Metals play a vital role in many industries, but their extraction through traditional mining methods poses significant environmental challenges. To address these issues, alternative sources such as coal fly ash (CFA) need to be explored for the recovery of transition metals. In this study, we describe a novel green strategy for the selective separation and recovery of valuable metal ions from complex solutions using semi-synthetic proteins. Myoglobin (Mb), a small protein available from renewable sources, was conjugated to the high-affinity metal chelator SG-20 to create the semi-synthetic protein Mb-SG-20. Mb-SG-20 was characterized by gel electrophoresis, mass spectrometry, and proteomic analysis and found to contain a distribution of 4–7 equiv of SG-20 conjugated to Mb surface lysine residues. Binding and recovery properties of Mb-SG-20 for nickel (Ni) and copper (Cu) ions were characterized. The results showed that Mb-SG-20 captures super-stoichiometric amounts of Ni or Cu while maintaining a strong affinity for Ni or Cu ions. Furthermore, we demonstrate the recyclability of Mb-SG-20 as a Ni and Cu ion capture agent and provide proof-of-concept experiments using CFA leachate solution. This study presents a promising approach for the sustainable recovery of valuable metals from non-traditional sources, such as CFA.

Highly active and durable electrocatalysts for the cathodic oxygen reduction reaction (ORR) are vital for the large-scale commercialization of proton exchange membrane fuel cells. Alloying Pt with transition metals is a promising method to enhance the ORR catalytic activity, but the leaching of transition metals is inevitable, which deteriorates the stability. Here, we report the design of a P-doped PtCo electrocatalyst supported on carbon via a facile one-pot hydrothermal method. On the one hand, the introduction of P into the carbon support by phytic acid can enhance the anchoring ability of the PtCo alloy and inhibit the migration of nanoparticles. On the other hand, the doping of P into the lattice of the PtCo alloy further tunes the electronic effect, which improves activity and stability simultaneously. The mass activity of as-prepared P5-PtCo/C at 0.9 V can reach 0.72 A mgPt–1, which is 4.5 times higher than that of commercial Pt/C. After an accelerated durability test (ADT) of 30,000 potential cycles, the mass activity only decreased by 9.4%. Meanwhile, the average particle size of the catalyst slightly increased from 4.94 to 5.15 nm after the ADT of 70,000 potential cycles. This study provides a facile approach for constructing nonmetal-doped PtM catalysts with improved durability for the ORR.

Although the Zn-air battery has many advantages, its short practical life hinders its development. Many solutions have been proposed and extensively studied. In this paper, a cobalt-nitrogen co-doped hierarchical porous carbon-based bifunctional catalyst (Co/N-HPCs-800) is reported, using sustainable and low-cost sodium alginate (Na-Alg), a common seaweed extract, as a precursor to complex excess metal particles. The hydrogel network formed by the exchange of sodium ions with metal cation (Co2+) ions is the key to the controllable synthesis of highly dispersed metal atoms. Co/N-HPCs-800 shows excellent catalytic performance and durability in oxygen reduction reaction (E1/2 = 0.86 V) and oxygen evolution reaction (367 mV @ 10 mA cm–2). Importantly, we only attenuated the half-wave potential by 8 mV after more than 50,000 cycles. In addition, the Zn-air batteries (ZABs) using Co/N-HPCs-800 as a cathode exhibit a power density up to 159.67 mW cm–2 and a high specific capacity of 787.94 mA h g–1. This work opens up practical new strategies for synthesizing excess metal catalysts in low cost, effectively improving the service life of Zn-air batteries.

Molten alkali metal borates are a class of molten salts that have recently shown promise as high-temperature sorbents for capture of CO2 and other acid gases. Thermal swing systems based on molten borates have demonstrated CO2 capture capacities greater than those of amines, enabling efficient recovery of high-temperature heat in flue gas without practical concerns commonly associated with solid sorbents at these temperatures. In this work, we exploited generation of carbonates upon CO2 capture by borates to enable their use as electrolytic media for carbon nanotube (CNT) synthesis by CO2 splitting. Here, we report the conditions necessary to synthesize valuable multiwalled CNTs by CO2 capture and conversion as a sustainable alternative to conventional carbon-intensive CNT synthesis techniques. Effects of cathode materials and operating conditions are quantified in sodium lithium borate, achieving significantly higher CO2 uptake capacities than alkali metal carbonate salts for conversion of CO2 into CNTs in the 550–650 °C range.

