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The potential of methanol reforming systems to greatly improve productivity in chemical reactors has been limited, due in part, to the effect of mass transfer limitations on the production of hydrogen. There is a need to determine whether or not a microchannel reforming reactor system is operated in a mass transfer-controlled regime, and provide the necessary criteria so that mass transfer limitations can be effectively eliminated in the reactor. Three-dimensional numerical simulations were carried out using computational fluid dynamics to investigate the essential characteristics of mass transport processes in a microchannel reforming reactor and to develop criteria for determining mass transfer limitations. The reactor was designed for thermochemically producing hydrogen from methanol by steam reforming. The mass transfer effects involved in the reforming process were evaluated, and the role of various design parameters was determined for the thermally integrated reactor. In order to simplify the mathematics of mass transport phenomena, use was made of dimensionless numbers or ratios of parameters that numerically describe the physical properties in the reactor without units. The results indicated that the performance of the reactor can be greatly improved by means of proper design of catalyst layer thickness and through adjusting feed composition to minimize or reduce mass transfer limitations in the reactor. There is not an effective method to reduce channel dimensions if the flow rate remains constant, or to reduce fluid velocities if the residence time is kept constant. The rate of the reforming reaction is limited by mass transfer near the entrance of the reactor and by kinetics further downstream, when the heat transfer in the autothermal system is efficient. Finally, the criteria that can be used to distinguish between different mass transport and kinetics regimes in the reactor with a first-order reforming reaction were presented.

Energy from renewable resources has been growing in popularity, which ultimately helps reduce emissions of greenhouse gases (GHGs) and contaminants. Since hydrogen (H2) has a higher combustion production of energy than hydrocarbon fuels, it has been identified as a clean, sustainable, and environmentally friendly energy source. There are several benefits to producing biohydrogen (bioH2) from renewable sources, including lower cost and increased sustainability. Among the bioH2 production processes, dark fermentation supports commercialization and scale-up for industrial applications. This paper considers the various bioreactors, such as anaerobic sequencing batch, continuous stirred, up-flow, fixed-bed, and membrane reactors, and their operational approaches for bioH2 production. This review paper also performs the bibliometric analysis method to identify historical and current developments in a particular field of reactor configuration studies. Furthermore, the main variables influencing reactor performance and methods for increasing process efficiency considering economic and environmental aspects are addressed. The results revealed that continuously stirred reactors are widely utilized for bioH2 production as a cost-effective reactor configuration. Moreover, the membrane bioreactors and fixed-bed reactors are yielded higher bioH2 performance than other configurations. Nevertheless, high energy consumption and costs have presented the need for further development of reactors. Consequently, future recommendations to solve the critical problems faced in reactor configurations, the gaps in the literature, and the points that need improvement were comprehensively reported. [ABSTRACT FROM AUTHOR]

Featured Application: This research work provides information about the conceptual design of a batch reactor to produce biodiesel and biolubricants from waste cooking oil at a commercial scale using a two-step transesterification process catalyzed by sodium methoxide. Biodiesel and biolubricants play strategic roles in green technologies, as they can be produced in biorefineries. The design of industrial facilities is essential to assess the industrial implementation of these processes, with few studies about this subject in the literature. The aim of this work was to produce biodiesel and a biolubricant from waste cooking oil through double transesterification with methanol and trimethylolpropane, obtaining high conversion values (>97 and 98%, respectively). The biolubricant (characterized according to the UNE-14214 standard) had a density of 951 kg·m−3, a viscosity of 127 cSt (at 40 °C), an acidity value of 0.43 mgKOH·g−1, flash and combustion points of 225 and 232 °C, and an oxidation stability of 6 h through the Rancimat method. Also, a kinetic study was carried out (at temperatures ranging from 80 to 140 °C and with catalyst concentrations from 0.3 to 0.9% w/w and working pressures from 210 to 760 mmHg) to establish the main kinetic parameters, obtaining a second-order reaction and an activation energy of 17.8 kJ·mol−1. Finally, a conceptual design was included, considering the main components of the facility. Thus, the projected plant worked in a discontinuous regime (producing 2 cubic meters per day), pointing out the feasibility of this plant at an industrial scale. [ABSTRACT FROM AUTHOR]

