Solar Hydrogen Production Research Articles

A review on the recent advances in the design and structure–activity relationship of TiO2-based photocatalysts for solar hydrogen production

The recent progress in visible light driven photocatalysis by describing the integration of TiO2 with variety of materials, and how it helps in tailoring electronic, structural and optical properties towards improved solar H2 production activity.

Analysis of prospective demand for hydrogen in the road transportation sector: Evidence from 14 countries

This paper precisely estimates the looming demand for hydrogen within the transportation sector, spanning 14 pivotal G20 nations from 2022 to 2050, anchored in the global vehicle hydrogen market penetration rate. Employing a robust techno-economic modeling methodology and leveraging Geographic Information System (GIS) for enriched visualization, it unveils distinct environmental dividends across three thoughtfully devised scenarios: Business-as-Usual, Moderate, and Aggressive. Findings herald India and China as pinnacles of hydrogen demand, with South Korea and Japan tailing closely. The study forecasts the energy consumption for solar hydrogen production in G20 countries to oscillate between 3.02 and 2.89 million GWh in 2022, while production costs are anticipated to range from $8.47/kg to $10.01/kg. In an assertive scenario, the paper illuminates a pathway towards achieving a significant CO2 reduction, unmasking environmental savings of up to a staggering 48%, equivalent to 1.5 million mtCO2, by 2050.

Effects of transition metals (Fe, Co) on the physical and photoelectrochemical hydrogen generation properties of copper oxide nanoparticulate films

The composites of some transition metal oxides are currently attracting interesting roles in various fields of technology and industry. The present work attempts to tune the properties of copper oxide (CuO) for hydrogen energy generation. Iron (Fe) and cobalt (Co) were intentionally doped at precise contents into CuO thin films. X-ray diffraction (XRD) indicated that the successful substitution of Fe and Co on the Cu sites created induces pressure (tensile) stress in the lattice. Fe doping deteriorated the films' crystallinity and increased the dislocation density from 1.82 × 10−3 to 4.36 × 10−3 nm−2, while Co codoping displayed unsystematic behavior. The scanning electron microscope (SEM) images showed that the films have smooth surfaces comprising a huge number of particles/unit area with a narrow size distribution. The energy-dispersive X-ray (EDX) analysis confirmed the presence of both Fe and Co with almost the pre-calculated ratios. The optical measurement showed that increasing the Fe contents increases the absorption coefficient of CuO and narrows its optical band gap from 1.7 to 1.55 eV. The photoluminescence (PL) intensity increases for Fe-doped CuO films whereas quenched when doped with Co. A series of photoelectrochemical (PEC) measurements were conducted to evaluate the performance of the prepared films in the production of solar hydrogen. The CuO–6%Fe film showed high photocatalytic performance for H2 generation from H2O splitting over a wide wavelength range of sunlight with long-term photostability. The photocurrent density of CuO–6%Fe film is about 155 times more than those obtained from pure CuO film. The incident photon-to-current efficiency (IPCE) and the solar-to-hydrogen efficiency (ηSTH) of CuO–6%Fe film were 5.98 % at 307 nm and 0.94 % under Xenon illumination, respectively. Hence, this work proposed an efficient and reasonable technique to enhance the performance of a CuO-based photoelectrode for solar hydrogen production.

Two birds with one stone: Functionalized wood composites for efficient photocatalytic hydrogen production and solar water evaporation

Maximizing solar energy utilization is a persistent challenge in photo catalysis, which determines sustainable solar-driven photocatalytic process. Photo thermal-coupled photo catalysis is considered as a promising solution to tackle the issues of sustainable energy scarcity and environmental pollution by harvesting the full-spectrum solar energy. Herein, a highly efficient photo thermal-accelerated photo catalysis system is elaborately established, in which the assembled carbonized stick/Nb2C MXene evaporator can heat water into vapor and the integrated g-C3N4 photocatalyst further enables high-efficiency photocatalytic hydrogen production. The designed hyperboloid wood-based architecture possesses a multiphase interface of water steam/catalyst/hydrogen to reduce the transport resistance of hydrogen gas in liquid and ultimately maximize the output of hydrogen energy. Consequently, this coupled photothermal-photocatalytic system achieves a stable solar evaporation rate of 2.16 kg m-1 h-1 under one sun irradiation and highly efficient hydrogen-evolving rate of 3096 µmol g-1 h-1. This work paves a way to explore the improvement of photocatalytic hydrogen production by synergic photothermal effect for potential applications in renewable solar energy utilization and hydrogen production.

