Search Results (11)

Water photoelectrolysis cells based on photoelectrochemical water splitting seem to be an interesting alternative to other traditional green hydrogen generation processes (e.g., water electrolysis). Unfortunately, the practical application of this technology is currently hindered by several difficulties: low solar-to-hydrogen (STH) efficiency, expensive electrode materials, etc. A novel concept, based on a tandem photoelectrolysis cell configuration with an anion-conducting membrane separating the photoanode from the photocathode, has already been proposed in the literature. This approach allows the use of low-cost metal oxide electrodes and nickel-based co-catalysts. In this paper, we conducted a study to evaluate the economic and environmental sustainability of this technology, using the environmental life cycle cost. Preliminary results have revealed two main interesting aspects: the negligible percentage of externalities in the total cost (<0.15%), which means a positive environmental impact, and as evidenced by the net present value (NPV), there are potentially financial conditions that favour future investment. In fact, an NPV higher than 150,000 EUR can be achieved after 15 years. Full article

To meet the application requirements of neutron detectors, a novel large-area microchannel plate photomultiplier tube with a gate function (G-MCP-PMT) was developed in this study. A kind of regular hexagonal mesh electrode as the gated electrode was designed to achieve excellent gating functions for target pulse signals. The photoelectron transmittances for different mesh electrode sizes and voltages were studied via numerical simulations. To increase the effective detection area of the photocathode, an electrostatic-focusing electrode was designed in the G-MCP-PMT. By optimizing the structure of the focusing electrode, an effective photocathode detection surface diameter of 80 mm was achieved based on commercially available MCPs with a diameter of 56 mm. By adjusting the channel diameter configurations of the dual MCPs, the output pulse peak and time response of the large-area G-MCP-PMT can be flexibly adjusted. The experimental results indicate that when the large-area G-MCP-PMT is operated at −2700 V, the gate establishment time is approximately 50 ns. The extinction ratio of the large-area G-MCP-PMT is higher than 3000:1, and the maximum linear output current is greater than 300 mA at 250 ns FWHM, meeting application needs in various fields such as white neutron detection and laser radar. Full article

This investigation reports on the efficacy of a photoelectrocatalysis (PEC) system enhanced by a nitrogen-doped TiO₂ nanocrystal-modified TiO₂ nanotube array (N-TiO₂ NCs/TNTAs) anode paired with a graphene oxide/activated carbon (GO/AC) photocathode for diclofenac removal from effluent. The FE-SEM and EDX analyses validated the elemental composition of the anode—27.56% C, 30.81% N, 6.03% O, and 26.49% Ti. The XRD results confirmed the anatase phase and nitrogen integration, essential for photocatalytic activity enhancement. Quantum chemical simulations provided a comprehensive understanding of the red-shifted absorption bands in N-TiO₂, and UV-vis DRS demonstrated a red-shift in absorption to the visible spectrum, indicating improved light utilization. The PEC configuration achieved a photocurrent density of 9.8 mA/dm², significantly higher than the unmodified and solely nitrogen-doped counterparts at 4.8 mA/dm² and 6.1 mA/dm², respectively. Notably, this system reduced diclofenac concentrations by 58% within 75 min, outperforming standard photocatalytic setups. These findings underscore the potential of N-TiO₂ NCs/TNTAs-AC-GO/PTFE composite material for advanced environmental photoelectrocatalytic applications. Full article

This paper presents an innovative exploration of advanced configurations for enhancing the efficiency of metallic and superconducting photocathodes (MPs and SCPs) produced via pulsed laser deposition (PLD). These photocathodes are critical for driving next-generation free-electron lasers (FELs) and plasma-based accelerators, both of which demand electron sources with improved quantum efficiency (QE) and electrical properties. Our approach compares three distinct photocathode configurations, namely: conventional, hybrid, and non-conventional, focusing on recent innovations. Hybrid MPs integrate a thin, high-performance, photo-emissive film, often yttrium or magnesium, positioned centrally on the copper flange of the photo-injector. For hybrid SCPs, a thin film of lead is used, offering a higher quantum efficiency than niobium bulk. This study also introduces non-conventional configurations, such as yttrium and lead disks partially coated with copper and niobium films, respectively. These designs utilize the unique properties of each material to achieve enhanced photoemission and long-term stability. The novelty of this approach lies in leveraging the advantages of bulk photoemission materials like yttrium and lead, while maintaining the electrical compatibility and durability required for integration into RF cavities. The findings highlight the potential of these configurations to significantly outperform traditional photocathodes, offering higher QE and extended operational lifetimes. This comparative analysis provides new insights into the fabrication of high-efficiency photocathodes, setting the foundation for future advancements in electron source technologies. Full article

