Carbon Catalysts Empowering Sustainable Chemical Synthesis via Electrochemical CO2 Conversion and Two-Electron Oxygen Reduction Reaction.

Carbon materials hold significant promise in electrocatalysis, particularly in electrochemical CO2 reduction reaction (eCO2 RR) and two-electron oxygen reduction reaction (2e- ORR). The pivotal factor in achieving exceptional overall catalytic performance in carbon catalysts is the strategic design of specific active sites and nanostructures. This work presents a comprehensive overview of recent developments in carbon electrocatalysts for eCO2 RR and 2e- ORR. The creation of active sites through single/dual heteroatom doping, functional group decoration, topological defect, and micro-nano structuring, along with their synergistic effects, is thoroughly examined. Elaboration on the catalytic mechanisms and structure-activity relationships of these active sites is provided. In addition to directly serving as electrocatalysts, this review explores the role of carbon matrix as a support in finely adjusting the reactivity of single-atom molecular catalysts. Finally, the work addresses the challenges and prospects associated with designing and fabricating carbon electrocatalysts, providing valuable insights into the future trajectory of this dynamic field.

Precise Design and Modification Engineering of Single-Atom Catalytic Materials for Oxygen Reduction.

Due to their unique electronic and structural properties, single-atom catalytic materials (SACMs) hold great promise for the oxygen reduction reaction (ORR). Coordinating environmental and engineering strategies is the key to improving the ORR performance of SACMs. This review summarizes the latest research progress and breakthroughs of SACMs in the field of ORR catalysis. First, the research progress on the catalytic mechanism of SACMs acting on ORR is reviewed, including the latest research results on the origin of SACMs activity and the analysis of pre-adsorption mechanism. The study of the pre-adsorption mechanism is an important breakthrough direction to explore the origin of the high activity of SACMs and the practical and theoretical understanding of the catalytic process. Precise coordination environment modification, including in-plane, axial, and adjacent site modifications, can enhance the intrinsic catalytic activity of SACMs and promote the ORR process. Additionally, several engineering strategies are discussed, including multiple SACMs, high loading, and atomic site confinement. Multiple SACMs synergistically enhance catalytic activity and selectivity, while high loading can provide more active sites for catalytic reactions. Overall, this review provides important insights into the design of advanced catalysts for ORR.

Boosting 5-Hydroxymethylfurfural Electrooxidation by Porous Biochar via Loading Numerous Surface-Exposed Cobalt Phosphonates.

The electrooxidation of 5-hydroxymethylfurfural (HMF) into 2,5-furandicarboxylic acid (FDCA) demonstrated its unique superiority, not only in reducing overpotential and improving energy conversion efficiency for green hydrogen production but also in utilizing abundant biomass resources and producing high-value-added chemicals. However, designing highly efficient electrocatalysts for HMF electrooxidation (HMF-EOR) with low cost and high performance for large-scale production remained a huge challenge. Herein, we introduced an easy one-step activation process to produce P-doped porous biochar loaded with multiple crystal surfaces exposed to CoP2O6 catalysts (CoP2O6@PC), which exhibited outstanding electrooxidation performance. To achieve a current density of 50 mA cm-2, only a low overpotential of 200 mV was needed for the electrooxidation of HMF in 1.0 M KOH + 10 mM HMF. This performance far surpassed that of other similar materials. CoP2O6@PC exhibited outstanding HMF-EOR performance with high conversion (nearly 100%), selectivity (97.1%), faradaic efficiency (95.3%), and robust stability. This work represents a promising strategy to fabricate macroscale and low-cost HMF-EOR electrocatalysts and achieve potential industrial applications of HMF-EOR.

Fe, N-Inducing Interfacial Electron Redistribution in NiCo Spinel on Biomass-Derived Carbon for Bi-functional Oxygen Conversion.