Solar Hydrogen Production and Biomass Reforming Using Earth-Abundant Non-Toxic Si-Based Photocatalysts

The efficient production of electrochemical hydrogen and biomass refinement is crucial for the decarbonization of various industries. However, their low efficiency and high energy requirements make them impractical. In this talk, we propose using earth-abundant and non-toxic photocatalysts that can produce hydrogen and reform biomass efficiently by utilizing solar energy. Our approach involves using low bandgap Si flakes (SiF) for efficient light absorption. SiF was further modified with Ni-coordinated N-doped graphene quantum dots (Ni-NGQDs) to enable stable light-driven biomass reforming and hydrogen production. SiF/Ni-NQGDs enabled a record hydrogen productivity and concurrent vanillin production when using kraft lignin as model biomass under simulated sunlight without any buffering agent or sacrificial electron donors. SiF/Ni-NQGDs can also be easily recycled without noticeable performance degradation due to the prevention of Si deactivation through oxidation. Our findings provide valuable insights into the practical application of biomass refinement and electrochemical hydrogen production and efficient use use of solar energy.Reference)1. Y. Choi, S. Choi, I. Lee, T. V. T. Nguyen, S. Bae, J. Ryu, Y. H. Kim, S. Park, J. Ryu, Solar Biomass Reforming and Hydrogen Production with Earth-Abundant Si-Based Photocatalysts. Advanced Materials 2023, Accepted. Figure 1

(Invited) Water Splitting Materials for Solar Thermochemical Hydrogen Production

Solar thermochemical hydrogen (STCH) production uses concentrated sunlight to produce hydrogen using reduction/oxidation of metal oxides. Typically, the metal oxide is heated to high temperature (>1400 oC) causing it to release oxygen, then it is cooled to a lower temperature (<1000 oC) in steam whereby it re-oxidizes, stripping oxygen from water molecules and producing hydrogen. Due to improved stability, non-stoichiometric oxides that do not change phase during the STCH process are typically used, even though the reversible oxygen content is less than phase changing materials. HydroGEN (h2awsm.org) is an Energy Materials Network supported by the U.S. Department of Energy’s Hydrogen and Fuel Cell Technologies Office, and is focused on the development of new water splitting materials for STCH by fostering collaboration between U.S. national laboratories and external entities such as academia and industry. In this presentation, recent progress in developing new water splitting materials led by Sandia National Laboratories (SNL) will be presented. STCH performance of select materials predicted from a defect Graph Neural Network trained on crystal structures derived from density functional theory, subsequently synthesized and characterized using thermogravimetric analysis and flow reactor measurements, will be presented. Additionally, there will be discussion of benchmarking metrics and characterization of exemplar STCH materials. Lastly, trends in water splitting materials and durability considerations and challenges for commercialization will be discussed.SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525

(Invited) High Efficiency, Ultra-Stable Solar Hydrogen Production

Solar water splitting and green hydrogen fuel production has been extensively studied but are confronted with fundamental challenges of simultaneously achieving both high efficiency and long-term stability. In this presentation, I will report on our recent developments of gallium nitride (GaN) based photoelectrochemical and photocatalytic water splitting studies. By growing GaN nanostructures under N-rich conditions, the surfaces can be transformed to be gallium oxynitride during harsh photocatalysis reaction, which not only further protects the surfaces of the light absorber but leads to significantly enhanced photocatalytic and photoelectrochemical performance. Moreover, we have developed unique photocatalytic process wherein high efficiency solar hydrogen can be produced utilizing tap water, or seawater, without any wire connection, or electricity input. The demonstration of large-scale solar water splitting systems and the performance will be discussed and reported.

