High-throughput testing of photoelectrochemical cells and materials under well-defined operating conditions can accelerate the discovery of new semiconducting materials, the characterization of the phenomena occurring at the semiconductor-electrolyte interface, or the understanding of the coupled multi-physics transport phenomena of a complete working cell. However, there have been few high-throughput systems capable of dealing with complete cells and applying variations in real-life operating conditions, like temperature or irradiance. Understanding the effects of the variations of these real-life operating conditions on the performance of photoelectrode materials requires reliable and reproducible measurements. In this work, we report on a setup that simultaneously tests ten individual, identical photoelectrochemical cells whilst controlling temperature. The effects of temperature from 26 to 65 °C were studied in tin-doped hematite photoanodes for water splitting - as a reference case - through cyclic voltammetry and electrochemical impedance spectroscopy. The increase of surface-state-mediated charge recombination with temperature mainly penalized the energy conversion efficiency due to the reduction of the photovoltage produced. For parallel measurements in the ten individual cells, standard deviations from 20 to 60 mV for the onset potentials and less than 0.2 mA cm for saturation current densities quantified the reproducibility of the results.

Porous separators are a key component in alkaline water electrolyzers and are significant sources of overpotential. In this paper, porous silicon separators were fabricated by etching precise arrays of cylindrical pores into silicon substrates through lithography. Chemical stability of the silicon-based separators is ensured through the deposition of a silicon nitride layer. Platinum or nickel were vapor-deposited directly on the faces of the separator to complete a zero-gap configuration. Separator porosity () was varied by changing the pore diameter and the pore spacing. These well-controlled porous silicon zero gap electrodes (PSi-ZGEs) were used to study the trade-off between separator resistance and gas-crossover at different porosities. It was found that separator resistances comparable to commercially used Zirfon UTP 500 were achieved at much lower . Gas crossover remained within the explosive limits for ≤ 0.15%. The PSi-ZGEs achieved stable performance at 100 mA cm for 24 hours without significant surface damage in the alkaline electrolyte. In the broad perspective, the current work can pave the path for the development of ionomer-free separators for alkaline water electrolysis which rely on the separator geometry to limit gas-crossover.

The recycling of spent lithium-ion batteries (LIBs) is crucial to sustainably manage resources and protect the environment as the use of portable electronics and electric vehicles (EVs) increases. However, the safe recycling of spent LIBs is challenging, as they often contain residual energy. Left untreated, this can trigger a thermal runaway and result in disasters during the recycling process. For efficient recycling, it is important to withdraw any leftover energy from LIBs, regardless of the processing method that follows the discharge. The electrochemical discharge method is a quick and inexpensive method to eliminate this hazard. This method works by immersing batteries in an aqueous inorganic salt solution to discharge LIBs completely and efficiently. Previously, research focus has been on different inorganic salt solutions that release toxic or flammable gaseous products during discharge. In contrast, we present an entirely new approach for electrochemical discharge - the utilization of an Fe(ii)-Fe(iii) redox couple electrolyte. We show that this medium can be used for efficient LIB deep discharge to a voltage of 2.0 V after rebound, a level that is low enough for safe discharge. To accomplish this, periodic discharge methods were used. In addition, no corrosion on the battery casing was observed. The pH behavior at the poles was also investigated, and it was found that without convection, gas evolution during discharge cannot be avoided. Finally, it was discovered that the battery casing material plays a vital role in electrochemical discharge, and its industrial standardization would facilitate efficient recycling.

