Explore the vast range of titles available.

This research focuses on the rational design of porous enzymatic electrodes, using horseradish peroxidase (HRP) as a model biocatalyst. Our goal was to identify the main obstacles to maximizing biocatalyst utilization within complex porous structures and to assess the impact of various carbon nanomaterials on electrode performance. We evaluated as-synthesized carbon nanomaterials, such as Carbon Aerogel, Coral Carbon, and Carbon Hollow Spheres, against the commercially available Vulcan XC72 carbon nanomaterial. The 3D electrodes were constructed using gelatin as a binder, which was cross-linked with glutaraldehyde. The bioelectrodes were characterized electrochemically in the absence and presence of 3 mM of hydrogen peroxide. The capacitive behavior observed was in accordance with the BET surface area of the materials under study. The catalytic activity towards hydrogen peroxide reduction was partially linked to the capacitive behavior trend in the absence of hydrogen peroxide. Notably, the Coral Carbon electrode demonstrated large capacitive currents but low catalytic currents, an exception to the observed trend. Microscopic analysis of the electrodes indicated suboptimal gelatin distribution in the Coral Carbon electrode. This study also highlighted the challenges in transferring the preparation procedure from one carbon nanomaterial to another, emphasizing the importance of binder quantity, which appears to depend on particle size and quantity and warrants further studies. Under conditions of the present study, Vulcan XC72 with a catalytic current of ca. 300 µA cm−2 in the presence of 3 mM of hydrogen peroxide was found to be the most optimal biocatalyst support.

Acetogenic bacteria produce CO2‐based chemicals in aqueous media by hydrogenotrophic conversion of CO2, but CO is the preferred carbon and electron source. Consequently, coupling CO2 electrolysis with bacterial fermentation within an integrated bio‐electrocatalytical system (BES) is promising, if CO2 reduction catalysts are available for the generation of CO in the complex biotic electrolyte. A standard stirred‐tank bioreactor was coupled to a zero‐gap PEM electrolysis cell for CO2 conversion, allowing voltage control and separation of the anode in one single cell. The cathodic CO2 reduction and the competing hydrogen evolution enabled in‐situ feeding of C. ragsdalei with CO and H2. Proof‐of‐concept was demonstrated in first batch processes with continuous CO2 gassing, as autotrophic growth and acetate formation was observed in the stirred BES in a voltage range of −2.4 to −3.0 V. The setup is suitable also for other bioelectrocatalytic reactions. Increased currents and lower overvoltages are however required. Atomically‐dispersed M−N−C catalysts show promise, if degradation throughout autoclaving can be omitted. The development of selective and autoclavable catalysts resistant to contamination and electrode design for the complex electrolyte will enable efficient bioelectrocatalytic power‐to‐X systems based on the introduced BES. By integration of a PEM electrolysis single cell to the bottom of a stirred tank bioreactor, an integrated bio‐electrocatalytic system (BES) was developed. The BES allows control of potential, pH and temperature with an online‐detection of product formation rates. Proof‐of‐concept was shown for the CO2/H2O PEM electrolysis to feed acetogenic C. ragsdalei with syngas to produce acetate.

Inorganic salt melts are used for the preparation of ceramics. It turns out that such ionothermal syntheses can also be employed in the chemistry of carbon. Carbon materials with improved application-relevant properties such as high surface area and large pore volume can be obtained. The way these properties are obtained strongly reminds on classic sol–gel synthesis, which displays a comparably easy approach toward such porous carbons. The central role of the solvent, i.e., the inorganic salt melt allows for variation of the chemical and morphological structure of carbon products. Interestingly, the use of inorganic salt melts may also give insights into the crystallization of carbon, if precursors are directly added to the hot melt, which additionally guarantees reorganizational dynamics to the pyrolysis intermediates. Graphical Abstract

The stability of Fe−N−C oxygen reduction reaction (ORR) electrocatalysts has been considered a primary challenge for their practical application in proton exchange membrane fuel cells (PEMFCs). While several studies have attempted to reveal the possible degradation mechanism of Fe−N−C ORR catalysts, there are few research results reporting on their stability as well as the possible Fe species formed under different voltages in real PEMFC operation. In this work, we employ in‐situ X‐ray absorption near‐edge structure (XANES) to monitor the active‐site degradation byproducts of an atomically dispersed Fe−N−C ORR catalyst under a H2/O2‐operating PEMFC at 90 % relative humidity and 80 °C. For this, stability tests were carried out at two constant cell voltages, namely 0.4 and at 0.8 V. Even though the ORR activity of the Fe−N−C catalyst decreased significantly and was almost identical at the end of the tests for the two voltages employed, the analysis of the XANES recorded under H2/N2 configuration at 0.6 and 0.9 V within the stability test suggests that two different degradation mechanisms occur. They are demetalation of iron cations followed by their precipitation into Fe oxides upon operation at 0.8 V, versus a chemical carbon oxidation close to the active sites, likely triggered by reactive oxygen species (ROS) originated from the H2O2 formation, during the operation at 0.4 V. In situ XAS of an Fe−N−C catalyst in Proton Exchange Membrane Fuel Cell suggests two different degradation mechanisms: demetalation of Fe cations followed by their precipitation into Fe oxides upon operation at 0.8 V, and chemical carbon oxidation close to the active sites, triggered by reactive oxygen species (ROS) originated from H2O2 formation, upon operation at 0.4 V.

