Optimal H2 Production Research Articles

The Precision Defect Engineering with Nonmetallic Element Refilling Strategy in g-C3 N4 for Enhanced Photocatalytic Hydrogen Production.

Traditional defect engineering and doping strategies are considered effective means for improving H2 evolution, but the uncontrollability of the modification process does not always lead to efficient activity. A defect-induced heteroatom refilling strategy is used here to synthesize heteroatoms introduced carbon nitride by precisely controlling the "introduction" sites on efficient N1 sites. Density functional theory calculations show that the refilling of B, P, and S sites have stronger H2 O adsorption and dissociation capacity than traditional doping, which makes it an optimal H2 production path. The large internal electric field strength of heteroatom-refilled catalysts leads to fast electron transfer and the hydrogen production of the best sample is up to 20.9mmolg-1 h-1 . This work provides a reliable and clear insight into controlled defect engineering of photocatalysts and a universal modification strategy for typical heteroatom and co-catalyst systems for H2 production.

Preparation, characterization and electronic properties of LaFeO3 perovskite as photocatalyst for hydrogen production

Perovskite-type LaFeO3 was successfully used as photocatalyst for the H2 production. It was prepared by a conventional sol-gel technique via the nitrate route. X-Ray fluorescence/Energy Dispersive X-Ray fluorescence (XRF), X-Ray Diffraction (XRD), X-Ray photoelectron spectroscopy (XPS), UV–Visible diffuse reflectance, FTIR spectroscopy, Scanning Electron Microscopy (SEM/EDX) and specific surface area were deployed to characterize the synthetized material after heat-treated at 850 °C. LaFeO3 crystallizes in a cubic structure (Space Group: Pm3 m) with a crystallite size of 16 nm and BET surface area of 12 m2/g. Field-dependent magnetization was measured at 300 K in the region (±25 kOe) and the perovskite exhibits a high magnetism with a saturation magnetization (0.15 emu/g). Such result indicates that the Fe-3d are in localized high spin state. LaFeO3 has a narrow band gap of 2.08 eV determined by diffuse reflectance resulting to the crystal field splitting of 3d orbital of Fe3+ octahedrally coordinated with an internal d-d transition. Cyclic voltammetry showed the reduction of adsorbed H2O molecules to gaseous hydrogen at −0.7 VSCE, a potential less cathodic than the conduction band (−0.45 VSCE). The latter was determined from the capacitance measurements in alkaline electrolyte (NaOH 0.1 M) where the perovskite exhibits a stability with an exchange current density of ∼0.4 mA cm−2. The photocatalytic activity reveals an optimal H2 production of 99 μmol after 20 min at 50 °C in NaOH medium and a catalyst mass of 50 mg, under visible light irradiation (13 W) in the presence of thiosulfate S2O32− as hole scavenger.

Peripheral nucleic bases boost H2 production by synthetic molecular catalysts in acidic water.

The strategic inclusion of nucleic bases adenine, cytosine, and thymine, in the form of outer coordination sphere, positively impacts the electro- and photocatalytic H2 production by cobaloxime cores. These cobaloxime derivatives showcased their optimal H2 production in acidic media due to specific protonation of adenine and cytosine below pH 5.0.

Pyrolysis of de-fatted microalgae residue: A study on thermal-kinetics, products’ optimization, and neural network modelling

The present work focused on the pyrolysis-based valorization of microalgae biomass residual for the generation of sustainable fuel and value-added chemicals. Key pyrolysis factors, including temperature, residence time, particle size, and heating rate, were modeled via an artificial neural network (ANN) and response surface methodology (RSM) models. The use of such an integrated technique was able to conquer the individual constraints of both modeling approaches. RSM model for H2-rich syngas demonstrated that the value; R2 = 0.99, minimum p = 0.00, and maximum F = 3877.16 has close relation among the statistical parameters. The ANN model for H2-rich syngas revealed that higher R2 = 0.9985 and lower RSME = 0.1038 were obtained for the training phase, while; the higher R2 and lower RSME values of 0.9862 and 0.2661 were estimated for the training phase hence showed a better agreement among the parameters. Optimum H2 production of 44.46 vol% was produced at temperature = 516.76 °C, residence time = 17.7 min, particle size = 0.23 mm, and heating rate = 17.37 °C/min. All the pyrolytic products have been characterized in detail and are recommended for high end-use. The GC/MS technique revealed that bio-oil was constituted of various organic complexes, which could be used as a substitute for hydrocarbon fuels after undergoing certain upgradation procedures (e.g., hydrotreating, hydrodeoxygenation, hydrodenitrogenation, and hydrocracking) and extracted into different chemicals. In addition, the biochar was characterized using the SEM technique, which also demonstrated its potential as fuel and in a variety of other applications. The study showed that de-fatted Chlorella sorokiniana residue (De-CR) could be efficiently employed to produce bio-energy precursors.

