The electrocatalytic reduction of CO2 has been investigated using four Cu‐based metal–organic porous materials supported on gas diffusion electrodes, namely, (1) HKUST‐1 metal–organic framework ...(MOF), Cu3(μ6‐C9H3O6)2n; (2) CuAdeAce MOF, Cu3(μ3‐C5H4N5)2n; (3) CuDTA mesoporous metal–organic aerogel (MOA), Cu(μ‐C2H2N2S2)n; and (4) CuZnDTA MOA, Cu0.6Zn0.4(μ‐C2H2N2S2)n. The electrodes show relatively high surface areas, accessibilities, and exposure of the Cu catalytic centers as well as favorable electrocatalytic CO2 reduction performance, that is, they have a high efficiency for the production of methanol and ethanol in the liquid phase. The maximum cumulative Faradaic efficiencies for CO2 conversion at HKUST‐1‐, CuAdeAce‐, CuDTA‐, and CuZnDTA‐based electrodes are 15.9, 1.2, 6, and 9.9 %, respectively, at a current density of 10 mA cm−2, an electrolyte‐flow/area ratio of 3 mL min cm−2, and a gas‐flow/area ratio of 20 mL min cm−2. We can correlate these observations with the structural features of the electrodes. Furthermore, HKUST‐1‐ and CuZnDTA‐based electrodes show stable electrocatalytic performance for 17 and 12 h, respectively.
Closing the loop: Metal–organic porous materials are effective electrocatalysts for the continuous electrochemical conversion of CO2 to alcohols, a process that could promote the transition to a low‐carbon economy. The modularity of these systems yields many opportunities for further performance improvements and opens new directions in electrocatalysis.
The development of electrochemical processes for using captured CO
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in the production of valuable compounds appears as an attractive alternative to recycle CO
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and, at the same time, to store ...electricity from intermittent renewable sources. Among the different innovative attempts that are being investigated to improve these processes, the application of ionic liquids (ILs) has received growing attention in recent years. This paper presents a unified discussion of the significant work that involves the utilisation of ILs for the valorisation of CO
2
by means of electrochemical routes. We discuss studies in which CO
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is used as one of the reactants to electrosynthesise value-added products, among which dimethyl carbonate has been the focus of particular attention in the literature. Approaches based on the electrochemical reduction of CO
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to convert it into products without the use of other carbon-based reactants are also reviewed, highlighting the remarkable improvements that the use of ILs has allowed in the CO
2
electroreduction to CO. The review emphasises on different aspects related to process design, including the nature of IL anions and cations that have been used, the working conditions, the electrocatalytic materials, the electrode configurations, or the design of electrochemical cells, as well as discussing the most relevant observations, results and figures of merit that the participation of ILs has allowed to achieve in these processes. Several conclusions are finally proposed to highlight crucial challenges and recommendations for future research in this area.
This work reviews the use of ionic liquids in electrochemical approaches for the valorisation of CO
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into value-added products, highlighting the beneficial role that ionic liquids can play in improving CO
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electrovalorisation processes.
Ionic liquids have attracted a lot of attention as potential replacements for conventional volatile organic solvents, although they may pose environmental risks to aquatic ecosystems that have to be ...assessed. There is strong interest in developing mathematical models to estimate the ecotoxicity of ionic liquids, minimising the experimental investigations and the consequent consumption of time and resources. This paper presents a new approach for estimating the ecotoxicity of ILs, based on the standardised assay with the bacterium Vibrio fischeri, by means of the application of Partial Least Squares-Discriminant Analysis (PLS-DA). The PLS-DA model developed makes it possible to discriminate ionic liquids, formed by combinations of 30 anions and 64 cations, on the basis of their expected toxicity with respect to conventional solvents that they may replace. The successful results obtained in the validation of the model reveal that this approach can be useful as a screening tool to easily aid, from the early stages of the process, the design of aquatic environmentally friendly ionic liquids. This approach may also be useful for the further development of predictive models based on other aquatic organisms, for which more data are expected to be available in the near future.
Green hydrogen—a carbon-free renewable fuel—has the capability to decarbonise a variety of sectors. The generation of green hydrogen is currently restricted to water electrolysers. The use of ...freshwater resources and critical raw materials, however, limits their use. Alternative water splitting methods for green hydrogen generation via photocatalysis and photoelectrocatalysis (PEC) have been explored in the past few decades; however, their commercial potential still remains unexploited due to the high hydrogen generation costs. Novel PEC-based simultaneous generation of green hydrogen and wastewater treatment/high-value product production is therefore seen as an alternative to conventional water splitting. Interestingly, the organic/inorganic pollutants in wastewater and biomass favourably act as electron donors and facilitate the dual-functional process of recovering green hydrogen while oxidising the organic matter. The generation of green hydrogen through the dual-functional PEC process opens up opportunities for a “circular economy”. It further enables the end-of-life commodities to be reused, recycled and resourced for a better life-cycle design while being economically viable for commercialisation. This review brings together and critically analyses the recent trends towards simultaneous wastewater treatment/biomass reforming while generating hydrogen gas by employing the PEC technology. We have briefly discussed the technical challenges associated with the tandem PEC process, new avenues, techno-economic feasibility and future directions towards achieving net neutrality.
Abstract
The doping of zirconium based EHU-30 and EHU-30-NH
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metal–organic frameworks with copper(II) yielded a homogeneous distribution of the dopant with a copper/zirconium ratio of 0.04–0.05. The ...doping mechanism is analysed by chemical analysis, microstructural analysis and pair distribution function (PDF) analysis of synchrotron total scattering data in order to get deeper insight into the local structure. According to these data, the Cu(II) atoms are assembled within the secondary building unit by a transmetalation reaction, contrarily to UiO-66 series in which the post-synthetic metalation of the MOF takes place through chemical anchorage. The resulting materials doubled the overall performance of the parent compounds for the CO
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electroreduction, while retained stable the performance during continuous transformation reaction.
