the light absorption and promote the photogenerated carrier separation and transport owing to the formation of Bi impurity level inside the bandgap of ZCS. Accordingly, the photocatalytic hydrogen production performance of ZCS was greatly improved. The optimal Bi/ZCS photocatalyst showed a very high photocatalytic hydrogen evolution rate up to 1.09 mmol h−1 (10 mg catalyst was used) and a very high apparent quantum efficiency of 31.5% at the wavelength of 420 nm. Moreover, Bi/ZCS photocatalyst also demonstrated its practical application towards photocatalytic hydrogen production from seawater, realizing a superior hydrogen evolution rate which was nearly 4 times higher than the pristine ZCS, providing an effective and low-cost way to design high-efficiency solar hydrogen production photocatalysts.

Improved photocatalytic activity of TiO2 with a regulated covalent organic framework thin film.

In this work, one-dimensional TiO2 nanotube arrays are coupled with a covalent organic framework (COF) thin film with a controlled thickness to form a three-dimensional heterojunction, which exhibits a 3.3-fold higher hydrogen evolution rate than that of TiO2, and becomes active for CO2 conversion, compared to the bare COF. Such high activity results from the large difference in Fermi levels forming an internal electric field at the interface.

V-doped Ni2P nanoparticle grafted g-C3N4 nanosheets for enhanced photocatalytic hydrogen evolution performance under visible light.

Exploring low-cost and highly active photocatalysts with noble metal-free cocatalysts is of great significance for photocatalytic hydrogen evolution under simulated sunlight irradiation. In this work, a novel V-doped Ni2P nanoparticle loaded g-C3N4 nanosheet is reported as a highly efficient photocatalyst for H2 evolution under visible light irradiation. The results demonstrate that the optimized 7.8 wt% V-Ni2P/g-C3N4 photocatalyst exhibits a high hydrogen evolution rate of 271.5 μmol g-1 h-1, which is comparable to that of the 1 wt% Pt/g-C3N4 photocatalyst (279 μmol g-1 h-1), and shows favorable hydrogen evolution stability for five successive runs within 20 h. The remarkable photocatalytic hydrogen evolution performance of V-Ni2P/g-C3N4 is mainly due to the enhanced visible light absorption ability, the facilitated separation of photo-generated electron-hole pairs, the prolonged lifetime of photo-generated carriers and the fast transmission ability of electrons.

Facile implantation of imidazole-ring into graphitic carbon nitride for efficient photocatalytic hydrogen production

Polyimidazolium effectively extends the delocalization of the π-electron conjunction system of carbon nitride, endowing it with 4659 μmol h−1 g−1 of high hydrogen evolution rate and 10.1% of apparent quantum efficiency at a wavelength of 420 nm.

Highly efficient photocatalytic hydrogen production by platinum modified ferroelectric SrBi4Ti4O15

Combining metal with ferroelectrics is one of the reliable strategies to enhance the photocatalytic water splitting of ferroelectrics dramatically. However, the metal loading ratio is directly related to the synergistic effect of catalysts. In order to find the appropriate loading of Pt, we fabricated SrBi4Ti4O15 (SBTO) nanosheets (NSs) and deposited different amounts of Pt nanoparticles (NPs) to form heterojunction. The optoelectronic characterizations verified that the Pt-modified SBTO NSs have broadened absorption of visible light; produce more long-lived charge carriers. The photocatalytic hydrogen production can reach 11700 μmol g−1 under continuous illumination for 3 h from the sample containing 6 wt% Pt, showing a much higher hydrogen evolution rate than other ferroelectric materials under similar reaction systems. Our work provides a valuable and feasible solution to produce hydrogen from water.

Covalent Grafting of A Nickel Thiolate Catalyst onto Covalent Organic Frameworks for Boosted Photocatalytic Activity.