Metal‐nitrogen/carbon (M‐N/C) catalysts, particularly those incorporating Fe, Co, or Mn, are among the most promising non‐platinum group catalysts for the acidic oxygen reduction reaction (ORR) in fuel cells. This study reports a Co‐N/C catalyst featuring high (3 wt%) cobalt content exclusively present as atomic sites. Extended X‐ray absorption fine structure analysis confirms a tetrapyridinic Co‐N4 coordination environment in the optimized (3.0)Co‐N/CΔ catalyst. The high cobalt loading leads to a significant density of electrochemically accessible active sites, 3.58 × 1019 sites g−1, quantified via the nitrite stripping method. The catalyst demonstrates excellent ORR activity in a rotating ring‐disk electrode setup, achieving a half‐wave potential (E1/2) of 0.76 V at a low loading of 0.2 mg cm−2 and a mass activity of 3.5 A g−1 at 0.80 VRHE. Single‐cell hydrogen‐oxygen PEMFC tests achieve a peak power density exceeding 1.3 W cm−2 (iR‐corrected). Under hydrogen‐air condition, the catalyst delivers 0.54 A cm−2 at 0.60 V (0.39 W cm−2). Despite the intrinsically higher turnover frequency of Fe‐based sites, the optimized (3.0)Co‐N/CΔ catalyst achieves similar fuel cell performance to that of Fe‐N/C, highlighting the critical role of site density in overall activity. Cobalt‐based platinum‐metal free catalysts can compete with iron‐based materials as catalysts on the cathodes of fuel cells due to their high site density and activity. This discovery highlights the importance of understanding the active sites responsible for the catalytic activity in these non‐precious metal catalysts.

In this study we demonstrate a cheap and sustainable ammonothermal approach towards nitrogen-doped porous carbons. Sodium borate (borax) is employed as a catalyst during the synthesis resulting in the formation of small interconnected primary particles of <100 nm in size. Microporosity is created in these nitrogen-doped, ammonothermal carbon samples by a synchronous activation and post carbonization procedure at 850 °C, while the interconnected primary particles offer larger interstitial void spaces including mesopores. Variation of the starting ammonia concentration allows for the facile adjustment of the final nitrogen content, reaching up to 7 wt.% after post carbonization. Electrochemical characterization is carried out in two and three electrode modes by means of cyclic voltammetry and galvanostatic cycling at different scan rates and current densities, respectively. The sample prepared at a high glucose-to-ammonia ratio shows high specific capacitance of 185 and 144 F g −1 at 0.2 and 20 A g −1 , respectively (271 F g −1 in a three electrode mode at 1 A g −1 ). All samples demonstrate a very stable capacitance over the tested 5000 cycles at 10 A g −1 with no degradation and an excellent coulombic efficiency of >99%. Comparison of different pore systems indicates that a continuous pore size distribution may explain improved rate performances. A sol-gel-type ammonothermal carbonization of sugar, catalyzed by Borax was combined with physical CO 2 -activation to obtain well-performing and sustainable electrode materials for aqueous supercapacitors Highlights Porous nitrogen-doped carbon was synthesized by ammonothermal carbonization High capacitances of 185 F g −1 were obtained Very high cycling stability was obtained

Hard carbons are promising candidates for high-capacity anode materials in alkali metal-ion batteries, such as lithium- and sodium-ion batteries. High reversible capacities are often coming along with high irreversible capacity losses during the first cycles, limiting commercial viability. The trade-off to maximize the reversible capacities and simultaneously minimizing irreversible losses can be achieved by tuning the exact architecture of the subnanometric pore system inside the carbon particles. Since the characterization of small pores is nontrivial, we herein employ Kr, N 2 and CO 2 gas sorption porosimetry, as well as H 2 O vapor sorption porosimetry, to investigate eight hard carbons. Electrochemical lithium as well as sodium storage tests are compared to the obtained apparent surface areas and pore volumes. H 2 O, and more importantly CO 2 , sorption porosimetry turned out to be the preferred methods to evaluate the likelihood for excessive irreversible capacities. The methods are also useful to select the relatively most promising active materials within chemically similar materials. A quantitative relation of porosity descriptors to the obtained capacities remains a scientific challenge.