Simultaneous evaluation of criteria and alternatives method-based site selection for solar hydrogen production plant in Inner Mongolia, China

In the context of achieving carbon neutrality, China's demand for renewable energy continues to grow, with the development of solar energy attracting widespread attention. Aiming at the problem that solar energy is not accessible at all times and the storage of excess power, this paper proposes a model for siting a solar hydrogen plant in Inner Mongolia based on Simultaneous Evaluation of Criteria and Alternatives (SECA). Firstly, considering the uniqueness of solar hydrogen production projects (SHPPs), we incorporate the criteria of hydrogen production capacity and local finance into the siting decision model. Secondly, the SECA method is employed to construct a nonlinear multi-objective optimization model, facilitating the direct determination of criterion weights and enhancing decision-making efficiency. Third, the convergence change of the coefficient β in the SECA method is used to rank the candidate cities by solving the optimization model to produce stable results. Finally, this study verifies the validity of the model used through sensitivity and comparative analyses. The results show that Chifeng is the best location for solar hydrogen production considering the three most important factors are hydrogen production capacity (11.7%), average humidity (12.4%) and average temperature (14.46%).

Artificial Photosynthetic System with Spatial Dual Reduction Site Enabling Enhanced Solar Hydrogen Production.

Although S-scheme artificial photosynthesis shows promise for photocatalytic hydrogen production, traditional methods often overly concentrate on a single reduction site. This limitation results in inadequate redox capability and inefficient charge separation, which hampers the efficiency of the photocatalytic hydrogen evolution reaction. To overcome this limitation, a double S-scheme system is proposed that leverages dual reduction sites, thereby preserving energetic photo-electrons and holes to enhance apparent quantum efficiency. The design features a double S-scheme junction consisting of CdS nanospheres decorated with anatase TiO2 nanoparticles coupled with graphitic C3 N4 . The as-prepared catalyst exhibits a hydrogen evolution rate of 26.84mmolg-1 h-1 and an apparent quantum efficiency of 40.2% at 365 nm. This enhanced photocatalytic hydrogen evolution is ascribed to the efficient charge separation and transport induced by the double S-scheme. Both theoretical calculations and comprehensive spectroscopy tests (both insitu and exsitu) affirm the efficient charge transport across the catalyst interface. Moreover, substituting the reduction-type catalyst CdS with other similar sulfides like ZnIn2 S4 , ZnS, MoS2 and In2 S3 further confirms the feasibility of the proposed double S-scheme configuration. The findings provide a pathway to designing more effective double S-scheme artificial photosynthetic systems, opening up fresh perspectives in enhancing photocatalytic hydrogen evolution performance.

Photocatalytic water splitting properties of GeC/InS van der Waals heterostructure: first-principles calculations

Based on first-principles, we conducted an in-depth study of the GeC/InS van der Waals heterostructure formed by GeC and InS and discussed its structure, electronic properties and optical properties. First, we observe that this heterostructure has negative binding energy, indicating that the interlayer interactions are mainly affected by van der Waals forces. Through band structure and density of state analysis, we confirmed its type-II band alignment characteristics, which means that photogenerated carriers have the ability to automatically separate in space. Moreover, the average charge density difference and Bader charge analysis show that there is a built-in electric field in the heterostructure, and further proves that GeC/InS forms a Z-scheme charge transfer mechanism. Interestingly, the band edge position spans the water redox potential and can fully induce the redox reaction of water splitting, indicating that it is a potential photocatalyst. The high light absorption coefficient shown in the absorption spectrum also further confirms its excellent photocatalytic activity. The most striking thing is that the solar hydrogen production efficiency of GeC/InS heterostructure is as high as 44.39%. Our research demonstrates the theoretical basis for GeC/InS heterostructure as a photocatalyst.

