Photoelectrochemical Reactor Research Articles

A Reactor based on P‐N Heterojunction of Polypyrrole and Porous Silicon for Photocatalytic and Electro‐assisted Photocatalytic Performance

AbstractIn this work, a photoelectrochemical reactor with an anode based on hybrid structure between conducting polymer polypyrrole (PPy) and porous silicon (PSi) was fabricated and utilized to evaluate the photocatalysis and electro‐assisted photocatalysis for degradation of rhodamine B (RhB) solution. The PSi was made of n‐type silicon single‐crystal wafer by the metal‐assisted chemical etching (MACE). The anode PPy/PSi formed following a polymerization of the PPy on the PSi from the vapour‐phase route using oxidant FeCl3. Typical material characterizations of the PPy, PSi and PPy/PSi were investigated via scanning electron microscope (SEM), and spectroscopies of Fourier‐transform infrared (FTIR), Raman scattering and UV‐vis. Under visible light radiation (halogen light with the wavelength region of 400–700 nm), photocatalytic and electro‐assisted photocatalytic processes of the reactor were conducted by degradation of the RhB solution. A heterojunction (p‐n) of the PPy/PSi was proposed to explain the efficient catalytic performance of the reactor.

A coupled faradaic/electrostatic boosting strategy for decolorization of a refractory dye inside a dually-biased photoelectrochemical reactor: Time and energy saving

A green sustainable strategy for environmental remediation and treatment of dye-polluted water is the application/development of effective photoelectrochemical (PEC) reactors. Despite some recent progress in PEC systems, achieving a complete decolorization is still a challenging issue and often requires a long period of reactor operation. Herein, the authors address this interesting time/energy-related problem, demonstrating how without consuming extra electricity/chemicals, fabricating complex photoelectrodes, or changing the pH of medium, one can effortlessly promote the activity of a PEC reactor just by its coupling to a non-faradaic bias source. By applying this novel dually biased (faradaic/electrostatic) boosting strategy, we reveal that decolorization of methyl orange (a refractory dye pollutant) is significantly improved and the decolorization time (thereby energy consumption) is reduced by almost half in comparison to that of a conventional PEC reactor–operating under a single-bias (faradaic) condition. The reactor activity and its photoelectrochemical response are finally discussed in detail in terms of applied potential biases, semiconductor's band bending, open-circuit-potential displacement, electrostatic interaction and electrosorption of dye pollutant.

CFD modeling and simulation of benzyl alcohol oxidation coupled with hydrogen production in a continuous-flow photoelectrochemical reactor

Various conversion routes of biomass and its derivative compounds into high-value products has attracted attention from researchers recently. Among these, a solar-driven photoelectrochemical (PEC) oxidation approach of biomass alcohols to aldehydes is particularly of great interest for the potential applications because the reaction is selective and simultaneously accompanied with hydrogen production. Here, we propose a simulation of selective oxidation of benzyl alcohol into benzaldehyde coupled with hydrogen production in a 2-dimensional continuous-flow PEC reactor using COMSOL Multiphysics (5.6). In order to develop and fabricate a simple yet efficient reactor for a practical use, it is crucial to investigate the effects of operating and design parameters of the reactor on the reactions. Our studies demonstrated that the main contributions to product formation were the electrolyte flow velocity and the width of electrolyte channels. The optimized design parameter exhibited good photoelectrochemical performance with uniform potential distribution within the channels which served diffusion of neutral and charged species and electrochemical reaction. The maximum conversion of benzyl alcohol in this work was 48.25% with 100% selectivity of benzaldehyde. These findings are key for the design of the continuous-flow PEC reactor that can be applied to any series of biomass conversion reactions under mild conditions.