Electrochemical nitrate reduction as to recover valuable ammonia (NH4+/NH3) from nitrogen-contaminated waters is a promising alternative to the Haber–Bosch synthesis. Characteristics of two bimetallic electrodes, RhxCu1–x/Ni and RhxSn1–x/Ni, was investigated on the formation of ammonia from the nitrate reduction reaction (NO3–RR) in neutral media. Results of voltammetry showed that in bimetallic electrodes, Rh promoted the step of NO2– to NH4+ at a potential region which the faradaic current overlapped that of redox transformation of the supported metals, i.e., Cu(0)/Cu(I) and Sn(0)/Sn(II). Rh as the adsorption site controlled the rate-limiting NO3– to the NO2– step, thereby enhancing the current response of nitrate reduction. The loading percentage of Rh critically affected the conversion of intermediates NO2– and N2 to ammonia on Cu and Sn metals, respectively. Both the selectivity and faradaic efficiency achieved above 98% at the best Rh to Cu ratio of 1:4, i.e., Rh0.2Cu0.8/Ni at −1.4 V (vs Ag/AgCl). The specific ammonia yield rate of 3.5 mg-N h–1 g–1 in 0.05 M of KNO3 solution was obtained. However, at higher applied current density, N2 primarily formed on the Sn site competed the formation of NH4+ on the Rh site of the Rh0.5Sn0.5/Ni electrode.

Atmospheric water harvesting is a sustainable solution to global water shortage, which requires high efficiency, high durability, low cost, and environmentally friendly water collectors. In this paper, we report a novel water collector design based on a nature-inspired hybrid superhydrophilic/superhydrophobic aluminum surface. The surface is fabricated by combining laser and chemical treatments. We achieve a 163° contrast in contact angles between the superhydrophilic pattern and the superhydrophobic background. Such a unique superhydrophilic/superhydrophobic combination presents a self-pumped mechanism, providing the hybrid collector with highly efficient water harvesting performance. Based on simulations and experimental measurements, the water harvesting rate of the repeating units of the pattern was optimized, and the corresponding hybrid collector achieves a water harvesting rate of 0.85 kg m–2 h–1. Additionally, our hybrid collector also exhibits good stability, flexibility, as well as thermal conductivity and hence shows great potential for practical application.

Fire accidents can trigger severe personal injury and large-scale property damage. Therefore, the use of flame retardant is essential. A novel green ternary nanocomposite intumescent flame retardant (IFR) (CNC@MEL-PA) was fabricated by successively modifying the gas source melamine (MEL) and acid source phytic acid (PA) on the carbon source cellulose nanocrystals (CNCs). CNC@MEL-PA exhibited better thermal stability, carbon layer formation ability, and smoke suppression efficiency due to its characteristic two-dimensional (2D) petal structure and intumescent carbon layer. Notably, compared to CNCs, the expanded carbon layer volume of CNC@MEL-PA was enhanced from about 62.2 to 169.6 mm3. Therefore, this study provides a facile synthetic route of high-performance CNC@MEL-PA with good smoke suppression efficiency for a green flame-retardant material for construction and transportation products.

Non-oxidative ethanol dehydrogenation is a renewable source of acetaldehyde and hydrogen. The reaction is often catalyzed by supported copper catalysts with high selectivity. The activity and long-term stability depend on many factors, including particle size, choice of support, doping, etc. Herein, we present four different synthetic pathways to prepare Cu/SiO2 catalysts (∼2.5 wt % Cu) with varying copper distribution: hydrolytic sol–gel (sub-nanometer clusters), dry impregnation (A̅ = 3.4 nm; σ = 0.9 nm and particles up to 32 nm), strong electrostatic adsorption (A̅ = 3.1 nm; σ = 0.6 nm), and solvothermal hot injection followed by Cu particle deposition (A̅ = 4.0 nm; σ = 0.8 nm). All materials were characterized by ICP-OES, XPS, N2 physisorption, STEM-EDS, XRD, RFC N2O, and H2-TPR and tested in ethanol dehydrogenation from 185 to 325 °C. The sample prepared by hydrolytic sol–gel exhibited high Cu dispersion and, accordingly, the highest catalytic activity. Its acetaldehyde productivity (2.79 g g–1 h–1 at 255 °C) outperforms most of the Cu-based catalysts reported in the literature, but it lacks stability and tends to deactivate over time. On the other hand, the sample prepared by simple and cost-effective dry impregnation, despite having Cu particles of various sizes, was still highly active (2.42 g g–1 h–1 acetaldehyde at 255 °C). Importantly, it was the most stable sample out of the studied materials. The characterization of the spent catalyst confirmed its exceptional properties: it showed the lowest extent of both coking and particle sintering.