Highly efficient visible-light-driven photocatalytic H2 production over a p−n Mn0.2Cd0.8S/NiCo2O4 heterojunction modified with Ni2P

In this work, the Mn0.2Cd0.8S/NiCo2O4 composite modified with Ni2P as a co-catalyst was fabricated via a simple two-step hydrothermal method. The as-prepared ternary Mn0.2Cd0.8S/NiCo2O4/Ni2P composite displayed excellent H2 production performance. The ternary composite loaded with 5 wt% NiCo2O4 and 2 wt% Ni2P obtained the optimal H2 production performance of 24.47 mmol g−1 h−1 and a maximum AQE of 23.75%. The enhanced H2 production activity was assigned firstly to efficient spatial charge separation through the p−n Mn0.2Cd0.8S/NiCo2O4 heterojunction and secondly to sufficient surface active sites provided by Ni2P co-catalysts. This research provides a new approach to design effective ternary heterojunction.

Construction of core–shell FeS2@ZnIn2S4 hollow hierarchical structure S-scheme heterojunction for boosted photothermal-assisted photocatalytic H2 production

Photothermal effect materials play an essential role in the field of solar energy utilization, and can provide additional capacity supply during photocatalytic reactions. Herein, the core–shell FeS2@ZnIn2S4 S-scheme heterojunction with coating the ZnIn2S4 nanosheets on the FeS2 raspberry-like hollow spheres was fabricated for photothermal-assisted photocatalytic H2 production. In this catalyst design system, the hollow spherical FeS2 was employed as a photothermal substrate to endow more energy for the ZnIn2S4 photo-generated charge carriers to accelerate the charge migration and elevate the temperature of the reaction system, and the interface charge transfer of the S-scheme mechanism realizes the spatial separation of the charge carriers. Meanwhile, the ZnIn2S4 nanosheet coating coated on the surface of the FeS2 hollow sphere effectively prevented the heat loss of the hybrid system. Under simulated solar irradiation (AM 1.5G), the optimal H2 production rate of the FS@ZIS heterojunction is as high as 5.05 mmol/g/h in the absence of Pt as the co-catalyst (AQE of 13.4 % at 420 nm), which is 47.9 and 53.7 times higher than that of pristine ZnIn2S4 and FeS2, respectively. Furthermore, the hydrogen production tests in simulated seawater demonstrate the extensive environmental adaptability of the as-prepared FS@ZIS S-scheme heterojunction. Our work provides a feasible strategy to construct an S-scheme heterojunction system with photothermal assistance for efficient utilization and conversion of solar energy.

Highly dispersed platinum-anchored g-C3N4 nanotubes for photocatalytic hydrogen generation

To overcome the shortcoming of rapid recombination of photoexcited electron-hole pairs of g-C3N4, noble metals are usually loaded as co-catalyst. However, conventional chemical reduction often brings about the loading of noble metal aggregates or nanoparticles that leads to a low atomic utilization efficiency. In this work, Pt atoms are highly dispersed on S-doped g-C3N4 nanotubes through in situ pyrolysis of H2PtCl6. Diffuse reflection infrared Fourier transform spectrum and XPS spectrum reveal that Pt exists in the state of +2 chemical valence and is anchored by coordination with diatomic N and S of g-C3N4, leading to a high dispersion and stabilization of Pt atoms in g-C3N4 nanotube. The optimal H2 production rate (0.3 wt% Pt) is 5304 μmol h−1g−1 and the turnover frequency (TOF) is 321.7 h−1 upon visible light illumination (λ > 420 nm), that is 3.2 times as high as Pt nanoparticle loaded g-C3N4 nanotube with the same loading content. Our work provides a new way to anchor noble metal on photocatalyst via diatomic coordination and enhance the atomic utilization efficiency of noble metal co-catalyst. Moreover, the unique electronic structure of Pt2+ with electron-deficient 5d orbitals decreases the kinetic energy barrier and promotes H2 evolution on the surface of photocatalyst.