This study aimed to enhance galactooligosaccharide (GOS) yield by maintaining high lactose concentration levels using osmotic membrane distillation (OMD) throughout the synthesis. The main problem influencing GOS yield during transgalactosylation is the decrease of lactose concentration over extended reaction periods. By integrating OMD with a continuous stirred batch reactor, water was progressively removed from the reaction medium. Compared to a standard batch reactor, the OMD-integrated system not only increased GOS yield by a maximum of 20.1% but also reduced the time needed for equivalent lactose conversion about 15–90 min. This integration particularly boosted the formation of longer-chain GOS. A consistent GOS yield of 67% was achieved, with up to 28% lactose conversion, surpassing the non-integrated reactor's performance. The proposed reactor design shows promise for enhancing GOS production efficiency while concurrently concentrating the reaction medium in a single step. [ABSTRACT FROM AUTHOR]

This study investigates the self-sustaining traveling wave of nuclear fission in a uranium dicarbide medium by numerically solving a system of partial differential equations. The primary focus is on the neutron diffusion equation and nuclide balance equations, which are crucial for understanding the behavior of fission waves. By solving these equations, we aim to determine the propagation characteristics and assess the stability of nuclear fission waves in uranium dicarbide. Numerical analysis provides significant insights into the dynamics of neutron distribution and nuclide evolution, enhancing our understanding of the underlying physical processes and their implications for traveling wave reactor design.

Abstract This work presents a novel method and reactor design for measuring photocatalytic activity. This method allows continuous in situ monitoring of the decrease in pollutant concentration in a liquid dispersion containing the tested photocatalyst. Due to the presence of the photocatalyst in the liquid dispersion, the standard Beer-Lambert absorption law cannot be used directly to determine pollutant concentration in photocatalytic measurements. Therefore, the presented in situ measurement method also utilizes a newly derived modification of the absorption law, which, in addition to absorption, also considers the scattering effect caused by the dispersed photocatalyst. Repeated correlation analysis showed an average deviation of only 1.04% from approximately 500 measurements. At the same time, the measured points obtained by the presented method were within the uncertainty intervals of the standard method for measuring photocatalytic activity. It has been demonstrated that this novel continuous in situ measurement method can replace the current standard measurement method and can provide an even more consistent and faster way of testing photocatalytic materials. In addition, a novel and open source (patented experimental setup for the photocatalytic reactor system, consisting of a spectrometric laser and probe, is fully described in this paper.

AbstractSmall pressurized water reactors can feature boron-free operation, natural circulation mode, reduced-height assemblies, and/or long refueling cycles. This paper attempts to explore core design optimization for each of these design evolutions. In consequence, five core design layouts are developed incorporating boron-free operation with continuous control rod insertion, natural circulation with low burnup/low power density design, natural circulation with high burnup/low power density design, forced circulation with standard core power density design, and forced circulation with high power density design. These cores’ performance is compared to a standard four-loop pressurized water reactor. The design process aims to improve the fuel cycle cost under safety constraints through core design optimization using the CASMO4E/SIMULATE3 reactor physics codes and the FRAPCON4.1 fuel performance assessment tool. Core modeling assumes standard 17×17 PWR fuel assemblies loaded with low enriched uranium up to 5 wt% or low enriched uranium plus (i.e. below 10 wt% enrichment) pellets with gadolinium oxide as the burnable poison. Satisfactory core and fuel performances are obtained for all the designed cores under steady state and considered overpower transients. For low power density operation, long cycle lengths are achieved reaching 2.5-year and 5-year cycles, and peak rod-average burnup is pushed to 83 MWd/kgU. Other cycle lengths are maintained at 18 months. Boron-free operation exhibits the ability to achieve longer cycle lengths at the cost of higher peaking factors leading to high local power and fuel temperatures, which prevents sizable power uprates and is deemed uneconomical. Fuel assembly height reduction allows coolant velocity retrofit, which enables higher core power density without violating the structural integrity of the fuel assembly. As a result, a core power density of 123 kW/L is reached where total cladding hoop strain becomes the limiting parameter. [ABSTRACT FROM AUTHOR]