The design and characterisation of a Z-scheme Bi2O2S/ZnO heterojunction photoanode for the photoelectrochemical removal of ciprofloxacin in synthetic and real wastewater

Towards the engineering of semiconductors for improved visible light photoelectrochemical degradation of organic pollutants in wastewater, we present the preparation of a Z-scheme heterojunction of Bi2O2S and ZnO nanoparticles for the removal of ciprofloxacin from wastewater. The Bi2O2S/ZnO nanocomposite heterojunction was synthesised via an in-situ hydrothermal method and deposited on FTO substrate to form the photoanode. The semiconductors and the photoanodes were characterised with electron microscopy, XRD, photo-electrochemistry, photoluminescence, XPS and UV/Vis diffusive reflectance techniques. The degradation of ciprofloxacin was enhanced by the heterojunction in comparison with the Bi2O2S and ZnO photoanodes. We attribute the enhanced performance to the presence of an internal electric field (IEF), the low rate of recombination of photogenerated electrons and holes, lower charge transfer resistance, and high photocurrent density of the heterojunction based on data from photoluminescence, electrochemical impedance spectroscopy, XPS, and photocurrent response. The extent of mineralisation of ciprofloxacin was calculated as 86 % from total organic carbon (TOC) measurement. LC-MS analysis provided the degradation pathway and premise for the reaction scheme, while quantitative structure–activity relationship (QSAR) model was used to predict the toxicity of the intermediate and by-product. The Bi2O2S/ZnO photoanode was stable after seven treatment cycles. The photoelectrochemical reactor was used in the treatment of ciprofloxacin in real wastewater with 87 % TOC removal. Thus, the paper reveals the performance of a unique Z scheme band gap engineering of semiconductors for application in the removal of pharmaceuticals in wastewater.

Technoeconomic analysis of photoelectrochemical hydrogen production from desalination waste brine using concentrated solar flux

Co-generation of hydrogen with value-added by-products is a promising route for affordable low-carbon hydrogen. This work presents a system for and a technoeconomic analysis of hydrogen with the co-generation of chlorine and sodium hydroxide from waste brine. The system uses a conceptual triple-junction gallium arsenide (3-J GaAs)-based photoelectrochemical (PEC) reactor at high solar concentrations (50–500x). The base case of 200x solar concentration results in a solar-to-chemical (SCE) efficiency of 15% and a levelized cost of hydrogen (LCOH) production of $15.76/kgH2. Revenue from by-products ($45.36/kgH2) is critical for offsetting the operating costs, with sodium hydroxide constituting 64% of total by-product revenue. The sensitivity analysis showed that under favorable combinations of the key variables (sodium hydroxide price, waste brine pretreatment price, and PEC replacement lifetime) PEC hydrogen generation from waste brine would be viable and have prices reaching $0.78/kgH2.

Novel photoelectrochemical 3D-system for water disinfection by deposition of modified carbon nitride on vitreous carbon foam

Graphitic carbon nitride (GCN) is an optical semiconductor with excellent photoactivity under visible light irradiation. It has been widely applied for organic micropollutant removal from contaminated water, and less investigated for microorganisms’ inactivation. The photocatalytic degradation mechanism using GCN is attributed to a series of reactions with reactive oxygen species and photogenerated holes that can be boosted by modifying its physical-chemical structure. This work reports a successful improvement of the overall photocatalytic and electrocatalytic activities of the pristine material by thermal and chemical modification by a copolymerisation synthesis method. The copolymerisation of dicyandiamide as a precursor with barbituric acid strongly reduced photoluminescence due to the enhanced charge separation thus improving the catalyst efficiency under visible light irradiation. The material with 1.6 wt% of barbituric acid showed the best photocatalytic performance and electrochemical properties. This photocatalyst was selected for immobilisation on a conductive carbon foam, which promotes a higher electrochemical active surface area and enhanced mass transfer. This three-dimensional metal-free electrode was employed for the photoelectrochemical inactivation of two different microorganisms, Escherichia coli, and Enterococcus faecalis, obtaining removals below the detection limit after 30 min in simulated faecal-contaminated waters. This photoelectrochemical reactor was also applied to treat polluted river and urban waste waters, and the faecal contamination indicators were vastly reduced to values below the detection limit in 60 min in both cases, showing the wide applicability of this innovative photoelectrode for different types of polluted aqueous matrices.