Covalent organic frameworks (COFs) have recently emerged as prospective photoactive materials with noble Pt cocatalyst for the photocatalytic hydrogen evolution. In this work, a series of SH-group-functionalized covalent organic frameworks, TpPa-1-SH-X, were prepared by reaction of p-phenylenediamine (Pa) and 1,3,5-triformylphloroglucinol (Tp), with p-NH2C6H4SH as a modulating agent. The reaction of TpPa-1-SH-X with Ni(II) acetylacetonate Ni(acac)2 gave nickel thiolate-immobilized TpPa-1 (TpPa-1-SNi-X). The highest hydrogen evolution rate was 10.87 mmol h-1 g-1, which was an enhancement of 16.47, 3.83, and 1.84 times than that of the parent TpPa-1, covalent-bond-free [(p-NH2C6H4S)2Ni]n/TpPa-1-SH-10, and 3 wt% Pt-deposited TpPa-1, respectively. This enhanced photocatalytic hydrogen evolution is ascribed to enhanced crystallinity, the use of Ni(II) thiolate as a cocatalyst and covalent bonding between the cocatalyst and TpPa-1.

G-C3N4-wrapped nickel doped zinc oxide/carbon core-double shell microspheres for high-performance photocatalytic hydrogen production

The development of efficient heterojunctions with enhanced photocatalytic properties is considered a promising approach for photocatalytic hydrogen production. In this study, graphitic carbon nitride (g-C3N4)-wrapped nickel-doped zinc oxide/carbon (Ni-ZnO@C/g-C3N4) core-double shell heterojunctions with unique core-double shell structures were employed as efficient photocatalysts through an innovative approach. Ni doping can enhance the intensity and range of visible light absorption in ZnO, and the carbon core coupled with the hollow double-shell structure can accelerate the charge transfer rate and improve the photon utilization efficiency. Meanwhile, the construction of the Z-scheme heterojunction extended the electron-hole pair transport path. In addition, the Z-scheme charge-transfer mechanism of Ni-ZnO@C/g-C3N4 under simulated sunlight was verified by photoluminescence (PL) and electron spin resonance (ESR) experiments. As a result, the obtained photocatalyst acquired a high hydrogen evolution rate of 336.08 μmol g−1h−1, which is 36.49 times higher than that of pristine ZnO. Overall, this work may provide a pathway for the construction of highly efficient photocatalysts with unique core-double shell structures.

Enhanced Photocatalytic Hydrogen Evolution from Organic Ternary Heterojunction Nanoparticles Featuring a Compact Alloy‐Like Phase

AbstractOrganic semiconductor nanoparticles (NPs) are attractive photocatalysts to produce hydrogen from water splitting. Herein, a ternary strategy of incorporating crystalline n‐type molecule IDMIC‐4F into the host system made of p‐type polymer PM6 and n‐type molecule ITCC‐M is demonstrated. ITCC‐M and IDMIC‐4F form compact alloy‐like composite with shorter lattice spacing in the ternary p/n heterojunction NPs, resulting in enhanced exciton dissociation and charge transfer characteristics. As the result, an unprecedented hydrogen evolution rate (HER) of 307 mmol h−1 g−1 and a maximum apparent quantum efficiency of 5.9% at 600 nm are achieved in the optimized ternary NPs (PM6:ITCC‐M:IDMIC‐4F = 1:1.3:0.2), which is among the highest HER from organic photocatalysts to the best of the authors’ knowledge. The alloy‐like composite also improves the operational stability of ternary NP photocatalysts. This study shows that synergizing two compatible n‐type small molecules to form alloy‐like composite is a promising approach to design novel organic photocatalysts for boosting the photocatalytic hydrogen evolution efficiency.

A Twin S-Scheme Artificial Photosynthetic System with Self-Assembled Heterojunctions Yields Superior Photocatalytic Hydrogen Evolution Rate.

Designing heterojunction photocatalysts imitating natural photosynthetic systems has been a promising approach for photocatalytic hydrogen generation. However, in the traditional Z-Scheme artificial photosynthetic systems, the poor charge separation, and rapid recombination of photogenerated carriers remain a huge bottleneck. To rationally design S-Scheme (i.e., Step scheme) heterojunctions by avoiding the futile charge transport routes is therefore seen as an attractive approach to achieving high hydrogen evolution rates. Herein, a twin S-scheme heterojunction is proposed involving graphitic C3 N4 nanosheets self-assembled with hydrogen-doped rutile TiO2 nanorods and anatase TiO2 nanoparticles. This catalyst shows an excellent photocatalytic hydrogen evolution rate of 62.37mmol g-1 h-1 and high apparent quantum efficiency of 45.9% at 365nm. The significant enhancement of photocatalytic performance is attributed to the efficient charge separation and transfer induced by the unique twin S-scheme structure. The charge transfer route in the twin S-scheme is confirmed by in situ X-ray photoelectron spectroscopy (XPS) and electron spin resonance (ESR) spin-trapping tests. Femtosecond transient absorption (fs-TA) spectroscopy, transient-state surface photovoltage (TPV), and other ex situ characterizations further corroborate the efficient charge transport across the catalyst interface. This work offers a new perspective on constructing artificial photosynthetic systems with S-scheme heterojunctions to enhance photocatalytic performance.