The development of photoelectrochemical tandem cells for water splitting with electrodes entirely based on metal oxides is hindered by the scarcity of stable p-type oxides and the poor stability of oxides in strongly alkaline and, particularly, strongly acidic electrolytes. As a novelty in the context of transition metal oxide photoelectrochemistry, a bias-free tandem cell driven by simulated sunlight and based on a CuCrO₂ photocathode and a WO₃ photoanode, both unprotected and free of co-catalysts, is demonstrated to split water while working with strongly acidic electrolytes. Importantly, the Faradaic efficiency for H₂ evolution for the CuCrO₂ electrode is found to be about 90%, among the highest for oxide photoelectrodes in the absence of co-catalysts. The tandem cell shows no apparent degradation in short-to-medium-term experiments. The prospects of using a practical cell based on this configuration are discussed, with an emphasis on the importance of modifying the materials for enhancing light absorption. Full article

Bright electron beams have played a critical role in many recent advances in accelerator technology. Producing bright beams via photo-emission is ultimately limited by the mean transverse energy (MTE), which is determined by the photocathode. This paper discusses the opportunity to generate bright electron beams using an upgraded version of the Argonne Wakefield Accelerator (AWA) photo-injector. The focus of this study is to examine the optimal configurations of the AWA photo-injector to produce 100 pC with a ∼100 nm transverse emittance (corresponding to a 5D brightness ${\mathcal{B}}_5\ge {10}^{15}$ A·m${}^{-2}$). The numerical optimization of the AWA photo-injector operating point, including realistic electromagnetic field maps, is presented for the different types of photocathodes under consideration. Full article

In the present investigation, a one-step hydrothermal approach is proposed to synthesize Li⁺, Rb⁺, and In³⁺intercalated PW₁₂O₄₀ (PTA) thin films. The photoelectrochemical performance of the deposited Li₃PW₁₂O₄₀ (Li−PTA), Rb₃PW₁₂O₄₀ (Rb−PTA), and In₃PW₁₂O₄₀ (In−PTA) photocathodes were investigated using a two-electrode cell configuration of FTO/Li₃PW₁₂O₄₀/(0.1 M I⁻/I³⁻)_aq./Graphite. The energy band gaps of 2.24, 2.11, and 2.13 eV were observed for the Li−PTA, Rb−PTA, and In−PTA films, respectively, as a function of Li⁺, Rb⁺, and In³⁺. The evolution of the spinal cubic crystal structure with increased crystallite size was observed for Rb⁺ intercalation within the PTA Keggin structure, which was confirmed by X-ray diffraction (XRD). Scanning electron microscopy (SEM) revealed a modification in the surface morphology from a rod-like structure to a densely packed, uniform, and interconnected microsphere to small and large-sized microspheres for Li−PTA, Rb−PTA, and In−PTA, respectively. Compositional studies confirmed that the composing elements of Li, Rb, In, P, W, and O ions are well in accordance with their arrangement for Li⁺, Rb⁺, In³⁺, P⁵⁺, W⁶⁺, and O²⁻ valence states. Furthermore, the J-V performance of the deposited photocathode shows power conversion efficiencies (PCE) of 1.25%, 3.03%, and 1.62%, as a function of the incorporation of Li⁺, Rb⁺, and In³⁺ ions. This work offers a one-step hydrothermal approach that is a prominent way to develop Li⁺, Rb⁺, and In³⁺ ions intercalated PTA, i.e., Li₃PW₁₂O_40, Rb₃PW₁₂O₄₀, and In₃PW₁₂O₄₀ photocathodes for competent solar energy harvesting. Full article

Homemade non-critical raw materials such as Ni or NiCu co-catalysts were added at the photocathode of a tandem cell, constituted by photoelectrodes made of earth-abundant materials, to generate green solar hydrogen from photoelectrochemical water splitting. Oxygen evolving at the Ti-and-P-doped hematite/TCO-based photoanode and hydrogen at the cupric oxide/GDL-based photocathode are separated by an anion exchange polymer electrolyte membrane placed between them. The effect of the aforementioned co-catalysts was studied in a complete PEC cell in the presence of the ionomer dispersion and the anionic membrane to evaluate their impact under practical conditions. Notably, different amounts of Ni or NiCu co-catalysts were used to improve the hydrogen evolution reaction (HER) kinetics and the overall solar-to-hydrogen (STH) efficiency of the photoelectrochemical cells. At −0.6 V, in the bias-assisted region, the photocurrent density reaches about 2 mA cm⁻² for a cell with 12 µg cm⁻² of Ni loading, followed by 1.75 mA cm⁻² for the cell configuration based on 8 µg cm⁻² of NiCu. For the best-performing cell, enthalpy efficiency at −0.4 V reaches a first maximum value of 2.03%. In contrast, the throughput efficiency, which is a ratio between the power output and the total power input (solar + electric) provided by an external source, calculated at −1.225 V, reaches a maximum of 10.75%. This value is approximately three times higher than the best results obtained in our previous studies without the use of co-catalysts at the photocathode. Full article