Z-scheme g-C3N4/ZnO heterojunction decorated by Au nanoparticles for enhanced photocatalytic hydrogen production

The construction of heterojunction photocatalysts is an effective and widespread approach to solving global environmental issues. Herein, we designed and fabricated a Z-scheme g-C3N4/ZnO/Au heterojunction using a simple chemical method for photocatalytic H2 production under UV–Visible light irradiation. The g-C3N4/ZnO/Au-2 composite has an optimal photocatalytic H2 production rate of 46.46 μmol∙g−1∙h−1, representing 25.2-fold and 30.4-fold enhancements compared with a g-C3N4/ZnO-2 composite and bare g-C3N4, respectively. The decorated Au nanoparticles not only enhance the absorption of visible light by the LSPR effect, but also act as an electron mediator to accelerate the electrons transfer from ZnO to g-C3N4. The improved photocatalytic activity of the g-C3N4/ZnO/Au-2 composite can be attributed to the effectively suppressed recombination of photogenerated electron and hole pairs. The mechanism of the photocatalytic hydrogen evolution process had been studied by UV–vis diffuse reflectance spectroscopy (UV–vis DRS), Ultraviolet photoemission spectroscopy (UPS), photoluminescence (PL), transient photocurrent responses, electrochemical impedance spectroscopy (EIS), and electron spin resonance (ESR). This work provides a strategy for the design and synthesis of an environmentally friendly Z-scheme heterojunction for photocatalytic H2 evolution applications.

1D/2D CeO2/ZnIn2S4 Z-scheme heterojunction photocatalysts for efficient H2 evolution under visible light

The development of a high-efficiency photocatalyst having favorable charge transfer has become an important scientific approach for solar-to-fuel conversion. In this study, the one-dimensional (1D)/2D CeO2/ZnIn2S4 (ZIS) photocatalyst having a Z-scheme heterojunction has been successfully fabricated using the in situ growth of ZIS nanosheets on the CeO2 nanorod surfaces. The optimal H2 production rate of 3.29 mmol g−1 h−1 was achieved with the 15% CeO2/ZIS sample under visible light without any cocatalyst; furthermore, this value was 2.7 and 92.6 times higher than those of pristine ZIS and CeO2, respectively. The remarkable photocatalytic activity can be attributed to the efficient separation of photogenerated carriers as well as the formation of the Z-scheme heterojunction, which maintained the strong reduction of electrons in ZIS for H2 production. The presence of an internal electric field between CeO2 and ZIS has been demonstrated by both density functional theory calculations and Kelvin probe force microscopy. The Z-scheme transfer of photogenerated carriers in the CeO2/ZIS heterojunction has been confirmed by electron paramagnetic resonance spectroscopy and in situ irradiated X-ray photoelectron spectroscopy. This study presents certain insights into the development of efficient Z-scheme photocatalysts for H2 evolution from solar water splitting.

Photocatalytic H2 production over S-scheme Co3Se4/TiO2 nanosheet with super-hydrophilic surface

Photocatalytic H2 evolution represents a sustainable technology to acquire green energy via a solar energy conversion process. The development of photocatalysts with simple preparation and superior activity is still highly desired. In this work, the H2 evolution activities of cobalt selenide (Co3Se4) microspheres decorated TiO2 were investigated for the first time. The 25 wt% Co3Se4/TiO2 hybrid delivers an optimum H2 production rate of 6065 μmol·g−1·h−1 in 20 vol% TEOA under 300 W Xe lamp irradiation, which is 12.5 and 13.4 times that of pristine TiO2 (484 μmol·g−1·h−1) and pure Co3Se4 (453 μmol·g−1·h−1), respectively. The enhanced activity benefits from the S–scheme heterojunction formed between Co3Se4 and TiO2, which can obviously promote the separation of charge carriers and reduce the overpotential of H2 generation. Besides, the surface composition of the sample after reaction was revealed through XRD, TEM, XPS and water contact angle measurements, the results show that the microstructure of the composite sample remains unchanged after reaction, and a thin oxide or hydroxide layer was in–situ formed on the surface of Co3Se4, leading to a super–hydrophilic surface of Co3Se4/TiO2 and endowing with long reaction stability. This work broadens the application of Co3Se4 in energy conversion and provides a promising option to replace traditional noble metal photocatalysts.