Herein, an interfacial electron redistribution is proposed to boost the activity of carbon-supported spinel NiCo2O4 catalyst toward oxygen conversion via Fe, N-doping strategy. Fe-doping into octahedron induces a redistribution of electrons between Co and Ni atoms on NiCo1.8Fe0.2O4@N-carbon. The increased electron density of Co promotes the coordination of water to Co sites and further dissociation. The generation of proton from water improves the overall activity for the oxygen reduction reaction (ORR). The increased electron density of Ni facilitates the generation of oxygen vacancies. The Ni-VO-Fe structure accelerates the deprotonation of *OOH to improve the activity toward oxygen evolution reaction (OER). N-doping modulates the electron density of carbon to form active sites for the adsorption and protonation of oxygen species. Fir wood-derived carbon endows catalyst with an integral structure to enable outstanding electrocatalytic performance. The NiCo1.8Fe0.2O4@N-carbon express high half-wave potential up to 0.86 V in ORR and low overpotential of 270 mV at 10 mA cm-2 in OER. The zinc-air batteries (ZABs) assembled with the as-prepared catalyst achieve long-term cycle stability (over 2000 cycles) with peak power density (180 mWcm-2). Fe, N-doping strategy drives the catalysis of biomass-derived carbon-based catalysts to the highest level for the oxygen conversion in ZABs.

Polystyrene Waste Thermochemical Hydrogenation to Ethylbenzene by a N-Bridged Co, Ni Dual-Atom Catalyst.

Recycling waste plastics requires the degradation of plastics into small molecules. However, various products are widely distributed using traditional methods of depolymerizing polystyrene (PS) such as catalytic pyrolysis and hydrogenolysis. Here, we creatively report a N-bridged Co, Ni dual-atom (Co-N-Ni) catalyst for the targeted conversion of waste PS plastics to ethylbenzene via a pressurized tandem fixed-bed reactor where hydropyrolysis is coupled with downstream vapor-phase hydrotreatment. The Co-N-Ni catalyst achieves 95 wt % PS conversion with 92 wt % ethylbenzene yield, significantly superior to the corresponding single-atom catalysts, and enables degradation of real PS plastics. Theoretical calculations and experimental results demonstrate that the d-band center of metal atoms is well regulated in the Co-N-Ni catalyst. The Co site activates the C═C bond more easily, while the Ni site spatially optimizes the adsorption configuration of the styrene molecule due to the electronic interaction. This Co-N-Ni catalyst in the tandem reactor also shows excellent durability and provides a new direction for real plastic degradation.

Mixed Plastics Wastes Upcycling with High-Stability Single-Atom Ru Catalyst.

Mixed plastic waste treatment has long been a significant challenge due to complex composition and sorting costs. In this study, we have achieved a breakthrough in converting mixed plastic wastes into a single chemical product using our innovative single-atom catalysts for the first time. The single-atom Ru catalyst can convert ∼90% of real mixed plastic wastes into methane products (selectivity >99%). The unique electronic structure of Ru sites regulates the adsorption energy of mixed plastic intermediates, leading to rapid decomposition of mixed plastics and superior cycle stability compared to traditional nanocatalysts. The global warming potential of the entire process was evaluated. Our proposed carbon-reducing process utilizing single-atom catalysts launches a new era of mixed plastic waste valorization.

Heterogeneous Catalysis in Production and Utilization of Formic Acid for Renewable Energy.

As the cleanest energy source, hydrogen has been followed with interest by researchers around the world. However, due to the internal low density of hydrogen, it cannot be stored and used efficiently which limits the hydrogen application on a huge scale. Chemical hydrogen storage is considered as a useful method for efficient handling and storage. Due to its excellent safety, formic acid stands out. It is worth noting that the matter and energy conversion is established based on formic acid, which is not referred to in the previous documentation. In this review, the latest development of research on heterogeneous catalysis via production and application of formic acid for energy application is reported. The matter and energy conversion based on formic acid are both discussed systematically. More importantly, with formic acid as the node, biomass energy shows potential to be in a dominant position in the energy conversion process. In addition, the catalytic mechanism is also mentioned. This review can provide the current state in this field and the new inspirations for developing superior catalytic systems.