Dynamic covalent polymer networks represent new opportunities in the design of sustainable epoxy resins due to their excellent malleability and reprocessability; however, the adaptable network is usually accompanied by low glass transition temperature, poor creep resistance, and mechanical brittleness. Herein, we demonstrate a vanillin-based hyperbranched epoxy resin (VEHBP) containing disulfide and imine dynamic covalent bonds for recyclable and malleable epoxy resin with high glass transition temperature (Tg), significantly improved creep resistance, and mechanical properties. The dynamic covalent epoxy resin containing 5%VEHBP exhibited a high glass transition temperature of 175 °C and a creep temperature of 130 °C and a 34.1, 19.7, and 173.3% increase in tensile strength, storage modulus, and tensile toughness respectively, compared with the neat resin. Meanwhile, the hyperbranched topological structure of VEHBP complemented by dual dynamic bonds endowed these materials with excellent self-healing ability, reprocessability, and degradability, which represents an important step toward the design and fabrication of high-performance epoxy covalent adaptable networks.

Unbalanced fermentation is a promising innovative strategy for biotechnological production processes. Guided by the genome-scale metabolic network iLJ1162, the central carbon metabolism was rewired to enhance the synthesis of (3R)-acetoin and link it to establish efficient extracellular electron transfer through unbalanced fermentation in Shewanella oneidensis. We first successfully constructed an engineered strain using glycerol as the sole carbon source to coproduce (3R)-acetoin and bioelectricity. Key engineering targets for (3R)-acetoin synthesis and bioelectricity were predicted by iLJ1162, including the glycolysis module (gapA and pgk), the serine bypass module (glyA, serA, serB, and serC), and the pyruvate fermentation module (fdh). As a result, we discovered that the serB gene was conducive to the production of bioelectricity (35.91 ± 1.04 mW m–2), and serC promoted the synthesis of (3R)-acetoin (213.5 ± 6.07 mg L–1) in the serine bypass module. However, the low power output capacity became the bottleneck, limiting the acetoin yield. To further balance the reducing force, we developed functional electrodes composed of carbon nanotubes and graphene oxide, as well as electron shuttles for improving electricity generation. The power density and the titer of (3R)-acetoin, respectively, reached up to 149.72 ± 2.72 mW m–2 and 313.61 ± 5.48 mg L–1, which were 5.08 and 1.00 times higher than in the control. The optical purity of the resulting (3R)-acetoin surpassed 90%. This study provides a new paradigm for achieving the “balance” between high value-added products with low reducibility and electricity production in unbalanced fermentation while boosting the titer of products based on model guidance.

In this paper, a potential method for the closed-loop recovery and regeneration of cathode materials from spent lithium-ion batteries (LIBs) is developed to greatly simplify the regeneration process, which successfully removes metal impurities from spent LIBs and synthesis of layered oxide LiNi1/3Co1/3Mn1/3O2 materials. First, the valuable metals (Ni, Co, Mn, and Li) in spent LIB materials are transformed into water-soluble ions based on the synergy between dl-malic acid and glucose. Subsequently, the residual Fe impurities are successfully decreased from the leaching solution by oxidation-precipitation. Prior to the synthesis process, valuable metal ions are immediately precipitated using oxalic acid as a precipitant from the leaching solution into Ni1/3Co1/3Mn1/3C2O4·nH2O with extremely uniform size particles. Furthermore, the LiNi1/3Co1/3Mn1/3O2 materials with an excellent crystal structure are successfully synthesized by adding Li2CO3 as the lithium source after roasting at 500 °C for 4 h and then at 950 °C for 12 h. The regenerated LiNi1/3Co1/3Mn1/3O2 materials demonstrate reliable electrochemical performance. This work clarifies a potential method for the closed-loop recovery resource sustainability of spent LIB materials.

Efficient strategies (degradation or recycling) for converting multifarious plastic wastes are imperative due to the resulting detriments to the environment and human life. With this in mind, the versatile and sulfur-mediated conversion of plastic wastes into value-added adsorbents is presented. The essential sulfur medium promotes the thermal polycondensation of polymer chains and leads to an impressive carbonization yield of 91%, significantly exceeding the control process without sulfur (0–12%). The final sublimation of sulfur endowed carbon materials with high porosity (SBET up to 888 cm2/g), while the attack of sulfur radicals naturally results in a high sulfur content (8.66–12.08%) of the carbon framework. Interestingly, the polar interactions (CO2 with sulfoxides, sulfones, and sulfonic) ensured the S-doped carbon good performance in CO2 adsorption (up to 4.6 mmol/g at 273 K), while the coordinating role of the sulfide group contributed to the heavy metal adsorption [removal efficiency of 99.5% for Pb(II) and 99.8% for Cd(II)].