Research on Hydrogen Production System Technology Based on Photovoltaic-Photothermal Coupling Electrolyzer

Solar hydrogen production technology is a key technology for building a clean, low-carbon, safe, and efficient energy system. At present, the intermittency and volatility of renewable energy have caused a lot of “wind and light”. By combining renewable energy with electrolytic water technology to produce high-purity hydrogen and oxygen, which can be converted into electricity, the utilization rate of renewable energy can be effectively improved, while helping to improve the solar hydrogen production system. This paper summarizes and analyzes the research status and development direction of solar hydrogen production technology from three aspects. Energy supply mode: the role of solar PV systems and PT systems in this technology is analyzed. System control: the key technology and system structure of different types of electrolytic cells are introduced in detail. System economy: the economy and improvement measures of electrolytic cells are analyzed from the perspectives of cost, consumption, efficiency, and durability. Finally, the development prospects of solar hydrogen production systems in China are summarized and anticipated. This article reviews the current research status of photovoltaic-photothermal coupled electrolysis cell systems, fills the current research gap, and provides theoretical reference for the further development of solar hydrogen production systems.

Noble metal-free 0D-1D CoOx/Mn0.3Cd0.7S nanocomposites for efficient visible-light hydrogen production

Here, a series of MnxCd1-xS sosoloid composite photocatalysts with visible-light activity were first prepared by a solvothermal process. The element ratio of Cd2+ to Mn2+ was optimized to be Mn0.3Cd0.7S in MnxCd1-xS sosoloid on account of its photocatalytic activity for H2 evolution from H2O in response to visible light excitation. And on this basis, the CoOx nanopariticles were loaded on the surface of Mn0.3Cd0.7S sosoloid composite to obtain a binary p-n heterojunction of CoOx/Mn0.3Cd0.7S composite through a facile impregnation process and a high temperature sintering procedure. Benefitting from the synergistic effect of the built-in electric field, binary p-n heterojunction structure, and rearrange of the Fermi level equilibrium, the as-synthesized CoOx/Mn0.3Cd0.7S composite presents a highly enhanced photocatalytic activity for hydrogen production from H2O in response to visible light excitation, which is demonstrated to be 53.4 and 4.0 times higher than that of the primitive CdS and Mn0.3Cd0.7S, respectively. Furthermore, after 4 times circles of photocatalytic H2 production tests, the CoOx/Mn0.3Cd0.7S composite still keeps 92.0 % of the original photocatalytic activity. Considering its reasonable photochemistry stability and excellent photocatalytic activity for hydrogen evolution from H2O under with visible light excitation, the as-synthesized CoOx/Mn0.3Cd0.7S composite has potential applications in solar hydrogen production areas.

Efficient and Stable Tin–Lead Perovskite Photoconversion Devices Using Dual‐Functional Cathode Interlayer

AbstractTin–lead halide perovskites (TLHPs) are promising photoactive materials for photovoltaics (PVs) due to reduced toxicity and broad light absorption. However, their inherent ionic vacancies facilitate inward metal diffusion, accelerating device degradation. Here, efficient, stable TLHP‐based PV and photoelectrochemical (PEC) devices are reported containing a chemically protective cathode interlayer—amine‐functionalized perylene diimide (PDINN). Solution‐processed PDINN effectively extract electrons and suppress inward‐metal diffusion by forming tridentate metal complexes with its nucleophilic sites. The PV device achieved an efficiency of 23.21% (&gt;81% retention after 750 h at 60 °C and &gt;90% retention after 3100 h at 23 ± 4 °C), and the first demonstration of TLHP‐based PEC devices exhibit a record‐high bias‐free solar hydrogen production rate (33.0 mA cm−2; ≈3.42 × 10−6 kg s−1 m−2) when coupled with biomass oxidation, which is ≈1.7‐fold higher than the ultimate target set by the U.S. Department of Energy for one‐sun hydrogen production. These findings demonstrate the potential of TLHPs for efficient, stable photoconversion by the molecular design of the cathode interlayer.