This study introduces solid-state tuning of a mesostructured cellular foam (MCF) to enhance hydrogen (H) storage in clathrate hydrates. Grafting of promoter-like molecules (, tetrahydrofuran) at the internal surface of the MCF resulted in a substantial improvement in the kinetics of formation of binary H-THF clathrate hydrate. Identification of the confined hydrate as sII clathrate hydrate and enclathration of H in its small cages was performed using XRD and high-pressure H NMR spectroscopy respectively. Experimental findings show that modified MCF materials exhibit a ∼1.3 times higher H storage capacity as compared to non-modified MCF under the same conditions (7 MPa, 265 K, 100% pore volume saturation with a 5.56 mol% THF solution). The enhancement in H storage is attributed to the hydrophobicity originating from grafting organic molecules onto pristine MCF, thereby influencing water interactions and fostering an environment conducive to H enclathration. Gas uptake curves indicate an optimal tuning point for higher H storage, favoring a lower density of carbon per nm. Furthermore, a direct correlation emerges between higher driving forces and increased H storage capacity, culminating at 0.52 wt% (46.77 mmoles of H per mole of HO and 39.78% water-to-hydrate conversions) at 262 K for the modified MCF material with fewer carbons per nm. Notably, the substantial H storage capacity achieved without energy-intensive processes underscores solid-state tuning's potential for H storage in the synthesized hydrates. This study evaluated two distinct kinetic models to describe hydrate growth in MCF. The multistage kinetic model showed better predictive capabilities for experimental data and maintained a low average absolute deviation. This research provides valuable insights into augmenting H storage capabilities and holds promising implications for future advancements.

This study investigates the hydrogen evolution reaction (HER) efficiency of two photosystems incorporating an all-inorganic molecular thiomolybdate [MoS] cluster as a HER catalyst. First, we delve into the performance of a homogeneous [MoS]/[Ru(bpy)] (Mo/Ru) dyad which demonstrates high turnover frequencies (TOFs) and apparent quantum yields (AQYs) at 445 nm approaching the level of 0.5%, yet its performance is marked by pronounced deactivation. In contrast, a heterogeneous approach involves anchoring [MoS] onto graphitic carbon nitride (GCN) nanosheets through weak electrostatic association with its triazine/heptazine scaffold. [MoS]/GCN (Mo/GCN) displays effective H generation under visible light, with TOF metrics on par with those of its homogeneous analog. Although substantial leaching of [MoS] species from the Mo/GCN surface occurs, the remaining {Mo}-based centers demonstrate impressive stability, leading to enduring HER performance, starkly distinguishing it from the homogeneous Mo/Ru photosystem. Photoluminescence (PL) quenching experiments confirm that the performance of Mo/GCN is not limited by the quality of the inorganic interface, but could be optimized by using higher surface area supports or a higher concentration of [MoS] sites. Our findings showcase complexities underlying the evaluation and comparison of photosystems comprising well-defined catalytic centers and pave the way for developing analogous surface-supported (photo)catalysts with broad use in energy applications.

Perovskite solar cells have shown considerable developments in the last decade, and commercial applications are drawing closer. In this article, we present a techno-economic study of perovskite PV technologies. We compare published data on manufacturing costs of single-junction perovskite modules and find that they are dependent on the module design (rigid or flexible) and vary from 10 to almost 100 € per m. We calculate the LCOE as a function of module efficiency and stability for a set of four module cost scenarios at 12.5, 25, 50, and 100 € per m. The resulting LCOE varies from 4.3 to 25.5 ct kW h and shows low potential for immediate competition with crystalline silicon PV in the utility sector. Perovskite PV's competitive advantage lies in both lighter and less rigid modules, and in the development of tandem modules together with silicon. We hence extend the LCOE equation to highlight the benefit of producing flexible low-weight modules by roll-to-roll manufacturing, and modify the LCOE maps to showcase the benefits of tandem modules. Based on learning curve analyses applied to the CAPEX of single-junction and tandem modules, we develop three scenarios for the evolution of the LCOE of perovskite modules from 2025 to 2050. Under the optimistic scenarios, we find that the LCOE could reduce to 2.8 ct kW h by 2050.