Development of a new photoelectrochemical system for clean hydrogen production and a comparative environmental impact assessment with other production methods

Hydrogen is recognized as a critical substance for diversifying the global energy supply, providing new economic opportunities and realizing a carbon-free energy sector. In the current study, a life cycle assessment is conducted on a photoelectrochemical hydrogen production process of a newly developed photoelectrochemical reactor. With a photoactive electrode area of 870 cm2, the hydrogen production rate of the reactor is 47.1 μg/s while operating with the energy and exergy efficiencies of 6.3% and 6.31%, respectively. For a Faradaic efficiency of 96%, the produced current density is evaluated as 3.15 mA/cm2. A comprehensive study is conducted for a cradle-to-gate life cycle assessment of the proposed hydrogen photoelectrochemical production system. The life cycle assessment results of the proposed photoelectrochemical system are further evaluated within a comparative analysis by considering a total of four key hydrogen generation processes, namely steam-methane reforming, photovoltaics-based and wind electricity-driven proton exchange membrane water electrolysis and the current photoelectrochemical system and studying five environmental impact categories. The global warming potential of hydrogen production via the proposed photoelectrochemical cell is evaluated as 1.052 kg CO2 equivalent per kg of produced hydrogen. In the normalized comparative life cycle assessment results, the PEC-based hydrogen production is found to be the most nature-friendly option among the considered pathways.

Development and evaluation of a solar based integrated hydrogen energy system for mobile applications

Sustainable and nature-friendly energy systems are critical in playing a key role in meeting the needs for better energy security and reduced environmental impacts which appear among the primary concerns of today’s modern society in the 21st century. The present study, in this regard, undertakes the development and thermodynamic investigation of a unique solar energy-based multigenerational energy system for modular and transportable applications. Electricity, heat, hot water, hydrogen and clean water are the useful commodities generated by this uniquely integrated energy system. This system employs a photoelectrochemical reactor stack for wastewater treatment and hydrogen production. The hydrogen generated from the photoelectrochemical water splitting process is employed within a proton exchange membrane fuel cell providing electricity and heat for hot water. The system’s energetic and exergetic efficiencies under different operational conditions are investigated and comparatively evaluated. The key effects of varying prime operational conditions and state properties on the system performance and hence the efficiency, as considered in the system analysis, are parametrically investigated, and the obtained results are comprehensively discussed along with explanations about the main drivers. The integrated system provides 1.026 kW electrical power along with, 2.1 kW space heating, 0.6 kW heat for hot water, and hydrogen and clean water production rates of 22.97 mg/s and 9.79 g/s, respectively. An overall energy efficiency of 16.79 % and an overall exergy efficiency of 17.31 % are obtained and discussed. The presently developed system is capable of operating as a self-standing system in an off-grid manner. Furthermore, the number of PEC reactors required to sustain the system needs to be maintained, which can be achieved by potential improvement in PEC water splitting process.

SO2 pollutant conversion to sulfuric acid inside a stand-alone photoelectrochemical reactor: A novel, green, and safe strategy for H2SO4 photosynthesis

Instead of performing the risky gas-phase oxidization of SO2, to produce sulfuric acid, this noxious gas can be first dissolved in water and then the resulting sulfite (SO32-) anions could be safely oxidized through a green photoelectrochemical route upon an environmentally-friendly, affordable photoanode. In this article, the authors deal with this environmentally/industrially important issue and conduct the sulfite-to-sulfate conversion process upon an n-type semiconducting hematite thin-film, deposited electrochemically on a commercially available tin-oxide substrate. The investigations revealed an excellent photoelectrochemical response and a fair oxidizing ability for the fabricated photodevice/reactor, to convert sulfite to sulfate in a two-electrodic standalone setup [no external potential was applied]. Furthermore, a superior activity was achieved for the production of sulfate upon the Co (II) impregnated photoanode. By drawing the system's energy diagram and noticing the reactions which occur during the photoconversion process, the phenomenon was also interpreted from a physicoelectrochemical mechanistic perspective.