S-scheme heterojunction and dual co-catalysts on carbonized paper for biphase interface photocatalytic hydrogen production from water

Solar-driven water splitting by photocatalysts is considered a cost-effective and environmental-friendly way to produce hydrogen fuel. However, the efficiency of hydrogen production in photocatalysis systems is still low due to the inefficient light absorption, photogenerated carrier recombination, and sluggish reaction kinetics. Here, we design and synthesize a composite carbonized paper with Co3O4/Fe2O3/g-C3N4/Au loaded on carbonized fiber (CF) by layer-by-layer assembly. Fe2O3 and g-C3N4 form an S-scheme heterojunction for enhanced interfacial charge separation. The spatially separated Co3O4 and Au co-catalysts capture photogenerated carriers and inhibit surface recombination for enhancing oxidation and reduction kinetics. In addition, composite carbonized paper floats on the water surface to form a solid-gas biphase photocatalytic interface (photothermal-generated steam/composite carbonized paper/hydrogen) with the help of the photothermal effect of composite carbonized paper. This biphase photocatalytic interface effectively reduces the transmission resistance of hydrogen and the adsorption barrier of water molecules. The CF/Co3O4/Fe2O3/g-C3N4/Au composite paper exhibits an impressive hydrogen production rate up to 78,561.51 μmol h−1 g−1. Stable loading of Co3O4/Fe2O3/g-C3N4/Au in composite paper contributes to the photocatalytic cycle. The hydrogen evolution rate in the third cycle remains 96.5 %. This work demonstrates that the combination of S-scheme heterojunction, spatially separated co-catalysts, and biphase photocatalytic interface can be a promising strategy for efficient photocatalytic platforms for solar hydrogen production.

In Situ Preparation of 0D/2D Zn-Ag-In-S Quantum Dots/RGO Heterojunctions for Efficient Photocatalytic Hydrogen Production

The creation of junctions between 0D and 2D materials can be an efficient strategy to enhance charge separation for solar hydrogen production. In this study, a simple in situ growth method has been used to synthesize a series of 0D/2D Zn-Ag-In-S quantum dots/reduced graphene oxide (ZAIS QDs/RGO) heterojunctions. The developed heterojunctions were characterized for structural characteristics, morphology, and photocatalytic performance, while varying the content of RGO. We observed that photocatalytic hydrogen production reached a maximum at an RGO content of 30 μL (342.34 µmol g−1 h−1), surpassing that of pure ZAIS QDs (110.38 µmol g−1 h−1) by 3.1 times, while maintaining excellent stability. To understand this enhancement, we performed time-resolved fluorescence and electrochemical impedance spectroscopy. The fluorescence lifetime of RGO loaded at 30 μL (417.76 ns) was significantly higher than that of pure ZAIS QDs (294.10 ns) and had the fastest charge transfer, which can be attributed to the charge transfer and storage capacity of RGO to extend the lifetime of photogenerated carriers and improve the charge separation efficiency. This study offers a simple synthesis method for constructing 0D/2D QDs/RGO heterojunction structures and provides a valuable reference for further enhancing the activity and stability of I-III-VI sulfide QDs.

Boosting solar photothermal synergy for efficient overall water splitting based on Mg, Al codoped and Rh/Cr2O3/CoOOH coloaded SrTiO3

The synergistic coupling of light and heat in solar energy has attracted increasing research attention. In this work, both codoping and coloading were applied to SrTiO3-based catalysts to improve their solar photo and thermal conversion, respectively, and maximum productivities of 51.55 and 25.59 mmol·g−1·h−1 were achieved for H2 and O2 in photothermal synergistic water splitting. The yield of H2 was nearly double that achieved via pure photocatalysis. In addition to many experiments and characterizations, DFT calculations were also performed to clarify the photothermal synergy. It was found that both the light absorbance and mobility of photoinduced carriers could be promoted by solar thermal effects in the material. Meanwhile, the energy barriers of the key steps were reduced with increasing temperature in the hydrogen production driven by solar photo effects. This work offers new ideas for designing catalysts for solar hydrogen production with photothermal synergistic strategies.