In the present study, a lab-scale for closed thermochemical heat storage reactor design is performed for seasonal thermochemical energy storage using magnesium chloride hexahydrate based on dehydration and hydration processes. Firstly, the closed reactor and plate heat exchanger are studied. Then, reactor layout modifications are examined. The dehydration process is performed under 95°C. During hydration, plates' temperature ranges from 20°C to 30°C. The impact of adding zeolite13X-4A to magnesium chloride hexahydrate is examined. The addition of zeolite13X-4A to magnesium chloride hexahydrate of 1/4 mass ratio improves the hydration process and increases its efficiency. [ABSTRACT FROM AUTHOR]

The Fischer–Tropsch Synthesis process is projected to have a significant impact in the near future due to its potential for synthesizing sustainable fuels from biomass, carbon dioxide and organic wastes. In this catalytic process, catalyst activation plays a major role in the overall performance of Fischer–Tropsch Synthesis. Catalyst activation temperatures are considerably higher than the typical operating conditions of industrial reactors. Consequently, ex situ activation is often required for industrial Fischer–Tropsch Synthesis processes. This study evaluated the influence of different activation approaches (in situ, ex situ, passivation and low-temperature activation). Catalytic experiments were conducted in a fixed-bed reactor at 230 °C and 20 bar·g using a reference supported Co/γ-Al2O3 catalyst. Experimental results demonstrate that catalysts can be effectively reduced ex situ. This work reveals that re-activation of the catalyst after ex situ reduction is unnecessary, as the reaction conditions themselves re-reduce any superficial oxides formed, owing to the reducing nature of the reactant mixture. This approach could simplify reactor design by enabling temperature requirements to match operating conditions (e.g., 230 °C), thereby reducing both investment and operational costs and eliminating additional catalyst preparation steps. [ABSTRACT FROM AUTHOR]

Seed aging adversely affects agricultural productivity by reducing germination rates and seedling vigor, leading to significant costs for seed banks and companies due to the need for frequent seed renewals. This study demonstrated the use of plasma-activated water (PAW), generated by a solarpowered corona dielectric barrier discharger, to enhance germination rates of spinach seeds that had been stored at 4 °C for 23 years. Treating seeds with PAW at 17 kV for 15 min improved germination (by 135%) and seedling growth compared to untreated seeds. Through detailed analysis, beneficial PAW properties for seed development were identified, and a molecular mechanism for this rejuvenation is proposed. The solar-powered microreactor used in this study is considered to represent a significant advancement in seed treatment technology, offering a sustainable solution to meet growing food demands while addressing environmental and resource sustainability challenges. [ABSTRACT FROM AUTHOR]

Liquefied petroleum gas (LPG) is known as clean fuel and its importance will be continued in the future. However, most of LPG is currently produced from fossil resources. Thus, producing LPG from CO2 as a renewable source is significant for achieving carbon neutrality. One possible way to produce LPG from CO2 is through an indirect pathway via methanol/dimethyl ether and propylene/butene. The final step of this pathway is the hydrogenation reaction of olefins to produce paraffins. Although H2O may coexist in this reaction, there have been few studies to investigate reaction kinetics of propylene hydrogenation in the presence of H2O. Here, we measured the propylene conversion over different four catalysts: Pt/α-Al2O3, Pd/α-Al2O3, Pt/ZrO2, and Pd/ZrO2. We varied a reaction temperature and concentrations of propylene, H2 and H2O in the feed. We found that above 200 °C the propylene conversion was negatively affected by the reaction temperature and the propylene concentration, while it was positively affected by the H2 concentration. We also found that the dependence of propylene conversion on H2O concentration depended on the catalysts. To reproduce the measured results, a kinetic model based on the Langmuir-Hinshelwood mechanism was developed over Pt/ZrO2 which showed the best reaction performance among the catalysts used. A two-dimensional reactor model consisting of mass and heat balance equations was developed for exploring the desirable reactor type. The simulations showed that the externally cooled reactor with a catalyst density gradient was the most suitable for propylene hydrogenation in terms of heat management and propylene conversion. [ABSTRACT FROM AUTHOR]