Carbon dioxide makes the hydrogen combustion process unstable and destructive, thus affecting the efficiency and effectiveness of hydrogen energy use. Thus, it is very important to monitor CO2 in hydrogen gas. All-inorganic perovskites are used for optical sensing due to their excellent optical properties, and photoluminescence sensors made from them can monitor gas concentration. However, the toxicity and intrinsic instability of lead-based perovskites have limited their commercial development. Meanwhile, perovskites have rarely been studied in the mid-infrared range. Herein, Cs2AgIn1–xErxCl6-ZBLAN perovskite fluoride glasses with outstanding mid-infrared luminescence are successfully prepared. A CO2 monitor device is fabricated using a Cs2AgIn1–xErxCl6-ZBLAN perovskite fluoride glass. The dense and inert nature of the glass is used to isolate the lead-free perovskite Cs2AgInCl6 from the external environment, thereby improving stability. The luminescence intensity of the Cs2AgIn1–xErxCl6-ZBLAN perovskite fluoride glass can still be maintained at more than 90% of its original level after 35 h of continuous UV lamp irradiation at 365 nm. The substitution of Er3+ for In3+ to form Cs2AgIn1–xErxCl6-ZBLAN perovskite fluoride glasses makes them promising candidates for future mid-infrared-emitting materials.

The synthesis of cyclic carbonates, which utilizes CO2 as a feedstock, is among the transformations presenting an opportunity to reduce CO2 emissions, while enhancing independence from fossil fuels. Desirability lies in the development of efficient, economically viable and sustainable catalysts for this approach. Many recent publications describe the successful utilization of eutectic solvents/deep eutectic solvents for the synthesis of cyclic carbonates. Nevertheless, the majority of them focuses on reporting catalyst performance (product yield) and reaction conditions (temperature, pressure, reaction time) with little insights into the sustainability aspects (process mass intensity (PMI), solvents, and critical elements involved, as well as health and safety parameters described by H-code). Taking an example of the system composed of naturally occurring, inexpensive tannic acid combined with choline halides, the green chemistry metrics were evaluated for different DESs and other two-component catalysts and discussed in terms of guiding future designs of sustainable catalytic systems for the synthesis of cyclic carbonates.

Chitin, a highly insoluble and poorly degradable polymer derived from seafood industry waste, can be converted into value-added products including N-acetylchitobiose ((GlcNAc)2) and N-acetylglucosamine (GlcNAc) by chitinase, which can overcome the disadvantages of chemical degradation. Here, we identified a novel salt-tolerant chitinase (CHI) involved in chitin degradation from Bacillus clausii TCCC 11004. Recombinant CHI (rCHI) displayed a great tolerance against high concentrations of NaCl, maintaining 376% of its initial activity in a solution containing 0.6 M NaCl, which was about NaCl concentration in seawater. Chitin binding domain (ChBD) engineering demonstrated that rCHI’s ChBD was beneficial for its NaCl resistance property. As a multifunctional chitinase, rCHI exhibited dual exochitinase activity and N-acetylglucosaminidase activity, but no hydrolytic activity toward (GlcNAc)2 when using colloidal chitin as a substrate, which made it different from the typical reported chitinases. As a result, (GlcNAc)2 and GlcNAc achieved the maximum yield ((GlcNAc)2: 25.73 mg/mL and GlcNAc: 3.25 mg/mL) by hydrolyzing colloidal chitin from crab shells using rCHI alone. This study reported a valuable chitinase with the above dual activities and provided an eco-friendly and sustainable approach for cost-effective bioconversion of chitin-containing biowastes to bioactive (GlcNAc)2 and GlcNAc.

Electrochemical flow reactors are increasingly relevant platforms in emerging sustainable energy conversion and storage technologies. As a prominent example, redox flow batteries, a well-suited technology for large energy storage if the costs can be significantly reduced, leverage electrochemical reactors as power converting units. Within the reactor, the flow field geometry determines the electrolyte pumping power required, mass transport rates, and overall cell performance. However, current designs are inspired by fuel cell technologies but have not been engineered for redox flow battery applications, where liquid-phase electrochemistry is sustained. Here, we leverage stereolithography 3D printing to manufacture lung-inspired flow field geometries and compare their performance to conventional flow field designs. A versatile two-step process based on stereolithography 3D printing followed by a coating procedure to form a conductive structure is developed to manufacture lung-inspired flow field geometries. We employ a suite of fluid dynamics, electrochemical diagnostics, and finite element simulations to correlate the flow field geometry with performance in symmetric flow cells. The lung-inspired structural pattern is demonstrated to homogenize the reactant distribution in the porous electrode and to improve the electrolyte accessibility to the electrode reaction area. In addition, the results reveal that these novel flow field geometries can outperform conventional interdigitated flow field designs, as these patterns exhibit a more favorable electrical and pumping power balance, achieving superior current densities at lower pressure loss. Although at its nascent stage, additive manufacturing offers a versatile design space for manufacturing engineered flow field geometries for advanced flow reactors in emerging electrochemical energy storage technologies.