High-efficient solar-driven hydrogen production by full-spectrum synergistic photo-thermo-catalytic methanol steam reforming with in-situ photoreduced Pt-CuOx catalyst

Synergy between the intrinsic photon and thermal effects from full-spectrum sunlight for H2 production is considered to be central to further improve solar-driven H2 production. To that end, the photo-thermo-catalyst that demonstrates both photoelectronic and photothermal conversion capabilities have drawn much attention recently. Here, we propose a novel synergistic full-spectrum photo-thermo-catalysis technique for high-efficient H2 production by solar-driven methanol steam reforming (MSR), along with the Pt-CuOx photo-thermo-catalyst featuring Pt-Cu/Cu2O/CuO heterojunctions by Pt-mediated in-situ photoreduction of CuO. The results show that the H2 production performance rises superlinearly with increasing light intensity. The optimal H2 production rate of 1.6 mol g−1 h−1 with the corresponding solar-to-hydrogen conversion efficiency of 7% and the CO selectivity of 5% is achieved under 15 × sun full-spectrum irradiance (1 × sun = 1 kW m−2) at 180 °C, which is much more efficient than the previously-reported Cu-based thermo-catalysts for MSR normally operating at 250∼350 °C. These attractive performances result from the optimized reaction kinetics in terms of intensified intermediate adsorption and accelerated carrier transfer by long-wave photothermal effect, and reduced activation barrier by short-wave photoelectronic effect, due to the broadened full-spectrum absorbability of catalyst. This work has brought us into the innovative technology of full-spectrum synergistic photo-thermo-catalysis, which is envisioned to expand the application fields of high-efficient solar fuel production.

Optimization of municipal solid waste air gasification for higher H2 production along with the validation via kinetics and statistical approaches

This study aimed to investigate municipal solid waste (MSW) gasification to produce hydrogen (H2) at optimum levels. Therefore, the gasification of MSW was initially investigated using a thermogravimetric analyzer (TGA) coupled with mass spectrometer (MS). The leading gases detected by the MS included; H2, CO, CO2, and CH4. Afterward, the gasification was carried out in the tubular batch reactor to investigate the composition, gasification products, and syngas properties (H2/CO molar ratio, H2 + CO, lower heating value (LHV), H2 yield)) under some influencing parameters. Due to the dominating reaction temperature, a significant increase in H2 (25.41% to 39.70%) and gas (57.10–74.93%) production accompanied a notable decrease in tar (16.48–8.54%) and char (28.40–15.52 wt%) contents. Flynn-Wall-Ozawa (FWO) and central composite design (CCD) models were applied to investigate kinetic and statistical parameters which showed better results. Optimum H2 production of 45.79 mol% with H2/CO, H2 + CO, LHV, and yield of 1.78, 72.78 mol%, 9.96 MJ/Nm3, and 13.83 mol kg-MSW−1 respectively was obtained at optimal temperature, particle size, and heating rate of 703.49 ℃, 3.21 mm, and 5 ℃/min respectively, which can be an appropriate fuel for Fischer Tropsch process for manufacturing of transportation fuels.

Techno-economic feasibility assessment of sorption enhanced gasification of municipal solid waste for hydrogen production

Waste-to-fuel coupled with carbon capture and storage is forecasted to be an effective way to mitigate the greenhouse gas emissions, reduce the waste sent to landfill and, simultaneously, reduce the dependence of fossil fuels. This study evaluated the techno-economic feasibility of sorption enhanced gasification, which involves in-situ CO2 capture, and benchmarked it with the conventional steam gasification of municipal solid waste for H2 production. The impact of a gate fee and tax levied on the fossil CO2 emissions in economic feasibility was assessed. The results showed that the hydrogen production was enhanced in sorption enhanced gasification, that achieved an optimum H2 production efficiency of 48.7% (T = 650 °C and SBR = 1.8). This was 1.0% points higher than that of the conventional steam gasification (T = 900 °C and SBR = 1.2). However, the total efficiency, which accounts for H2 production and net power output, for sorption enhanced gasification was estimated to be 49.3% (T = 650 °C and SBR = 1.8). This was 4.4% points lower than the figure estimated for the conventional gasification (T = 900 °C and SBR = 1.2). The economic performance assessment showed that the sorption enhanced gasification will result in a significantly higher levelised cost of hydrogen (5.0 €/kg) compared to that estimated for conventional steam gasification (2.7 €/kg). The levelised cost of hydrogen can be reduced to 4.5 €/kg on an introduction of the gate fee of 40.0 €/tMSW. The cost of CO2 avoided was estimated to be 114.9 €/tCO2 (no gate fee and tax levied). However, this value can be reduced to 90.1 €/tCO2 with the introduction of an emission allowance price of 39.6 €/tCO2. Despite better environmental performance, the capital cost of sorption enhanced gasification needs to be reduced for this technology to become competitive with mature gasification technologies.