Computational fluid dynamics simulation of bubble hydrodynamics in water splitting: Effect of electrolyte inflow velocity and electrode morphology on cell performance

Efficient management of oxygen gas bubbles evolving at the photoanode is important for a good overall performance of a photoelectrochemical (PEC) cell. The process of formation, detachment, coalescence and rise affects the bubble residence time at or near the photoanode. A reduced bubble residence time promotes easier electrolyte access to the photoanode surface, thereby enhancing the oxygen evolution reaction (OER) kinetics. In this work, computational fluid dynamics (CFD) simulations using laminar flow and phase-field model in COMSOL Multiphysics are conducted to study the gas bubble hydrodynamics for different bubble configurations, sizes, and bubble gaps. CFD results predict enhanced bubble rise in the presence of forced convection, i.e., some electrolyte inflow velocity (u≠0m.s−1). Experimental results using hematite as the model electrode also show a higher photocurrent density (ca. 4.33 mA.cm−2 at 2 V vs. RHE) for u = 0.1 m.s−1, compared to that without flow (3.5 mA.cm−2 at 2 V vs. RHE). This indicates improved access of electrolyte at the electrode surface and faster OER. Further, CFD simulations for electrode morphology effects show a reduced bubble adhesion for hydrophilic hematite nanorod arrays compared to planar photoanode, due to capillary wicking. The continuous contact film detaches and results in a reduced blockage of active sites at the bubble base, thereby enhancing the PEC performance for the nanorod arrayed morphology. Here too, experimental results show a four-fold increase in photocurrent density (ca. 0.1 mA.cm−2 at 1.5 V vs. RHE) and a 210 mV cathodic shift in onset potential for nanorods, compared to planar electrodes (0.025 mA.cm−2 at 1.5 V vs. RHE). A significant reduction in charge transfer resistance is observed for the former, implying better OER kinetics. The results obtained help in the understanding of transient processes involving O2 bubble hydrodynamics and electrolyte usage efficiency in a PEC reactor.

Design and experimental investigation of a new photoelectrochemical reactor for green hydrogen production

The current study undertakes the development, experimental testing and performance evaluation of a new photoelectrochemical reactor for green hydrogen production. The reactor is uniquely designed to utilize the available solar light more effectively. A copper oxide photocathode fabricated by the electrodeposition technique is employed as a photoelectrode in the reactor. As a counter electrode, the reactor comprises a titanium dioxide-coated electrode offering high stability in the presence of moisture and corrosive media. The electrochemical tests of the reactor are experimentally conducted for various conditions to better evaluate the performance, including with light and without light conditions. In this regard, both energy and exergy efficiencies of the present reactor for hydrogen production rates are evaluated under various operating conditions. The results of the current study show that the highest hydrogen production rate from the reactor is found to be 0.62 µg/s with a solar irradiation intensity of 600 W/m2 and an applied voltage of 2.0 V and that the present reactor achieves an energy efficiency of 0.193% and an exergy efficiency of 0.196% under these conditions.

New Photoelectrochemical Reactor for Hydrogen Generation: Experimental Investigation