Integration of molecular catalysts inside polymeric scaffolds has gained substantial attention over the past decade, as it provides a path towards generating systems with enhanced stability as well as enzyme-like morphologies and properties. In the context of solar fuels research and chemical energy conversion, this approach has been found to improve both rates and energy efficiencies of a range of catalytic reactions. However, system performance still needs to be improved to reach technologically relevant currents and stability, parameters that are heavily influenced by the nature of the incorporated molecular catalyst. Here, we have focused on the integration of a biomimetic {Fe(μ-adt)(CO)} (-CHNHCHS-, azadithiolate or adt) based active site ("[2Fe2S]"), inspired by the catalytic cofactor of [FeFe] hydrogenases, within a synthetic polymeric scaffold using free radical polymerization. The resulting metallopolymers [2Fe2S][DMAEMA][PyBMA] (DMAEMA = dimethylaminoethyl methacrylate as water soluble monomer; PyBMA = 4-(pyren-1-yl)-butyl methacrylate as hydrophobic anchor for heterogenization) were found to be active for electrochemical H production in neutral aqueous media. The pyrene content was varied to optimize durability and activity. Following immobilization on multiwalled carbon nanotubes (MWNT) the most active metallopolymer, containing ∼2.3 mol% of PyBMA, could reach a turnover number for hydrogen production (TON) of ∼0.4 ×10 over 20 hours of electrolysis at an overpotential of 0.49 V, two orders of magnitude higher than the isolated catalyst counterpart. The study provides a synthetic methodology for incorporating catalytic units featuring second coordination sphere functional groups, and highlights the benefit of the confinement within the polymer matrix for catalytic performance.

Cobalt(ii) complexes featuring hexadentate amino-pyridyl ligands have been recently discovered as highly active catalysts for the Hydrogen Evolution Reaction (HER), whose high performance arises from the possibility of assisting proton transfer processes intramolecular routes involving detached pyridine units. With the aim of gaining insights into such catalytic routes, three new proton reduction catalysts based on amino-polypyridyl ligands are reported, focusing on substitution of the pyridine position. Specifically, a carboxylate (C2) and two hydroxyl substituted pyridyl moieties (C3, C4) are introduced with the aim of promoting intramolecular proton transfer which possibly enhances the efficiency of the catalysts. Foot-of-the-wave and catalytic Tafel plot analyses have been utilized to benchmark the catalytic performances under electrochemical conditions in acetonitrile using trifluoroacetic acid as the proton source. In this respect, the cobalt complex C3 turns out to be the fastest catalyst in the series, with a maximum turnover frequency (TOF) of 1.6 (±0.5) × 10 s, but at the expense of large overpotentials. Mechanistic investigations by means of Density Functional Theory (DFT) suggest a typical ECEC mechanism ( a sequence of reduction - E - and protonation - C - events) for all the catalysts, as previously envisioned for the parent unsubstituted complex C1. Interestingly, in the case of complex C2, the catalytic route is triggered by initial protonation of the carboxylate group resulting in a less common (C)ECEC mechanism. The pivotal role of the hexadentate chelating ligand in providing internal proton relays to assist hydrogen elimination is further confirmed within this novel class of molecular catalysts, thus highlighting the relevance of a flexible polypyridine ligand in the design of efficient cobalt complexes for the HER. Photochemical studies in aqueous solution using [Ru(bpy)] (where bpy = 2,2'-bipyridine) as the sensitizer and ascorbate as the sacrificial electron donor support the superior performance of C3.

In recent years, liquid fuels from renewable carbon that can replace fossil ones with minimal infrastructure changes have attracted increasing interest in decarbonising the heavy-duty long-haul sector. Here we focus on dimethyl ether (DME), a promising alternative to diesel due to its high cetane number, oxygen content, and more efficient and cleaner propulsion that results in low particulate matter and sulphur oxide emissions. Going well beyond previous studies that quantified the environmental impact of DME, often in terms of global warming, here we evaluate DME use in heavy-duty trucks in the context of seven planetary boundaries, all essential for maintaining the Earth's stability. Focusing on several scenarios differing in the feedstock origin, we find that routes based on fossil carbon, either in the form of coal, natural gas, or captured CO from fossil plants, would increase the greenhouse gas emissions relative to the business-as-usual. Only scenarios based on renewable carbon could reduce the impacts on climate change, while hydrogen from biomass gasification coupled with carbon capture and storage (CCS) and DME from biomass gasification with CCS could enable an environmentally sustainable operation within all the planetary boundaries. Overall, our work opens up new avenues for the environmental assessment of fuels considering the finite capacity of the Earth system to guide research and policy-making more sensibly.