Co-Adjusting d-Band Center of Fe to Accelerate Proton Coupling for Efficient Oxygen Electrocatalysis.

The problem in d-band center modulation of transition metal-based catalysts for the rate-determining steps of oxygen conversion is an obstacle to boost the electrocatalytic activity by accelerating proton coupling. Herein, the Co doping to FeP is adopted to modify the d-band center of Fe. Optimized Fe sites accelerate the proton coupling of oxygen reduction reaction (ORR) on N-doped wood-derived carbon through promoting water dissociation. In situ generated Fe sites optimize the adsorption of oxygen-related intermediates of oxygen evolution reaction (OER) on CoFeP NPs. Superior catalytic activity toward ORR (half-wave potential of 0.88 V) and OER (overpotential of 300 mV at 10 mA cm-2 ) express an unprecedented level in carbon-based transition metal-phosphide catalysts. The liquid zinc-air battery presents an outstanding cycling stability of 800 h (2400 cycles). This research offers a newfangled perception on designing highly efficient carbon-based bifunctional catalysts for ORR and OER.

Wood-Derived Monolithic Catalysts with the Ability of Activating Water Molecules for Oxygen Electrocatalysis.

Oxygen reduction reaction (ORR) is the key reaction on cathode of rechargeable zinc-air batteries (ZABs). However, the lack of protons in alkaline conditions limits the rate of ORR. Herein, an activating water strategy is proposed to promote oxygen electrocatalytic activity by enhancing the proton production from water dissociation. FeP nanoparticles (NPs) are coupled on N-doped wood-derived catalytically active carbon (FeP-NWCC) to associate bifunctional active sites. In alkaline, FeP-NWCC possesses outstanding catalytic activities toward ORR (E1/2  = 0.86 V) and Oxygen evolution reaction (OER) (overpotential is 310 mV at 10 mA cm-2 ). The liquid ZABs assembled by FeP-NWCC deliver superior peak power density (144 mW cm-2 ) and cycle stability (over 450 h). The quasi-solid-state ZABs based on FeP-NWCC also display excellent performances. Theoretical calculation illustrates that the superb bifunctional performance of FeP-NWCC results from the elevated dissociation efficiency of water via FeP NPs to assist the oxygen catalytic process. The strategy of activating water provides a new perspective for the design of ORR/OER bifunctional catalysts. This work is a model for the application of forest biomass.

Coupling Fe3 C Nanoparticles and N-Doping on Wood-Derived Carbon to Construct Reversible Cathode for Zn-Air Batteries.

Electrochemical reduction of oxygen plays a critical role in emerging electrochemical energy technologies. Multiple electron transfer processes, involving adsorption and activation of O2 and generation of protons from water molecules, cause the sluggish kinetics of the oxygen reduction reaction (ORR). Herein, a double-active-site catalyst of Fe3 C nanoparticles coupled to paulownia wood-derived N-doped carbon (Fe3 C@NPW) is fabricated via an active-site-uniting strategy. One site on Fe3 C nanoparticles contributes to activating water molecules, while another site on N-doped carbon is responsible for activating oxygen molecules. Benefiting from the synergistic effect of double active sites, Fe3 C@NPW delivers a remarkable catalytic activity for ORR with a half-wave potential of 0.87 V (vs. RHE) in alkaline electrolyte, outperforming commercial Pt/C catalyst. Moreover, zinc-air batteries (ZABs) assembled with Fe3 C@NPW as a catalyst on cathode achieve a large specific capacity of 804.4 mA h gZn-1 and a long-term stability of 780 cycles. The model solid-state ZABs also display satisfactory performances with an open-circuit voltage of 1.39 V and a high peak power density of 78 mW cm-2 . These outstanding performances reach the level of first-rank among the non-noble metal electrode materials. This work offers a promising approach to creating double-active-site catalysts by the active-site-uniting strategy for energy conversion fields.