Hydrogen production potential from agricultural biomass in Punjab province of Pakistan

Depleting resources and popping environmental concerns instigate the development of sustainable and clean energy solutions. Amongst others, Hydrogen (H2) is an imperious alternative due to the lowest emissions, higher calorific value, and usability. It has great relevance in Pakistan due to sequester Agricultural biomass potential that can be used as feedstock for H2 production. So, this study estimates the H2 production potential from agricultural biomass (rice, sugarcane, cotton, wheat, and maize) of Punjab, Pakistan. In doing so, simulations are performed using Aspen Plus under various conditions to derive an optimal value of H2 output. The results indicate significant heterogeneity across districts and crop residues types. Therefore, the Geographic Information System (GIS) is used to draw the spatial distribution of optimal H2 production across crops and districts. The simulated results reveal that Punjab province has the potential to produce 2619.90 × 103 Metric tons (MT)/year H2, and the highest potential derives from sugarcane trash (1012.77 × 103 MT/year), followed by maize straw (433.67 × 103 MT/year). The estimated H2 potential (2.62 million MT/year) can be used in industries, transportation, and urea production as a sustainable alternative in Pakistan.

P-Type AsP Nanosheet as an Electron Donor for Stable Solar Broad-Spectrum Hydrogen Evolution.

Although research progress on mimicking natural photosynthesis for solar-to-fuel conversion has been continuously made, exploring broadband spectral-responsive materials with suitable band positions and high stability still remains a huge challenge. Herein, we, for the first time, report novel AsP nanosheets (NSs) with P-type semiconducting property and enough negative conduction band, which can work as a stable near-infrared (NIR) region-responsive electron donor for water reductive hydrogen (H2) production. To mimic photosystem I, Au nanorods (NRs) act as electron transport media, which are also responsible for the enhanced electric field nearby, and 1T-MoS2 NSs as a hydrogen evolution catalyst are orderly coupled with AsP NSs with a sheet-rod-sheet structure by electrostatic self-assembly. The cascaded band level alignment enables unidirectional electron flow from AsP to Au and then to MoS2, and the optimum H2 production rate of the MoS2-Au-AsP ternary heterojunction reaches 125.52 μmol g-1 h-1 with good stability even after being stored for several months under light irradiation with a wavelength longer than 700 nm. This work provides a platform that is energetically tailored to drive a solar broad-spectrum fuel generation, including CO2 reduction and N2 fixation.

Optimal H2 Production and Consumption for Improved Utility Operations: Path to Net-Zero Emission Energy Production