In the scope of this study, a new photoelectrochemical (PEC) reactor, comprising a novel geometry for effective absorption of sunlight, is developed conceptually, and tested and assessed experimentally. The conic mesh structure of the photoelectrode offers maximizing the performance via passive tracking of solar light during daylight. In sequence, electrodeposition and sol–gel dip coating techniques are practiced, fabricating a copper oxide semiconductor as a working electrode and a titanium dioxide-coated electrode as the counter electrode. The new reactor concept is experimentally assessed for various conditions through electrochemical tests including open circuit potential, linear sweep voltammetry, cyclic voltammetry, and PWR potentiostatic tests. Energy and exergy efficiencies and hydrogen production rates are evaluated for various experimental conditions implying with and without light. The highest hydrogen production rate corresponding to 4.48 μg H2/s at near-atmospheric conditions (25 °C temperature and 101.3 kPa pressure) is obtained with the applied external bias of 2.25 V, where the reactor operates under artificial solar light with an intensity of 1000 W/m2. The produced photocurrent density is determined to be 1.81 mA/cm2, corresponding to a photo-conversion efficiency of 1.84%. For these operational conditions, the energetic and exergetic efficiencies of the reactor are evaluated as 0.866 and 0.878%, respectively. Without light case, the PEC reactor acting as an electrolyzer operates with energetic and exergetic electrolysis efficiencies of 56.51 and 54.38%, respectively.

A photoelectrochemical reactor for ion separation and hydrogen production

Global water demand has been rising rapidly due to increased industrial activities and personal consumption. The regulations and restrictions specifically introduced to achieve sustainable environmental targets have pushed the industry to adopt effective treatment methods to reuse the wastewater streams accordingly. For this reason, developing such systems that can produce reusable and useful by-products is important along with wastewater treatment. Accordingly, a photoelectrochemical reactor is designed and studied for the treatment of textile wastewaters and reclamation of sodium hydroxide. The presently designed reactor combines some of the aspects of photoelectrochemical cells and electrodialysis process. Various potentials are considered and applied to the reactor to investigate the hydrogen production rates and efficiencies of the reactor. The conductivity removal efficiencies are then found to be 37%, 39%, 55%, 66%, 87% while the color removal efficiencies are 96%, 95%, 91%, 75%, 74% for 1.7, 1.9, 2.1, 2.3 and 2.5 V, respectively. Furthermore, the hydrogen production rates for illuminated studies are measured as 0.024, 0.041, 0.061, 0.170, 0.302 mmol/h, respectively.

A New Photoelectrochemical Reactor with Special Photocathode Design for Hydrogen Production

Both electrodeposition and performance assessment of new photocathode design are carried out using cuprous oxide for solar hydrogen production. The maximum delivered light can be collected using the mesh dome design of the photocathode, and the light can also reach the farthest photocathode surfaces via the mesh shape. The stainless‐steel mesh dome electrode is coated with cuprous oxide using the electrodeposition method. This photocathode is examined in an alkaline electrolyte solution of potassium dioxide for hydrogen production. Two light angles are studied to explore the effects of the new photocathode design on the hydrogen yield rate and associated energy and exergy system efficiencies during the daytime, where the light angles change. The maximum hydrogen production rates are generated experimentally at 0.1 m KOH at the 45° tilt light, and vertical light positions are 5.13 and 5.58 μg s−1, respectively. Moreover, the highest exergy and energy system efficiencies are 0.82% and 1.18%, respectively, under vertical light, while they are 0.75% and 1.09% under tilted light conditions. The improvement of hydrogen production rates at tilted light can reach around 75.6% of the enhancement by vertical light due to the new photocathode design.

A new photoelectrochemical reactor designed for solar hydrogen fuel production: Experimental study

A novel photoanode configuration of meshy type dome design is examined to exploit the maximum accessible light during available sun time at any solar rays angle due to its unique structure. This photoanode shape aims to receive the maximum light quantity by utilizing the possible illumination area. Also, the meshy design lets the solar ray spread into the body of the dome photoanode at any solar rays angle. Titanium dioxide is prepared to coat the stainless steel photoanode using the sol–gel dip-coating method. Two concentrations of potassium dioxide solution are used to study the electrolyte solution conductivity effects on the hydrogen production rate and the associated energy and exergy efficiencies. The vertical and tilted light boundaries are studied to evaluate the enhancement of the hydrogen production rate and the corresponding system efficiencies due to the new dome mesh photoanode design. The present experimental results indicate that increasing the solution concentration significantly affects the hydrogen production rates and associated system efficiencies. The greatest hydrogen mass production rates produced at 0.25 M KOH under artificial tilted (45°) and vertical light boundaries are 31.55 µg/s and 32.22 µg/s, respectively. The overall energy and exergy system efficiencies can be reached to be 5.98% and 4.08% under vertical light, while it is 5.89% and 4.02% at tilted light boundaries. The development of the hydrogen production rate obtained at artificial tilted light boundaries changes between 74% and 80% compared to the enhancement which occurred at vertical artificial light boundaries.