Sustainable production of carbon-based products is urgently needed. A novel directed flow-through microbial electrosynthesis (MES) reactor was designed and characterized for carbon dioxide (CO 2) conversion to C2–C6 carboxylates. Three-times denser biofilm, volumetric current density, and productivity were achieved compared with the state of the art. Biomass-specific production rates were maintained over more than 200 days, yet still an order of magnitude lower than that achieved by acetogens in syngas fermentation. Volumetric productivity in MES was comparable with that from syngas fermentation. Clostridium luticellarii and Eubacterium limosum were the dominant species. Carbon-based products are essential to society, yet producing them from fossil fuels is unsustainable. Microorganisms have the ability to take up electrons from solid electrodes and convert carbon dioxide (CO 2) to valuable carbon-based chemicals. However, higher productivities and energy efficiencies are needed to reach a viability that can make the technology transformative. Here, we show how a biofilm-based microbial porous cathode in a directed flow-through electrochemical system can continuously reduce CO 2 to even-chain C2–C6 carboxylic acids over 248 days. We demonstrate a threefold higher biofilm concentration, volumetric current density, and productivity compared with the state of the art. Most notably, the volumetric productivity (VP) resembles those achieved in laboratory-scale and industrial syngas (CO-H 2 -CO 2) fermentation and chain elongation fermentation. This work highlights key design parameters for efficient electricity-driven microbial CO 2 reduction. There is need and room to improve the rates of electrode colonization and microbe-specific kinetics to scale up the technology. Graphical abstract [Display omitted] Microbial electrosynthesis (MES) of carboxylic acids from CO 2 and electricity has been validated for over a decade, now reaching Technology Readiness Levels 3/4 in laboratory settings. However, process optimization is needed before demonstrating an industrial prototype. Key challenges for full-scale implementation include ensuring production stability. Critical areas to investigate and demonstrate are: (i) the impact of CO 2 feed stream composition and properties; (ii) the short- and long-term effects of renewable electricity supply intermittency; and (iii) the flexibility of MES operations and the integrated process, including up- and downstream processes. Moreover, a comprehensive market analysis is required for each target product. For instance, hexanoic acid, which serves as a precursor for nylon, plasticizers, lubricants, pharmaceuticals, fragrances, fuels, and animal feed, necessitates the development of business models that consider complete supply chains and systems. Carbon-based products are crucial to society. However, their production from fossil-based carbon is unsustainable. We developed a scalable microbial electrosynthesis process that produces medium-chain carboxylic acids from CO 2 and renewable electricity, using microorganisms as a catalyst. This represents a promising avenue for generating low CO 2 -footprint precursors for the chemical, fuel, feed, and food industries. [ABSTRACT FROM AUTHOR]

Experimentally screening catalysts for performance, selectivity, or lifetime is one of the key steps in the development and research of novel catalytic materials. Commonly, however, complications from heat or mass transport limitations, mixing, thermodynamics, or experimental designs can cloud the interpretation and differentiation of the kinetic rate behavior of catalysts. Herein, guidelines for proper equipment setups and experimental designs are presented with the hope of improving kinetic resolution of catalyst screening results for increased data fidelity. [ABSTRACT FROM AUTHOR]