Due to population growth, electricity demand increases significantly, and a continued reliance on fossil fuels will contribute to the global warming crisis. According to the U.S. Energy Information Administration, electricity production accounts for 33% of annual carbon dioxide (CO2) emissions of which 65% of this amount is produced by large-scale coal and natural gas power plants [1]. As a consequence, the global temperature is estimated to rise about 1.5°C to 2°C on average by the year 2050. To that end, the U.S. government set a nationwide Net-Zero Emission goal by the year 2050 in which the power sector, especially utilities and generation companies must supply their load with green energy by 2035, and the transportation sector must be electrified completely by 2050 [2]. Additionally, due to the advancements in distributed energy resources (DERs) technologies, such as solar, wind, storage, hydrogen (H2), and demand response programs, the capital costs of these technologies will drop by 60%-70% until 2050 according to the National Renewable Energy Lab’s (NREL) reports, accelerating the growing trend of utilizing more DERs [3].In recent years, H2 energy has demonstrated a great potential for large deployment from economic, environmental, and technical viewpoints. Generally, H2 energy can be produced, compressed, stored, and consumed using an electrolyzer, a compressor, a storage tank, and a fuel cell (FC) [4]. There are various technologies for water electrolysis such as alkaline, proton exchange membrane (PEM), and solid oxide electrolysis, in which electricity is used to separate water into oxygen and hydrogen. The generated H2 can then be compressed and stored in a storage tank, in the form of cryogenic liquid or high-pressure gas. The most important applications of H2 energy are 1) power generation with stationary/mobile FC units; 2) transportation fuel for light- and heavy-duty FC vehicles; 3) fuel for residential and commercial buildings (e.g., space and water heating); 4) feedstock for ammonia production, etc., 5) assist utilities with technical concerns such as PV smoothing, voltage, and frequency regulations, etc. [5] [6].In this study, we consider the perspective of the distribution system operator (DSO) that manages the DERs, especially H2 production and consumption by H2 systems, to reach the goal of net-zero emission energy production. It should be mentioned that a vertically integrated design is considered for the operation of the distribution network. To have realistic analysis of distribution network considering the power flow and voltage challenges, a standard 33-node distribution network [7] based on Fig. 1 including utility-operated natural gas power plants (combined cycle units and combustion turbine units), PV units, Battery energy storage (e.g., Li-ion batteries, Vanadium Redox flow batteries, etc.), and H2 systems (including electrolyzers, compressors, storage tanks, and FC units) are considered. Different types of voltage-dependent loads are considered such as critical, moderately critical, and non-critical loads to resemble load types like hospitals, offices, grocery stores, etc. The goal of normal operation from grid operators' (utilities) perspective is to operate these assets to minimize the total operational and investment costs and maximize the green energy production for the power sector. Interested readers are encouraged to check [8] for more information.Simulation results for different case studies assume costs for the year 2050, and demonstrate that with considering H2 systems and Redox flow batteries, the net-zero emission energy production for electricity demand supply is achieved in high PV penetration levels while addressing the technical and physical network constraints.[1] “U.S. Energy Information Administration,” [Online].https://www.eia.gov/tools/faqs/faq.php?id=77&t=11.[2] “International Energy Agency,” [Online].https://www.iea.org/reports/net-zero-by-2050.[3] L. J. Vimmerstedt, C. R. Augustine, P. C. Beiter, W. J. Cole, D. J. Feldman, P. Kurup, E. J. Lantz, R. M. Margolis, T. J. Stehly, C. S. Turchiet al., “2018annual technology baseline (atb),” National Renewable Energy Lab.(NREL), Golden, CO (United States), Tech. Rep., 2018.[4] H. Haggi, W. Sun, J. M. Fenton, and P. Brooker, “Risk-averse cooperative operation of PV and hydrogen systems in active distribution networks, ”IEEE Systems Journal, 2021.[5] A. Kovaˇc, M. Paranos, and D. Marciuˇs, “Hydrogen in energy transition: A review,” International Journal of Hydrogen Energy, 2021.[6] “Road Map to US Hydrogen Economy,” [Online].http://www.fchea.org/us-hydrogen-study.html.[7] M. E. Baran and F. F. Wu, “Network reconfiguration in distribution systems for loss reduction and load balancing,” IEEE Power Engineering Review, vol. 9, no. 4, pp. 101–102, 1989.[8] H. Haggi, W. Sun, J. M. Fenton, and P. Brooker, “Proactive scheduling of hydrogen systems for resilience enhancement of distribution networks,”2021IEEE Kansas Power and Energy Conference (KPEC), 2021. Figure 1

Benzenesulfonyl chloride-incorporated g-C3N4 for photocatalytic hydrogen generation by using the hydrolysate of poly(lactic acid) as sacrificial reagent

To overcome the shortcomings of insufficient absorption of visible light and rapid recombination of photoexcited electron-hole pairs of g-C3N4, we synthesized benzenesulfonyl chloride incorporated g-C3N4 (BS-CN) with narrower bandgap and stronger absorption in visible light region thanks to extension of π-electron delocalization. A quick intramolecular electron transfer was realized via intramolecular donor-acceptor conjugation in BS-CN. Different from commercial sacrificial reagents, lactate, hydrolyzed by poly(lactic acid) (PLA) in KOH solution, was used as sacrificial reagent in this work. The optimal H2 production rate over Pt-loaded (1 wt%) BS5-CN was 1890 µmol h−1g−1 under visible light illumination (λ > 420 nm), roughly 2.8 times as high as pure g-C3N4. 1H NMR spectrum indicated that lactate was oxidized into formate and acetate. Our work manifests that the abandoned PLA plastic can be transformed into hydrogen energy and valuable organic chemicals simultaneously via photocatalytic reaction, thus inhibiting “white pollution”.