Shipping is a very important source of pollution worldwide. In recent years, numerous actions and measures have been developed trying to reduce the levels of greenhouse gases (GHG) from the marine ...exhaust emissions in the fight against climate change, boosting the Sustainable Development Goal 13. Following this target, the action of hydrogen as energy vector makes it a suitable alternative to be used as fuel, constituting a very promising energy carrier for energy transition and decarbonization in maritime transport. The objective of this study is to develop an ex-ante environmental evaluation of two promising technologies for vessels propulsion, a H2 Polymeric Electrolytic Membrane Fuel Cell (PEMFC), and a H2 Internal Combustion Engine (ICE), in order to determine their viability and eligibility compared to the traditional one, a diesel ICE. The applied methodology follows the Life Cycle Assessment (LCA) guidelines, considering a functional unit of 1 kWh of energy produced. LCA results reveal that both alternatives have great potential to promote the energy transition, particularly the H2 ICE. However, as technologies readiness level is quite low, it was concluded that the assessment has been conducted at a very early stage, so their sustainability and environmental performance may change as they become more widely developed and deployed, which can be only achieved with political and stakeholder's involvement and collaboration.
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•LCA of hydrogen propulsion technologies for shipping was developed.•H2 engine presented the lowest environmental impacts.•The analysis was conducted in a very early degree of maturity of the devices.•LCA proves to be a useful and key tool for moving towards sustainability.•Policy implication is mandatory to achieve decarbonization in shipping.
Limitations of the FA conventional process can include slow reaction rate, undesirable by-products, high cost of investment, and issues related to the environment such as the high energy requirements ...(in the separation stage) and a noticeable dependence on fossil fuel (heavy fuel oil is used in the synthesis of CO) 4. ...in parallel to the alarming issue of the global warming and climate change, the depletion of the mentioned fossil fuels, which must remain underground for generations to come, may seem less evident. ...it is not surprising that nowadays the utilization of CO2 is gaining momentum in the scientific community and the industrial corporations in order to shift from conventional fossil-based processes toward environmentally-friendly processes. ...during the past decades, efforts have focused on the development of metal catalyst. ...an efficient mode of operation of the electrolytic reactor, such as recirculation mode, is necessary to achieve at least an FA concentration of 20% wt. to obtain an even CF compared to the FA conventional process. 4.
Climate change has become one of the most important challenges in the 21st century, and the electroreduction of CO2 to value-added products has gained increasing importance in recent years. In this ...context, formic acid or formate are interesting products because they could be used as raw materials in several industries as well as promising fuels in fuel cells. Despite the great number of studies published in the field of the electrocatalytic reduction of CO2 to formic acid/formate working with electrocatalysts of different nature and electrode configurations, few of them are focused on the comparison of different electrocatalyst materials and electrode configurations. Therefore, this work aims at presenting a rigorous and comprehensive comparative assessment of different experimental data previously published after many years of research in different working electrode configurations and electrocatalysts in a continuous mode with a single pass of the inputs through the reactor. Thus, the behavior of the CO2 electroreduction to formate is compared operating with Sn and Bi-based materials under Gas Diffusion Electrodes (GDEs) and Catalyst Coated Membrane Electrodes (CCMEs) configurations. Considering the same electrocatalyst, the use of CCMEs improves the performance in terms of formate concentration and energy consumption. Nevertheless, higher formate rates can be achieved with GDEs because they allow operation at higher current densities of up to 300 mA·cm−2. Bi-based-GDEs outperformed Sn-GDEs in all the figures of merit considered. The comparison also highlights that in CCME configuration, the employ of Bi-based-electrodes enhanced the behavior of the process, increasing the formate concentration by 35% and the Faradaic efficiency by 11%.
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•A two-step eco-efficiency methodology combining LCA an LCC was developed.•A eco-efficient index was defined coupling LCA-LCC results to linear programming.•Three origins for anchovy ...species were evaluated under cradle to gate approach.•The application of circular economy improved the environmental and economic benefit.•The method proposed facilitated the decision-making in the anchovy canning sector.
The production of food that is environmentally friendly and presents a high economic return is one of the current concerns for the food industry. Eco-efficiency links the environmental performance of a product to its economic value. In this context, this study combines Life Cycle Assessment (LCA) and Life Cycle Costing (LCC) to propose a two-step eco-efficiency methodology assessment for the fish canning industry. An eco-label rating system based on a descriptive weighting of environmental (Global Warming Potential, Acidification Potential, Eutrophication Potential and the ReCiPe Single Score Endpoint) and economic (Value Added) indicators was applied to the canned anchovy. Secondly, LCA-LCC results were coupled to linear programming (LP) tools in order to define a composite eco-efficiency index. This approach enables translation into economic terms of the environmental damage caused when a given alternative is chosen. In particular, different origins for anchovy species (South American vs. Cantabrian) and related waste management alternatives (landfill, incineration and valorization) were evaluated under this cradle to gate approach. Results indicated that substantial differences can be observed depending on the origin of the fish. Anchovies landed in Cantabria show a higher value added score at the expense of larger environmental impacts, mainly due to fuel use intensity. Moreover, its environmental scores are lowered when fish residues are valorized into marketable products, while increasing the value added. This study demonstrates the environmental and economic benefits of applying circular economy. According to this, it is possible to introduce the cradle-to-cradle concept in the fish canned industry. The methodology proposed is intended to be useful to decision-makers in the anchovy canning sector and can be applied to other regions and industrial sectors.
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