Pore size analysis is essential for understanding and optimizing structure-performance relations of functional carbon-based materials including activated carbons, supercapacitor electrodes and atomically dispersed metal-nitrogen-doped carbon (M-N-C) catalysts. Pore size distribution (PSD) plots based on gas sorption porosimetry often show narrow micropores that are related to the adsorptive properties of named materials, which must be considered as artefacts arising from approximations in classical density functional theory (cDFT) models. By selectively preparing specific in-plane functionalities using pyrolytic template-ion (salt templating) reactions, we herein show that those apparent pores can be explained by preferential adsorption of the adsorbate molecules to specific in-plane functionalities. Tetrapyrrolic Zn-N sites are present in ZIF-8 derived carbons, which are converted by Zn-extraction into nitrogen-doped carbons (NDC) comprising tetrapyrrolic H N sites. DFT-based calculation of adsorption energies allows the conclusive assignment of corresponding adsorption phenomena in comparative N vs. CO vs. Ar adsorption measurements additionally using Langmuir analysis. While the assignment of artefacts may improve the discussion of porosity, the determination of specific adsorption sites may be utilized as a valuable tool in materials science. Advanced models for the important material classes may allow accelerated progress in important energy-related research fields.

Acetogenic bacteria produce CO 2 ‐based chemicals in aqueous media by hydrogenotrophic conversion of CO 2 , but CO is the preferred carbon and electron source. Consequently, coupling CO 2 electrolysis with bacterial fermentation within an integrated bio‐electrocatalytical system (BES) is promising, if CO 2 reduction catalysts are available for the generation of CO in the complex biotic electrolyte. A standard stirred‐tank bioreactor was coupled to a zero‐gap PEM electrolysis cell for CO 2 conversion, allowing voltage control and separation of the anode in one single cell. The cathodic CO 2 reduction and the competing hydrogen evolution enabled in‐situ feeding of C. ragsdalei with CO and H 2 . Proof‐of‐concept was demonstrated in first batch processes with continuous CO 2 gassing, as autotrophic growth and acetate formation was observed in the stirred BES in a voltage range of −2.4 to −3.0 V. The setup is suitable also for other bioelectrocatalytic reactions. Increased currents and lower overvoltages are however required. Atomically‐dispersed M−N−C catalysts show promise, if degradation throughout autoclaving can be omitted. The development of selective and autoclavable catalysts resistant to contamination and electrode design for the complex electrolyte will enable efficient bioelectrocatalytic power‐to‐X systems based on the introduced BES.

Over the past 150 years, our ability to produce and transform engineered materials has been responsible for our current high standards of living, especially in developed economies. However, we must carefully think of the effects our addiction to creating and using materials at this fast rate will have on the future generations. The way we currently make and use materials detrimentally affects the planet Earth, creating many severe environmental problems. It affects the next generations by putting in danger the future of the economy, energy, and climate. We are at the point where something must drastically change, and it must change now. We must create more sustainable materials alternatives using natural raw materials and inspiration from nature while making sure not to deplete important resources, i.e. in competition with the food chain supply. We must use less materials, eliminate the use of toxic materials and create a circular materials economy where reuse and recycle are priorities. We must develop sustainable methods for materials recycling and encourage design for disassembly. We must look across the whole materials life cycle from raw resources till end of life and apply thorough life cycle assessments (LCAs) based on reliable and relevant data to quantify sustainability. We need to seriously start thinking of where our future materials will come from and how could we track them, given that we are confronted with resource scarcity and geographical constrains. This is particularly important for the development of new and sustainable energy technologies, key to our transition to net zero. Currently 'critical materials' are central components of sustainable energy systems because they are the best performing. A few examples include the permanent magnets based on rare earth metals (Dy, Nd, Pr) used in wind turbines, Li and Co in Li-ion batteries, Pt and Ir in fuel cells and electrolysers, Si in solar cells just to mention a few. These materials are classified as 'critical' by the European Union and Department of Energy. Except in sustainable energy, materials are also key components in packaging, construction, and textile industry along with many other industrial sectors. This roadmap authored by prominent researchers working across disciplines in the very important field of sustainable materials is intended to highlight the outstanding issues that must be addressed and provide an insight into the pathways towards solving them adopted by the sustainable materials community. In compiling this roadmap, we hope to aid the development of the wider sustainable materials research community, providing a guide for academia, industry, government, and funding agencies in this critically important and rapidly developing research space which is key to future sustainability.