This study investigates the self-sustaining traveling wave of nuclear fission in a uranium dicarbide medium by numerically solving a system of partial differential equations. The primary focus is on the neutron diffusion equation and nuclide balance equations, which are crucial for understanding the behavior of fission waves. By solving these equations, we aim to determine the propagation characteristics and assess the stability of nuclear fission waves in uranium dicarbide. Numerical analysis provides significant insights into the dynamics of neutron distribution and nuclide evolution, enhancing our understanding of the underlying physical processes and their implications for traveling wave reactor design. [ABSTRACT FROM AUTHOR]

Direct oxidation of fuels such as methanol in proton-exchange membrane fuel cells at practical current densities with acceptable catalyst loadings is not as economically attractive as conversion of methanol fuel to a hydrogen-rich mixture of gases via steam reforming and subsequent electrochemical conversion of the hydrogen-rich fuel stream to direct current in the fuel cell. The potential of methanol reforming systems to greatly improve productivity in chemical reactors has been limited, due in part, to the effect of mass transfer limitations on the production of hydrogen. There is a need to determine whether or not a microchannel reforming reactor system is operated in a mass transfer-controlled regime, and provide the necessary criteria so that mass transfer limitations can be effectively eliminated in the reactor. Three-dimensional numerical simulations were carried out using computational fluid dynamics to investigate the essential characteristics of mass transport processes in a microchannel reforming reactor and to develop criteria for determining mass transfer limitations. The reactor was designed for thermochemically producing hydrogen from methanol by steam reforming. The mass transfer effects involved in the reforming process were evaluated, and the role of various design parameters was determined for the thermally integrated reactor. In order to simplify the mathematics of mass transport phenomena, use was made of dimensionless numbers or ratios of parameters that numerically describe the physical properties in the reactor without units. The results indicated that the rate of the reforming reaction is limited by mass transfer near the entrance of the reactor and by kinetics further downstream, when the heat transfer in the autothermal system is efficient. There is not an effective method to reduce channel dimensions if the flow rate remains constant, or to reduce fluid velocities if the residence time is kept constant. The performance of the reactor can be greatly improved by means of proper design of catalyst layer thickness and through adjusting feed composition to minimize or reduce mass transfer limitations in the reactor. Finally, the criteria that can be used to distinguish between different mass transport and kinetics regimes in the reactor with a first-order reforming reaction were presented.

Metal hydride hydrogen storage is a hydrogen storage method based on the principle of chemical absorption. Featuring high volumetric hydrogen storage density and high safety, its potential applications in the field of hydrogen storage on ships have attracted significant attention. Against this background, there is a series of issues to be studied, such as material properties, reactor performance, thermal management systems, cost, etc. This paper categorizes metal hydride hydrogen storage technology, summarizes its working principle and research progress on its material properties, and introduces its applications on ships. Next, combined with the application environment and demands of hydrogen ships, the paper analyzes the technological and economic feasibility of the application of metal hydride hydrogen storage technology on ships. To meet the requirements of hydrogen ships for hydrogen storage capacity and release rate, research on marine metal hydride hydrogen storage systems is introduced, including hydrogen storage system performance research, hydrogen storage reactor structure, reactor structure optimization and design ideas for thermal management systems coupled with marine fuel cell and hydrogen storage systems. Finally, the research direction of marine metal hydride hydrogen storage systems is predicted and summarized.

A miniature nuclear reactor is desirable for deployment as a localized nuclear power station in support of a carbon-free power supply. Coupling aspects of proliferation-resistant fuel with natural burnable absorber loading are evaluated for once-through operation cycle performance to minimize the need for refueling and fuel shuffling operations. The incorporation of 0.075 wt.% 237Np provides favorable plutonium isotopic vectors throughout an operational lifetime of 5.5 years. providing 35 MWe. Core performance was assessed using a verification-by-comparison approach for core designs with or without 237Np and/or gadolinia burnable absorber. Burnup Monte Carlo calculations were performed via MCOS coupling of MCNP and ORIGEN to an achievable burnup of ~62.5 GWd/t. The results demonstrate a minimal penalty to reactor performance due to the addition of these materials as compared against the reference design. Coupling of a proliferation-resistant fuel concept with a uniform loading of natural gadolinia burnable absorber for LEU+ fuel (7.5 wt.% 235U/U UO2) provides favorable excess reactivity considerations with minimized concerns for additional residual waste and more uniform distribution of un-depleted 235U in discharged fuel assemblies.