CO2 Laser-Induced Graphene with an Appropriate Oxygen Species as an Efficient Electrocatalyst for Hydrogen Peroxide Synthesis.

Oxygen species functionalized graphene (O-G) is an effective electrocatalyst for electrochemically synthesizing hydrogen peroxide (H2 O2 ) by a 2 e- oxygen reduction reaction (ORR). The type of oxygen species and degree of carbon crystallinity in O-G are two key factors for the high catalytic performance of the 2 e- ORR. However, the general preparing method of O-G by the precursor of graphite has the disadvantages of consuming massive strong oxidant and washing water. Herein, the biomass-based graphene with tunable oxygen species is rapidly fabricated by a CO2 laser. In a flow cell setup, the laser-induced graphene (LIG) with abundant active oxygen species and graphene structure shows high catalytic performance including high Faraday efficiency (over 78 %) and high mass activity (814 mmolgcatalyst -1  h-1 ), superior to most of the reported carbon-based electrocatalysts. Density function theory demonstrates the meta-C atoms at nearby C-O, O-C=O species are the key catalytic sites. Therefore, we develop one facile method to rapidly convert biomass to graphene electrocatalyst used for H2 O2 synthesis.

Isolation of Bacillus sp. with high laccase activity for green biodecolorization of synthetic textile dyes.

New Bacillus sp. strains with spore-laccase activity were isolated from rotten wood and soil samples and were identified as Bacillus sp. FM-78 and Bacillus paramycoides FM-86 by 16S rDNA gene sequence analysis. Both laccases were stable at broad pH range and high temperature. The laccase of strain FM-78 showed preferable activity and stability, with no loss of activity after 7 days incubation at pH 9.0, and 20.36% of its initial activity obtained after 10 h at 80 °C. 1 mmol/L EDTA, NaN3 and SDS resulted in about 46-59% inactivation and strongly inhibition (87.88%) was caused by 1 mmol/L L-cysteine. However, the spore laccase could tolerate towards 0.5 mol/L NaCl as well as 10% of organic solvents. Reactive black 5, reactive blue 19 and crystal violet were decolorized by the spore laccase in the absence of mediator. The decolorization process was efficiently promoted with the presence of acetosyringone, and the color removal ratio was more than 80% in 1 h with the pH values of 6.6 or 9.0. Finally, the above unusual properties of Bacillus sp. spore laccase indicated it as a potential candidate in the dye decolorization in an ecofriendly and cost-effective way.

Wood-Derived Integral Air Electrode for Enhanced Interfacial Electrocatalysis in Rechargeable Zinc-Air Battery.

Zinc-air batteries (ZABs) are promising as energy storage devices owing to their high energy density and the safety of electrolytes. Construction of abundant triple-phase boundary (TPB) effectively facilitates cathode reactions occurring at TPB. Herein, a wood-derived integral air electrode containing Co/CoO nanoparticles and nitrogen-doped carbonized wood (Co/CoO@NWC) is constructed with a dual catalytic function. The potential gap between oxygen reduction and evolution is shortened to 0.77 V. Liquid ZABs using Co/CoO@NWC as cathode exhibit high discharge specific capacity (800 mAh gZn-1 ), low charge-discharge gap (0.84 V), and long-term cycling stability (270 h). Co/CoO@NWC also shows distinguished catalytic activity and stability in all-solid-state ZABs. The inherent layered porous and pipe structures of wood are well maintained in catalytically active carbon. The different hydrophilicity of carbonized wood and Co/CoO endow abundant TPBs for battery reaction. The Co/CoO located on TPB provides main active sites for oxygen reactions. The inherent pipe structures of wood carbon and the interaction between Co/CoO and NWC effectively prevent nanoparticles from aggregation. The design and preparation of this monolithic electrocatalyst contribute to the broad-scale application of ZABs and promote the development of next-generation biomass-based storage devices.