Numerical simulation and performance analysis of solar hydrogen production using anion exchange membrane electrolyzer and blending with natural gas

Hydrogen production using solar energy and blending in a natural gas pipeline is a cost-effective alternative to hydrogen storage and transmission that leads to lower CO2 emissions caused by the energy infrastructure. In this paper, energy, exergy, and Exergoeconomic analyses of a solar hydrogen production system and its blending with natural gas in a city gate station of Isfahan city are performed in three days with minimum, average, and maximum solar irradiations. The system includes photovoltaic arrays, anion exchange membrane electrolyzer cells (AEMECs), a hydrogen compressor, and a system blending. The AEMEC is used due to its less expensive catalysts, non-acidic electrolyte, and high efficiency at high pressures. A three-dimensional numerical model is developed to determine the AEMEC’s polarization curve, accurately. The results show that with increasing solar irradiation and decreasing ambient temperature, the maximum power of the PV increases and the energy and exergy efficiency of the PV decreases. By increasing the injection of hydrogen into natural gas from 1% to 10% vol., the lower heating value of the fuel and the Wobbe Index decrease by 6% and 1.55%, respectively. By injection of 10% vol. hydrogen gas into natural gas compared to the case of using natural gas without hydrogen, the exergy cost of natural gas blended with hydrogen increases by 5.9%. Considering the environmental benefits of using hydrogen in combination with natural gas, including the reduction of greenhouse gases, and the fact that blending hydrogen up to 10% vol. with natural gas does not require any change in urban gas supply facilities, this process is feasible. In the case of using high-pressure AEMEC and removing the compressor to produce hydrogen at high pressure, the exergy cost of high-pressure hydrogen reduces by 29.3%.

Single-Site Ni-Grafted TiO2 with Diverse Coordination Environments for Visible-Light Hydrogen Production.

Solar hydrogen production at a high efficiency holds the significant importance in the age of energy crisis, while the micro-environment manipulation of active sites on photocatalysts plays a profound role in enhancing the catalytic performance. In this work, a series of well-defined single-site Ni-grafted TiO2 photocatalysts with unique and specific coordination environments, 2,2'-bipyridine-Ni-O-TiO2 (T-Ni Bpy) and 2-Phenylpyridine-Ni-O-TiO2 (T-Ni Phpy), were constructed with the methods of surface organometallic chemistry combined with surface ligand exchange for visible-light-induced photocatalytic hydrogen evolution reaction (HER). A prominent rate of 33.82 μmol ⋅ g-1 ⋅ h-1 and a turnover frequency of 0.451 h-1 for Ni are achieved over the optimal catalyst T-Ni Bpy for HER, 260-fold higher than those of Ni-O-TiO2 . Fewer electrons trapped oxygen vacancies and a larger portion of long-lived photogenerated electrons (>3 ns, ~52.9 %), which were demonstrated by the electron paramagnetic resonance and femtosecond transient IR absorption, correspond to the photocatalytic HER activity over the T-Ni Bpy. The number of long-lived free electrons injected from the Ni photoabsorber to the conduction band of TiO2 is one of the determining factors for achieving the excellent HER activity.

Scaling up BiVO4 Photoanodes on Porous Ti Transport Layers for Solar Hydrogen Production.

Commercialization of photoelectrochemical (PEC) water-splitting devices requires the development of large-area, low-cost photoanodes with high efficiency and photostability. Herein, we address these challenges by using scalable fabrication techniques and porous transport layer (PTLs) electrode supports. We demonstrate the deposition of W-doped BiVO4 on Ti PTLs using successive-ionic-layer-adsorption-and-reaction methods followed by boron treatment and chemical bath deposition of NiFeOOH co-catalyst. The use of PTLs that facilitate efficient mass and charge transfer allowed the scaling of the photoanodes (100 cm2 ) while maintaining ~90 % of the performance obtained with 1 cm2 photoanodes for oxygen evolution reaction, that is, 2.10 mA cm-2 at 1.23 V vs. RHE. This is the highest reported performance to date. Integration with a polycrystalline Si PV cell leads to bias-free water splitting with a stable photocurrent of 208 mA for 6 h and 2.2 % solar-to-hydrogen efficiency. Our findings highlight the importance of photoelectrode design towards scalable PEC device development.

Techno-economic analysis of solar hydrogen production via PV power/concentrated solar heat driven solid oxide electrolysis with electrical/thermal energy storage

Techno-economic analysis of solar hydrogen production via PV power/concentrated solar heat driven solid oxide electrolysis with electrical/thermal energy storage