En Route to a Unified Model for Photoelectrochemical Reactor Optimization. II–Geometric Optimization of Perforated Photoelectrodes

Results have been reported previously of a model describing the performance of photoelectrochemical reactors, which utilize semiconductor | liquid junctions. This model was developed and verified using SnIV-doped α-Fe2O3 as photoanodes. Hematite films were fully characterized to obtain parameter inputs to a model predicting photocurrent densities. Thus, measured photocurrents were described and validated by the model in terms of measurable quantities. The complete reactor model, developed in COMSOL Multiphysics, accounted for gas evolution and desorption in the system. Hydrogen fluxes, charge yields and gas collection efficiencies in a photoelectrochemical reactor were estimated, revealing a critical need for geometric optimization to minimize H2-O2 product recombination as well as undesirable spatial distributions of current densities and “overpotentials” across the electrodes. Herein, the model was implemented in a 3D geometry and validated using solid and perforated 0.1 × 0.1 m2 planar photoanodes in an up-scaled photoelectrochemical reactor of 2 dm3. The same model was then applied to a set of simulated electrode geometries and electrode configurations to identify the electrode design that would maximize current densities and H2 fluxes. The electrode geometry was modified by introducing circular perforations of different sizes, relative separations and arrangements into an otherwise solid planar sheet for the purpose of providing ionic shortcuts. We report the simulated effects of electrode thickness and the presence or absence of a membrane to separate oxygen and hydrogen gases. In a reactor incorporating a membrane and a photoanode at 1.51 V vs RHE and pH 13.6, an optimized hydrogen flux was predicted for a perforation geometry with a separation-to-diameter ratio of 4.5 ± 0.5; the optimal perforation diameter was 50 µm. For reactors without a membrane, this ratio was 6.5 and 8.5 for a photoanode in a “wired” (monopolar) and “wireless” (photo-bipolar) design, respectively. The results and methodologies presented here will serve as a framework to optimize composite photoelectrodes (semiconductor | membrane | electrolyte), and photoelectrochemical reactors in general, for the production of hydrogen (and oxygen) from water using solar energy.

Innovative design of a continuous flow photoelectrochemical reactor: Hydraulic design, CFD simulation and prototyping

Photochemical (PC) and photoelectrochemical (PEC) techniques have being proven fruitful for environmental remediation, including the removal of organic emerging contaminants from water and wastewater, besides to be able to work as disinfection process. However, the majority of PEC reactors still remain in lab-scale and advances in the reactors’ design and optimization is required to achieve exploitation and practical application. In order to contribute to this area of research, this study aimed to develop an innovative design of a PC/PEC system. A designed 3-D honeycomb-type photoanode resulted in reactive area 4.8 times higher when compared to cylindrical reactors. Computational fluid dynamic (CFD) simulations were performed using CFX software. Reynolds number has shown turbulent regime well defined from a flow rate of 1000 L.h−1. A polyamide prototype was manufactured by a 3D-printer and hydraulic bench-tests were performed. The model adopted for the CFD simulations was validated by comparing calculations, bench-tests and simulation results. During validation process, differences varied between 1.84% and 5.06% for the total pressure and Reynolds, respectively, in the upstream flow chamber working at 1000 L.h−1. The design presented can provide scale-up due to it high modularity and be built in metallic electrodes mostly that layered by photo-responsive oxides, besides allowing the use of non-immobilized photocatalysts or just like for electrolytic treatment. Additionally, allow use of different UV sources (i.e. UV-LED, Xenon, Mercury lamps), improved mixing and adequate flow distribution.