A miniature nuclear reactor is desirable for deployment as a localized nuclear power station in support of a carbon-free power supply. Coupling aspects of proliferation-resistant fuel with natural burnable absorber loading are evaluated for once-through operation cycle performance to minimize the need for refueling and fuel shuffling operations. The incorporation of 0.075 wt.% 237Np provides favorable plutonium isotopic vectors throughout an operational lifetime of 5.5 years. providing 35 MWe. Core performance was assessed using a verification-by-comparison approach for core designs with or without 237Np and/or gadolinia burnable absorber. Burnup Monte Carlo calculations were performed via MCOS coupling of MCNP and ORIGEN to an achievable burnup of ~62.5 GWd/t. The results demonstrate a minimal penalty to reactor performance due to the addition of these materials as compared against the reference design. Coupling of a proliferation-resistant fuel concept with a uniform loading of natural gadolinia burnable absorber for LEU+ fuel (7.5 wt.% 235U/U UO2) provides favorable excess reactivity considerations with minimized concerns for additional residual waste and more uniform distribution of un-depleted 235U in discharged fuel assemblies. [ABSTRACT FROM AUTHOR]

The term "e-fuel" typically refers to synthetic fuels produced using renewable energy sources, primarily starting with green hydrogen. Hydrogen serves as the foundational e-fuel, but there are also proposed solutions involving combining hydrogen with carbon dioxide to produce e-fuels that resemble today's alkanes or alcohols. The production process integrates water electrolysis, CO₂ capture, and fuel synthesis, all powered by renewable sources like wind and solar energy. Key processes include hydrogen generation using various electrolyzers and CO₂ capture from either direct air capture or industrial sources. Subsequently, hydrogen and captured CO₂ are synthesized into hydrocarbons using methods such as Methanol Synthesis, Fischer-Tropsch Synthesis, and the Sabatier Process. Advances in catalyst technology, reactor design, and renewable energy integration are enhancing production efficiency and feasibility. Although currently more expensive than fossil fuels, e-fuels are expected to become cost-competitive with technological advancements and supportive policies. They offer significant environmental benefits, including carbon neutrality and reduced pollution. One crucial enabler of e-fuels is the development of novel combustion systems for internal combustion engines. Innovations such as direct injection and jet ignition improve combustion efficiency when using e-fuels. These systems enable optimized premixed or diffusion combustion, balancing efficiency and performance for both liquid and gaseous fuels resembling diesel or gasoline. E-fuels are poised to play a vital role in achieving a sustainable, low-carbon energy future, particularly in sectors where direct electrification is challenging. Continued research and policy support are essential for their further development, with direct injection and jet ignition systems playing an integral part in this transformative journey. [ABSTRACT FROM AUTHOR]

Parameter space for spherical tokamak reactors is explored quantitatively to elucidate the main constraints for spherical tokamak design choices. Using a constant plasma current Ip search constraint, a set of four Ip scenarios (5, 10, 15, and 20 MA) is first explored in a wide parameter space. Considering modest but gradually increasing auxiliary power, a set of four machine configurations (major radius $$R$$ R = 1.25, 1.75, 2.25, and 3.5 m) is explored next, optimizing the Ip and the bootstrap fraction. Constraints that narrow down the vast parameter space are elaborated along with critical assumptions, such as current drive efficiency, H-mode enhancement factor, nuclear shielding efficiency, and confinement scaling. Limits on the current density of the center post and how it affects the shielding are quantitatively indicated, thereby setting a lower limit on the aspect ratio. [ABSTRACT FROM AUTHOR]