Nanostructured products are an actively growing area for food research, but there is little information on the sustainability of processes used to make these products. In this Review, we advocate for selection of sustainable process technologies during initial stages of laboratory-scale developments of nanofoods. We show that selection is assisted by predictive sustainability assessment(s) based on conventional technologies, including exploratory ex ante and “anticipatory” life-cycle assessment. We demonstrate that sustainability assessments for conventional food process technologies can be leveraged to design nanofood process concepts and technologies. We critically review emerging nanostructured food products including encapsulated bioactive molecules and processes used to structure these foods at laboratory, pilot, and industrial scales. We apply a rational method via learning lessons from sustainability of unit operations in conventional food processing and critically apportioned lessons between emerging and conventional approaches. We conclude that this method provides a quantitative means to incorporate sustainability during process design for nanostructured foods. Findings will be of interest and benefit to a range of food researchers, engineers, and manufacturers of process equipment.

Aluminum batteries with aluminum as the anode and organic materials as the cathode have continuously drawn considerable attention because of their high theoretical energy density, natural abundance, and environmentally benign nature. Herein, we have done an elaborate design work on the basis of π–π conjugated organic molecule PTCDA by a molecular engineering strategy. Introducing a sulfur atom to replace the H atom in the aromatic ring of the PTCDA molecule to form SPTCDA (sulfurized PTCDA) with p−π conjugated system can reduce the energy level of the molecule. In addition, the extension of the conjugated system makes the electrons more delocalized, which is beneficial to the improvement of the conductivity of SPTCDA. Experimental results show that compared with pristine PTCDA, SPTCDA has a more stable structure and better cycle performance, rate capability, and coulombic efficiency, as well as a higher discharge voltage plateau. To further understand the electronic structure, operating voltage, and correct redox mechanism, density functional theory (DFT) calculations were performed for PTCDA and SPTCDA. The diffusion behavior of ions on the electrode surface was also discussed. This work reveals an important molecular structure design strategy for a carbonyl cathode, in order to break the application limitations of this electrode material on aluminum organic batteries.

Designing sustainable epoxy resins with intrinsic recyclability and degradability has become vital in polymer science. Here, we report sulfur chain-modified epoxy networks (SxEyUz) through catalyst-free tri-component polymerization of elemental sulfur with glycidyl ethers of bio-sourced eugenol (EGE) and 10-undecenol (UGE) via inverse vulcanization. The biogenic allyl protons on EGE were disclosed to be critical for the dual-mechanism cross-linking system. Intermediates from the tri-component polymerization were found to be flowable, storable, and post-curable. Reprocessable epoxy polymers with tensile strength up to 13.0 MPa were obtained after curing, surpassing most reported bio-based polymers via inverse vulcanization. Carbon fiber (CF) composites fabricated in the SxEyUz matrix can be readily digested in a methanol solution of Na2S and neat hexylamine to recycle CF.

Electrocatalytically reducing gaseous CO2 to high value-added chemical fuels is an ideal method to address energy and environmental issues. To achieve high Faradic efficiency (FE) of specific products with high current density for the CO2 reduction reaction (CO2RR), it is crucial to design suitable electrocatalysts to understand the relationship of structure and performance. Herein, we synthesized a hydrophobic porous carbon scaffold loaded with Au nanoparticles to explore the effect of the porous structure on CO2RR performance. As high as 92% FE of CO is achieved over the optimized 20%Au/FPC-800 electrocatalyst within the applied potential range of −0.7 to −1.1 V versus RHE, and its current density toward CO2RR is also much larger than that of other three electrocatalysts for comparison. Based on the characterization of CO2 adsorption/desorption, Tafel slope, electrochemical impedance spectroscopy (EIS), and in situ attenuated total reflection-surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) analysis, it is proposed that the hydrophobic porous structure favors CO2 storage, which can enhance the mass transfer of low-soluble CO2 molecules to the electrocatalyst interface during CO2RR. Our findings provide a strategy for achieving high FE of converting CO2 to generate a CO product with a high current density.