In-situ construction of sequential heterostructured CoS/CdS/CuS for building “electron-welcome zone” to enhance solar-to-hydrogen conversion

Photocatalysis has been facing challenging problems especially the inefficient photocarriers transfer at the interfaces. Here, based on Ksp difference, we prepare the sequential heterojunction of CoS/CdS/CuS via sequential cation exchange strategy, and propose the concept of "electron-welcome zone", where the point-to-point contact can be formed at the interface, thus providing continuous electron transport channels. HAADF-STEM EDS line test indicates the formation of designed structures, and the p/n junction is confirmed by band structure and Mott-Schottky analysis. Theoretical calculation indicates that CoS reduces the Gibbs free energy of the reaction. TRPL spectra show that the existence of "electron welcome zone" greatly improves the lifetime of electrons. This sequential structure enable the optimal H2 production rate to reach 123.2 mmol g−1 h−1 with AQE of 45.6%, which is among the highest values of CdS-based photocatalysts. This work opens new way to efficient photogenerated carrier transfer channel for solar-energy conversion.

CoCO3 hierarchical structure embedded on g-C3N4 nanosheets to assemble 3D/2D Z-scheme heterojunction towards efficiently and stably photocatalytic hydrogen production

Structure and interface control of heterojunction is usually a challenging issue to improve the photocatalytic performance. Herein, a new 3D/2D CoCO3/g-C3N4 heterojunction is assembled by embedding hexahedral CoCO3 on g-C3N4 nanosheets. The unique step-like hierarchical structure of CoCO3, the formed built-in electric field and Z-scheme charge transfer behavior at the interface jointly drive the high-efficient separation of photogenerated carriers to boost the photocatalytic H2 production. It achieves the optimal H2 production rate that is almost 2.6 times than g-C3N4, apparent quantum efficiency (AQE) of 10.1% at 400 nm and continuous running of 60 h over the 3D/2D CoCO3/g-C3N4 heterojunction. This work endows a fresh structural control strategy for the fabrication of 3D/2D Z-scheme heterojunction to improve the photocatalytic H2 production performance.

Properly aligned band structures in B-TiO2/MIL53(Fe)/g-C3N4 ternary nanocomposite can drastically improve its photocatalytic activity for H2 evolution: Investigations based on the experimental results

The development of new tools that could meet the demand of sustainable energy production has attracted worldwide scientific attention. Over the past few decades, significant research efforts have been carried out to efficiently reduce water to H2 (green fuel) over semiconductor photocatalysts. Numerous semiconductor photocatalysts have been employed in photocatalysis for optimum H2 production. All the techniques were chosen based on their flexibility, cost-effectiveness, and ease of availability. Recently, polymeric carbon nitride (g-C3N4) received worldwide attention in visible light photocatalysis for energy and environmental applications due to its low price, robust nature, and superior thermal stability. Nevertheless, g-C3N4 (CN) exhibits shortfalls such as high charge carrier's recombination rate and weak reduction ability. To overcome these drawbacks, herein, for the first time we have fabricated B-TiO2/MIL-53(Fe)/CN ternary composite via hydrothermal and wet-chemical methods. The resultant B-TiO2/MIL53(Fe)/CN ternary composite shows drastically improved photocatalytic activity for hydrogen evolution compared to the bare CN, B-TiO2, and MIL53(Fe) components. The B-TiO2/MIL53(Fe)/CN ternary composite produced approximately 166.3 and 581.2 μmol h−1 g−1 of hydrogen under visible light and UV–visible light irradiations, respectively, with the assistance of co-catalyst Pt. Photo-luminescence (PL) and the fluorescence (FL) spectroscopy measurements reveal that the enhanced photoactivity is due to the greatly promoted charge carrier's separation and transfer at the interfacial contact of the well-aligned three-component systems. This work will promote the design and development of efficient photocatalyst based on CN for clean energy production and environmental purification.