An efficient and successful electrochemical process must take place in an electrochemical reactor with an adapted and optimized design that allows superior performance to be achieved. Traditional manufacturing methods have made the task of optimizing and adapting reactors very expensive. However, 3D printing allows prototypes to be built in a very short time and at a very low cost compared to traditional manufacturing techniques. This has caused research into new electrochemical reactors in different laboratories to skyrocket in recent years. The rapid evolution of 3D printing technology, as well as the appearance of new materials, have meant that they can be included in many applications, such as the electrochemical treatment of contaminated water or energy devices, batteries or fuel cells. In this review, the latest advances in the manufacture of electrochemical reactors and the main applications that have made use of them will be presented and critically discussed. [ABSTRACT FROM AUTHOR]

Ammonia (NH3) production is of global concern for today's food supply security and as future energy vector. Plasma technology can add to supply‐chain resilience of fertilizer production and improve the environmental profile using renewable energy; allowing distributed NH3 production. With the objective to provide process intensification of small‐capacity reactors for local supply, a novel micropyramid‐disk plasma reactor operated in micro‐arc mode was developed. NH3 was synthesized from N2, nitrogen, and H2, hydrogen over Ru/MCM‐41 catalyst at atmospheric pressure. The microplasma brings plasma and catalyst surface close together and intensifies the electric field. The arc plasma elevates temperature, 'nonthermal', releasing high‐energy free electrons, known to be effective in converting low‐reactive molecules. The study demonstrates that microplasma, with reduced electrode‐to‐electrode dimensions and a microstructured reaction environment, enhances the performance of the NH3 synthesis and opens novel process windows. This is detailed on the impact of feed ratio (N2/H2), applied voltage, frequency, electrode gap, and the flow distribution by which the gas is fed in. Optical emission spectroscopy (OES) was used to identify vibrationally and other excited species generated by the microplasma and confirms the catalyst is in symbiosis with the radicals. [ABSTRACT FROM AUTHOR]

[Display omitted] The potential for directly converting CO 2 to valuable liquid fuels utilizing green and renewable electricity has sparked significant interest in CO 2 electroreduction (CO 2 RR). In recent years, CO 2 conversion to formate/formic acid (HCOO−/HCOOH) has witnessed fast growth due to its economic and technological viability combined with the development of highly selective catalysts and practical electrolyzes. In this review, we summarize and discuss recent advances in HCOOH generation from CO 2 reduction in terms of (1) the rationale behind choosing HCOOH as a CO 2 electroreduction product, (2) mechanistic pathways to form HCOOH, (3) novel electrocatalyst developments for enhanced HCOOH production, and (4) electrolyzer designs that tackle practical challenges in scalability, reaction rate, and product impurities. Finally, a brief outlook on future opportunities in this field is offered to accelerate the industrialization of CO 2 RR to HCOOH. [ABSTRACT FROM AUTHOR]

Solar-boosted photo-technology stands out as a powerful strategy for photosynthesis and photocatalytic processes due to its minimal energy requirements, cost-effectiveness and operation under milder, environmentally friendly conditions compared to conventional thermocatalytic options. The design and development of photocatalysts have received a great deal of attention, whereas photoreactor development must be studied deeper to enable the design of efficient devices for practical exploitation. Furthermore, scale-up issues are important for this application, since light distribution through the photoreactor is a concurrent factor. This review represents a comprehensive study on the development of photoreactors to be used mainly for the photoreduction of CO2 to fuels, but with concepts easily transferable to other photosynthetic applications such as ammonia synthesis and water splitting, or wastewater treatment, photovoltaics combined to photoreactors, etc. The primary categories of photoreactors are thoroughly examined. It is also explained which parameters influence the design of a photoreactor and next-generation high-pressure photoreactors are also discussed. Last but not least, current technologies for solar concentrators are recalled, considering their possible integration within the photoreactor. While many reviews deal with photocatalytic materials, in the authors' view, photoreactors with significant scale and their merged devices with solar concentrators are still unexploited solutions. These are the key to boost the efficiency of these processes towards commercial viability; thus, the aim of this review is to summarise the main findings on solar photoreactors for the photoreduction of CO2 and for related applications. [ABSTRACT FROM AUTHOR]