We report a push-pull BODIPY-based dye functionalised with an electronegative SF group at the position for applications in photocathodes in tandem dye-sensitized solar cells (DSSCs). The push-pull character enhances charge-transfer from the mesoporous NiO cathode surface towards the redox mediator. A Knoevenagel condensation reaction was used to introduce the carboxylic acid to anchor the dye to the oxide surface, a styryl linker which increases the conjugation in the molecule and shifts the absorption to the red. The room-temperature synthesis and high yields, make the dye promising for manufacture on a large scale. The dye was applied in p-DSSCs giving a power conversion efficiency (0.066%), a short circuit photocurrent ( ) of 3.84 mA cm, open circuit voltage ( ) of 58 mV and fill factor of 30%.

Determining the optimum layer thickness, for the anode and cathode, is of utmost importance for minimizing the costs of the alkaline direct ethanol fuel cell (DEFC) without lowering the electrochemical performance. In this study, the influence of layer thickness on the performance of the ethanol oxidation reaction (EOR) and oxygen reduction reaction (ORR) in an alkaline medium and resistance was investigated. The prepared gas diffusion electrodes (GDEs) were fully characterized, with scanning electron microscopy to determine the layer thickness and electrochemically in half-cell configuration. Cyclic voltammetry and polarization curve measurements were used to determine the oxidation and reduction processes of the metals, the electrochemical active surface area, and the activity towards the ORR and EOR. It was demonstrated that realistic reaction conditions can be achieved with simple and fast half-cell GDE measurements. Single cell measurements were conducted to evaluate the influence of factors, such as membrane or ethanol crossover. In addition, electrochemical impedance spectra investigation was performed to identify the effect of layer thickness on resistance. This successfully demonstrated that the optimal layer thicknesses and high maximum power density values (120 mW cm) were achieved with the Pt-free catalysts and membranes used.

Electrochemical reduction of carbon dioxide (COR) poses substantial promise to convert abundant feedstocks (water and CO) to value-added chemicals and fuels using solely renewable energy. However, recent membrane-electrode assembly (MEA) devices that have been demonstrated to achieve high rates of COR are limited by water management within the cell, due to both consumption of water by the COR reaction and electro-osmotic fluxes that transport water from the cathode to the anode. Additionally, crossover of potassium (K) ions poses concern at high current densities where saturation and precipitation of the salt ions can degrade cell performance. Herein, a device architecture incorporating an anion-exchange membrane (AEM) with internal water channels to mitigate MEA dehydration is proposed and demonstrated. A macroscale, two-dimensional continuum model is used to assess water fluxes and local water content within the modified MEA, as well as to determine the optimal channel geometry and composition. The modified AEMs are then fabricated and tested experimentally, demonstrating that the internal channels can both reduce K cation crossover as well as improve AEM conductivity and therefore overall cell performance. This work demonstrates the promise of these materials, and water-management strategies in general, in handling some of the major hurdles in the development of MEA devices for COR.

Hybrid organic-inorganic perovskite solar cells (PSCs) are attractive printable, flexible, and cost-effective optoelectronic devices constituting an alternative technology to conventional Si-based ones. The incorporation of low-dimensional materials, such as two-dimensional (2D) materials, into the PSC structure is a promising route for interfacial and bulk perovskite engineering, paving the way for improved power conversion efficiency (PCE) and long-term stability. In this work, we investigate the incorporation of 2D bismuth telluride iodide (BiTeI) flakes as additives in the perovskite active layer, demonstrating their role in tuning the interfacial energy-level alignment for optimum device performance. By varying the concentration of BiTeI flakes in the perovskite precursor solution between 0.008 mg mL and 0.1 mg mL, a downward shift in the energy levels of the perovskite results in an optimal alignment of the energy levels of the materials across the cell structure, as supported by device simulations. Thus, the cell fill factor (FF) increases with additive concentration, reaching values greater than 82%, although the suppression of open circuit voltage ( ) is reported beyond an additive concentration threshold of 0.03 mg mL. The most performant devices delivered a PCE of 18.3%, with an average PCE showing a +8% increase compared to the reference devices. This work demonstrates the potential of 2D-material-based additives for the engineering of PSCs energy level optimization at perovskite/charge transporting layer interfaces.