The development of visible-light-responsive semiconductor-based photoelectrodes is a prerequisite for the construction of efficient photoelectrochemical (PEC) cells for solar water splitting. Surface modification with an electrocatalyst on the photoelectrode is effective for maximizing the water splitting efficiency of the PEC cell. Herein, we investigate the effects of surface modification of Ta₃N₅ photoanodes with electrocatalysts consisting of Ni, Fe, and Co oxides, and their mixture, on the PEC oxygen evolution reaction (OER) performance. Among the investigated samples, NiFeO_x-modified Ta₃N₅ (NiFeO_x/Ta₃N₅) photoanodes showed the lowest onset potential for OER. A PEC cell with a parallel configuration consisting of a NiFeO_x/Ta₃N₅ photoanode and an Al-doped La₅Ti₂Cu_0.9Ag_0.1S₅O₇ (LTCA:Al) photocathode exhibited stoichiometric hydrogen and oxygen generation from water splitting, without any external bias voltage. The solar-to-hydrogen energy conversion efficiency (STH) of this cell for water splitting was found to be 0.2% at 1 min after the start of the reaction. In addition, water splitting by a PEC cell with a tandem configuration incorporating a NiFeO_x/Ta₃N₅ transparent photoanode prepared on a quartz insulating substrate as a front-side electrode and a LTCA:Al photocathode as a back side electrode was demonstrated, and the STH was found to be 0.04% at the initial stage of the reaction. Full article

Tandem photo-electro-chemical cells composed of an assembly of a solid electrolyte membrane and two low-cost photoelectrodes have been developed to generate green solar fuel from water-splitting. In this regard, an anion-exchange polymer–electrolyte membrane, able to separate H₂ evolved at the photocathode from O₂ at the photoanode, was investigated in terms of ionic conductivity, corrosion mitigation, and light transmission for a tandem photo-electro-chemical configuration. The designed anionic membranes, based on polysulfone polymer, contained positive fixed functionalities on the side chains of the polymeric network, particularly quaternary ammonium species counterbalanced by hydroxide anions. The membrane was first investigated in alkaline solution, KOH or NaOH at different concentrations, to optimize the ion-exchange process. Exchange in 1M KOH solution provided high conversion of the groups, a high ion-exchange capacity (IEC) value of 1.59 meq/g and a hydroxide conductivity of 25 mS/cm at 60 °C for anionic membrane. Another important characteristic, verified for hydroxide membrane, was its transparency above 600 nm, thus making it a good candidate for tandem cell applications in which the illuminated photoanode absorbs the highest-energy photons (< 600 nm), and photocathode absorbs the lowest-energy photons. Furthermore, hydrogen crossover tests showed a permeation of H₂ through the membrane of less than 0.1%. Finally, low-cost tandem photo-electro-chemical cells, formed by titanium-doped hematite and ionomer at the photoanode and cupric oxide and ionomer at the photocathode, separated by a solid membrane in OH form, were assembled to optimize the influence of ionomer-loading dispersion. Maximum enthalpy (1.7%), throughput (2.9%), and Gibbs energy efficiencies (1.3%) were reached by using n-propanol/ethanol (1:1 wt.) as solvent for ionomer dispersion and with a 25 µL cm⁻² ionomer loading for both the photoanode and the photocathode. Full article

A photoelectrochemical tandem cell (PEC) based on a cathodic hydrophobic gas-diffusion backing layer was developed to produce dry hydrogen from solar driven water splitting. The cell consisted of low cost and non-critical raw materials (CRMs). A relatively high-energy gap (2.1 eV) hematite-based photoanode and a low energy gap (1.2 eV) cupric oxide photocathode were deposited on a fluorine-doped tin oxide glass (FTO) and a hydrophobic carbonaceous substrate, respectively. The cell was illuminated from the anode. The electrolyte separator consisted of a transparent hydrophilic anionic solid polymer membrane allowing higher wavelengths not absorbed by the photoanode to be transmitted to the photocathode. To enhance the oxygen evolution rate, a NiFeO_X surface promoter was deposited on the anodic semiconductor surface. To investigate the role of the cathodic backing layer, waterproofing and electrical conductivity properties were studied. Two different porous carbonaceous gas diffusion layers were tested (Spectracarb^® and Sigracet^®). These were also subjected to additional hydrophobisation procedures. The Sigracet 35BC^® showed appropriate ex-situ properties for various wettability grades and it was selected as a cathodic substrate for the PEC. The enthalpic and throughput efficiency characteristics were determined, and the results compared to a conventional FTO glass-based cathode substrate. A throughput efficiency of 2% was achieved for the cell based on the hydrophobic backing layer, under a voltage bias of about 0.6 V, compared to 1% for the conventional cell. For the best configuration, an endurance test was carried out under operative conditions. The cells were electrochemically characterised by linear polarisation tests and impedance spectroscopy measurements. X-Ray Diffraction (XRD) patterns and Scanning Electron Microscopy (SEM) micrographs were analysed to assess the structure and morphology of the investigated materials. Full article