(Invited) A Stable Integrated Photoelectrochemical Reactor for Hydrogen Production from Water

Among the major challenges in solar water, splitting to molecular hydrogen and oxygen is making a stable and affordable system for largescale applications. In this work we present results of the design, fabrication, and testing a photoelectrochemical reactor composed of the following. 1) An integrated device to reduce the balance of the system cost. 2) A concentrated sunlight to reduce the photoabsorber cost. 3) An alkaline electrolyte to reduce catalyst cost and eliminate external thermal management needs. The system consists of an III-V-based photovoltaic cell integrated with Ni foil as catalyst for oxygen production that also protects the cell from corrosion. At low light concentration and without the use of optical lenses, the solar-to-hydrogen (STH) efficiency was found to be 18.3%, while at high light concentration (up to 207 suns) with the use of optical lenses, the STH efficiency was 13%. Catalytic tests conducted for over 100 hours at 100–200 suns showed no sign of degradation nor deviation from product stoichiometry (H2/O2=2). Further tests projected a system stability of over nine years. Figure 1

Benchmarking of oxygen evolution catalysts on porous nickel supports

Summary Active and inexpensive oxygen evolution reaction (OER) electrocatalysts are needed for energy-efficient electrolysis applications. Objective comparison between OER catalysts has been blurred by the use of different supports and methods to evaluate performance. Here, we selected nine highly active transition-metal-based catalysts and described their synthesis, using a porous nickel foam and a new Ni-based dendritic material as the supports. We designed a standardized protocol to characterize and compare the catalysts in terms of structure, activity, density of active sites, and stability. NiFeSe- and CoFeSe-derived oxides showed the highest activities on our dendritic support, with low overpotentials of η100 ≈ 247 mV at 100 mA cm–2 in 1 M KOH. Stability evaluation showed no surface leaching for 8 h of electrolysis. This work highlights the most active anode materials and provides an easy way to increase the geometric current density of a catalyst by tuning the porosity of its support.

Multi-component modeling and simulation of a new photoelectrochemical reactor design for clean hydrogen production

A novel photoelectrochemical cell design to make a unique reactor is developed and investigated to improve solar to hydrogen conversion efficiency and increase the hydrogen evolution rate. A dome-type photocathode and a circular disc anode are immersed in an alkaline electrolyte of potassium hydroxide in two cylindrical compartments. This new reactor design concerns utilizing the maximum sunlight during the daytime due to the dome shape and increasing the photocathode active area. Four different types of analyses and simulations, including energy, exergy, electrochemical and fluid flow, are performed to investigate the present hydrogen reactor performance using both Engineering Equation Solver and COMSOL software packages. Thermodynamic and electrochemical equations are solved, including mass, energy, entropy, and exergy balance equations, as well as the electrochemical equations. The proposed flow circulation shows a significant effect to avoid the hydrogen bubble coverage phenomenon. The influences of varying the illumined photocathode surface area, the solar irradiance flux, and the quantum efficiency are studied on the hydrogen evolution rate and the solar to hydrogen efficiency. The present hydrogen generation rate and the overall energy system efficiency are 42.1 μg/s, 4.9%, respectively, occurring at solar irradiance of 600 W/m2 and the illumined area of 840 cm2. The highest hydrogen evolution rate is 60.20 μg/s achieved at the illumined photocathode area of 1200 cm2. The maximum reactor energy efficiency found to be 6.52% occurred at a quantum efficiency of 20%, respectively. The study results further confirm that increasing the illuminated photocathode area increases the solar to hydrogen energy efficiency and the hydrogen production rates. Moreover, the hydrogen production rates increase with an increase in the solar irradiance.