The decarbonisation of the transportation sector is key to meeting the climate goals. Whilst the electrification of road passenger transportation is proving to be a viable low-carbon solution in many contexts, a viable pathway towards a decarbonised aviation sector remains opaque. In this context, so-called e-fuels produced the combination of HO, CO and renewable energy may have promise owing to their compatibility with existing infrastructure. Most studies on e-fuels focus only on the economic dimension, neglecting their environmental performance and associated costs. Here, we present a techno-economic evaluation and cradle-to-grave life cycle assessment of Fischer-Tropsch (FT) e-jet fuels produced at different locations in Europe from a range of CO and green H sources to comprehensively assess their potential in aviation, explicitly accounting for externalities. Our results show that e-jet fuel is at present much more expensive (at least 5.4-fold) than its fossil analogue, even when externalities are included (, at least 2.3 fold the current cost of fossil jet fuel). Furthermore, e-jet fuels could exacerbate the damage to human health and ecosystems despite showing lower carbon footprint and resource scarcity impacts than their fossil counterparts. Overall, e-jet fuel could become more economically and environmentally attractive by reducing the cost and impact of CO and green H and, more specifically, the electricity used in their production processes. In this regard, the production plant's location emerges as a critical factor due to the costs associated with balancing the intermittency of site-specific renewables.

Green hydrogen could contribute to climate change mitigation, but its greenhouse gas footprint varies with electricity source and allocation choices. Using life-cycle assessment we conclude that if electricity comes from additional renewable capacity, green hydrogen outperforms fossil-based hydrogen. In the short run, alternative uses of renewable electricity likely achieve greater emission reductions.

In this work, we report the design and the preparation of two new dyes and a molecular dyad for the photoelectrochemical hydrogen production from water in a dye-sensitized photoelectrochemical cell (DSPEC). We designed dyes that include a benzothiadiazole (BTD) and an indacenodithiophene (IDT) units, and we obtained a new molecular dyad by covalent coupling with the cobalt diimine-dioxime catalyst. The introduction of the benzothiadiazole core in the structure improves the absorption properties and leads to an extension of the spectrum in the visible range up to 650 nm. The photoelectrochemical properties of the new dyad were evaluated on pristine and lithium-doped NiO electrodes. We demonstrate that increasing the light harvesting efficiency of the dyad by introducing a IDT-BTD chromophore is clearly beneficial for the photoelectrochemical activity. We also demonstrate that lithium doping of NiO, which improves the electronic conductivity of the mesoporous film, leads to a significant increase in performance, in terms of TON and F.E., more than doubled with our new dyad. This BTD-based molecular system outperforms the results of previously reported dyads using the same catalyst.

Rapid advances in electrocatalytic ammonia synthesis are impeded by laborious detection methods commonly used in the field and by constant risk of external contaminations, which generates misleading false positives. We developed a facile real-time GC-MS method for sensitive isotope NH quantification, requiring no external sample manipulations. This method ensures high detection reliability paramount to accelerate (electro-)catalyst screening.

Biologists and engineers are making tremendous efforts in contributing to a sustainable and green society. To that end, there is growing interest in waste management and valorisation. Lignocellulosic biomass (LCB) is the most abundant material on the earth and an inevitable waste predominantly originating from agricultural residues, forest biomass and municipal solid waste streams. LCB serves as the renewable feedstock for clean and sustainable processes and products with low carbon emission. Cellulose and hemicellulose constitute the polymeric structure of LCB, which on depolymerisation liberates oligomeric or monomeric glucose and xylose, respectively. The preferential utilization of glucose and/or absence of the xylose metabolic pathway in microbial systems cause xylose valorization to be alienated and abandoned, a major bottleneck in the commercial viability of LCB-based biorefineries. Xylose is the second most abundant sugar in LCB, but a non-conventional industrial substrate unlike glucose. The current review seeks to summarize the recent developments in the biological conversion of xylose into a myriad of sustainable products and associated challenges. The review discusses the microbiology, genetics, and biochemistry of xylose metabolism with hurdles requiring debottlenecking for efficient xylose assimilation. It further describes the product formation by microbial cell factories which can assimilate xylose naturally and rewiring of metabolic networks to ameliorate xylose-based bioproduction in native as well as non-native strains. The review also includes a case study that provides an argument on a suitable pathway for optimal cell growth and succinic acid (SA) production from xylose through elementary flux mode analysis. Finally, a product portfolio from xylose bioconversion has been evaluated along with significant developments made through enzyme, metabolic and process engineering approaches, to maximize the product titers and yield, eventually empowering LCB-based biorefineries. Towards the end, the review is wrapped up with current challenges, concluding remarks, and prospects with an argument for intense future research into xylose-based biorefineries.