3-D nitrogen-doped carbon cage encapsulated ultrasmall MoC nanoparticles for promoting simultaneous ZnIn2S4 photocatalytic hydrogen generation and organic wastewater degradation

Simultaneous redox reactions on photocatalysts make it possible to use wastewater for hydrogen production. The controlled synthesis of ultrasmall metal carbides effectively enhances the photocatalytic efficiency under this system. Here, we report a new type of cocatalyst in which a three-dimensional (3-D) nitrogen-doped carbon cage (NGC) of metal–organic framework derivatives encapsulates ultrasmall MoC nanoparticles (MoC@NGC), promoting simultaneous degradation of organic pollutants and hydrogen production by ZnIn2S4 (ZIS). Characterization analyses showed that MoC accelerated the separation of the photogenerated carrier and effectively reduced the overpotential of hydrogen evolution, while NGC promoted the good dispersion of MoC particles and provided sufficient sites. The MoC@NGC/ZIS composite exhibited a high hydrogen (H2) evolution rate of 1012 µmol g–1h−1, which exceed that of ZIS loaded with platinum. In the coupled system, where the electron donor was replaced with rhodamine B (RhB), the mechanism analysis showed that RhB and the as-generated intermediates consumed holes and facilitated hydrogen evolution. In addition, we designed a combined photocatalytic anoxic and oxic sequence process to achieve the recovery of hydrogen energy during the treatment of dye wastewater. This study provides a new way for cooperation between energy development and environmental protection.

Highly Efficient Photocatalytic Hydrogen Evolution over Mo-Doped ZnIn2S4 with Sulfur Vacancies.

The introduction of impure atoms or crystal defects is a promising strategy for enhancing the photocatalytic activity of semiconductors. However, the synergy of these two effects in 2D atomic layers remains unexplored. In this case, the preparation of molybdenum-doped thin ZnIn2S4-containing S vacancies (Mo-doped Sv-ZnIn2S4) is conducted using a one-pot solvothermal method. The coordination of Mo doping and S vacancies not only enhances visible light absorption and facilitates the separation of photogenerated carriers but also provides many active sites for photocatalytic reactions. Meanwhile, the Mo-S bonds play function as high-speed channels to rapidly transfer carriers to the active sites, which can directly promote hydrogen evolution. Consequently, Sv-ZnIn2S4 with an optimized amount of Mo doping exhibits a high hydrogen evolution rate of 5739 μmol g-1 h-1 with a corresponding apparent quantum yield (AQY) of 21.24% at 420 nm, which is approximately 5.4 times higher than the original ZnIn2S4. This work provides a new strategy for the development of highly efficient and sustainable 2D atomic photocatalysts for hydrogen evolution.

Boosted solar water photoreduction by conjugated polymer-mediated tandem charge transfer

Semiconductor materials anchored with transition metal cluster are promising photocatalysts for photocatalytic hydrogen evolution. In this paper, Co, N-co-doped graphene modified thin mesoporous carbon nitride (Co-NG/TMCN) was be synthesized through electrostatic adsorption treatment. Extensive characterization was used to explore the morphology, structures and optical properties of the as-prepared photocatalysts. The 10 wt% Co-NG/TMCN exhibited the high photocatalytic hydrogen evolution rate (2949 μmol g−1) within 4 h visible light irradiation, which was about 113 times than that of the pure TMCN (26 μmol g−1). Co-NG material with excellent electrical conductivity played a major role in accelerating charge transfer from TMCN material to cobalt atomic clusters. The photocatalytic hydrogen evolution performance of Co-NG/TMCN material was effectively improved. Consequently, a feasible approach for doping transition metal clusters to enhance photocatalytic activity was provided.