The cobalt tetraazamacrocyclic [Co(NH)Cl] complex is becoming a popular and versatile catalyst for the electrocatalytic evolution of hydrogen, because of its stability and superior activity in aqueous conditions. We present here a benchmarking of its performances based on the thorough analysis of cyclic voltammograms recorded under various catalytic regimes in non-aqueous conditions allowing control of the proton concentration. This allowed a detailed mechanism to be proposed with quantitative determination of the rate-constants for the various protonation steps, as well as identification of the amine function of the tetraazamacrocyclic ligand to act as a proton relay during H evolution.

This study examines two strategies-homo- and heterogeneous approaches for the light-driven oxidation of benzyl alcohol in dye-sensitised photoelectrochemical cells (DSPECs). The DSPEC consists of a mesoporous anatase TiO film on FTO (fluorine-doped tin oxide), sensitised with the thienopyrroledione-based dye as the photoanode and an FTO-Pt cathode combined with a redox-mediating catalyst. The homogeneous catalyst approach entails the addition of the soluble 2,2,6,6-tetramethylpiperidine-1-oxyl () to the DSPEC anolyte, while the heterogeneous strategy employs immobilisation of a analogue with a silatrane anchor () onto the photoanode. Irradiation of the photoanode oxidises the -moiety to , both in the homogeneous and the heterogeneous system, which is a chemical oxidant for benzyl alcohol oxidation. Photoanodes containing the heterogeneous demonstrate decreased photocurrent, attributed to introducing alternative pathways for electron recombination. Moreover, the immobilised demonstrates an insufficient ability to mediate electron transfer from the organic substrate to the photooxidised dye, resulting in device instability. In contrast, the homogeneous approach with as a redox-mediating catalyst in the anolyte is efficient in the light-driven oxidation of benzyl alcohol to benzaldehyde over 32 hours, promoted by the efficient electron mediation of between and the organic substrate. Our work demonstrates that operational limitations in DSPECs can be solved by rational device design using diffusion-mediated electron transfer steps.

The production of value added C1 and C2 compounds within CO electrolyzers has reached sufficient catalytic performance that system and process performance - such as CO utilization - have come more into consideration. Efforts to assess the limitations of CO conversion and crossover within electrochemical systems have been performed, providing valuable information to position CO electrolyzers within a larger process. Currently missing, however, is a clear elucidation of the inevitable trade-offs that exist between CO utilization and electrolyzer performance, specifically how the faradaic efficiency of a system varies with CO availability. Such information is needed to properly assess the viability of the technology. In this work, we provide a combined experimental and 3D modelling assessment of the trade-offs between CO utilization and selectivity at 200 mA cm within a membrane-electrode assembly CO electrolyzer. Using varying inlet flow rates we demonstrate that the variation in spatial concentration of CO leads to spatial variations in faradaic efficiency that cannot be captured using common 'black box' measurement procedures. Specifically, losses of faradaic efficiency are observed to occur even at incomplete CO consumption (80%). Modelling of the gas channel and diffusion layers indicated that at least a portion of the H generated is considered as avoidable by proper flow field design and modification. The combined work allows for a spatially resolved interpretation of product selectivity occurring inside the reactor, providing the foundation for design rules in balancing CO utilization and device performance in both lab and scaled applications.