Advances and Prospects in Metal-Organic Frameworks as Key Nexus for Chemocatalytic Hydrogen Production.

Hydrogen is a clean and sustainable energy carrier, which is considered a promising alternative for fossil fuels to solve the global energy crisis and respond to climate change. Social concerns on its safe storage promote continuous exploration of alternatives to traditional storage methods. In this case, chemical hydrogen storage materials initiate plentiful research with special attention to the design of heterogeneous catalysts that can enhance efficient and highly selective hydrogen production. Metal-organic frameworks (MOFs), a kind of unique crystalline porous materials featuring highly ordered porosities and tailorable structures, can provide various active sites (i.e., metal nodes, functional linkers, and defects) for heterogeneous catalysis. Furthermore, the easy construction of active sites in highly ordered MOFs, which can work as plate for the delicate active site engineering, make them ideal candidates for a variety of heterogeneous catalysts including chemocatalytic hydrogen production. This review concentrates on the application of MOFs as heterogeneous catalysts or catalyst supports in chemocatalytic hydrogen production. Recent progresses of MOFs as catalysts for chemocatalytic hydrogen production are comprehensively summarized. The research methods, mechanism analyses, and prospects of MOFs in this field are discussed. The challenges in future industrial applications of MOFs as catalysts for hydrogen production are proposed.

Design, Synthesis, and Biological Evaluation of Novel 6H-Benzo[c]chromen-6-one Derivatives as Potential Phosphodiesterase II Inhibitors.

Urolithins (hydroxylated 6H-benzo[c]chromen-6-ones) are the main bioavailable metabolites of ellagic acid (EA), which was shown to be a cognitive enhancer in the treatment of neurodegenerative diseases. As part of this research, a series of alkoxylated 6H-benzo[c]chromen-6-one derivatives were designed and synthesized. Furthermore, their biological activities were evaluated as potential PDE2 inhibitors, and the alkoxylated 6H-benzo[c]chromen-6-one derivative 1f was found to have the optimal inhibitory potential (IC50: 3.67 ± 0.47 µM). It also exhibited comparable activity in comparison to that of BAY 60-7550 in vitro cell level studies.

Promoting Aromatic Hydrocarbon Formation via Catalytic Pyrolysis of Polycarbonate Wastes over Fe- and Ce-Loaded Aluminum Oxide Catalysts.

Converting polycarbonate (PC) plastic waste into value-added chemicals and/or fuel additives by catalytic pyrolysis is a promising approach to dispose of solid wastes. In this study, a series of Fe-Ce@Al2O3 metal oxides were prepared by coprecipitation, impregnation, and a direct mixing method. The synthesized catalysts were then employed to investigate the catalytic conversion of PC wastes to produce aromatic hydrocarbons. Experimental results indicated that Fe-Ce@Al2O3 prepared by coprecipitation possessed superior catalytic activity because of its high content of weak acid sites, large pore volume, high surface area, and well dispersion of Fe and Ce active species, leading to an ∼3-fold increase in targeted monocyclic aromatic hydrocarbons compared to that achieved noncatalytically. Moreover, an increase in the catalyst to feedstock (C/F) mass ratio was beneficial to the production of aromatic hydrocarbons at the expense of phenolic products, and elevating the C/F ratio from 1:1 to 3:1 considerably increased the benzene formation as the enhancement factor was increased from 2.3 to 8.8.

Characterization of a novel thermostable glucose-tolerant GH1 ß-glucosidase from the hyperthermophile Ignisphaera aggregans and its application in the efficient production of baohuoside I from icariin and total epimedium flavonoids.

The minor flavonoid baohuoside I from Herba epimedii has better bioactivities than its precursor compounds icariin and other major epimedium flavonoids. In this study, a novel ß-glucosidase gene (Igag_0940) was cloned and expressed to improve the conversion efficiency in the process of baohuoside I production. For the first time, the recombinant IagBgl1 was purified and then identified uniquely as a trimer in GH 1 family protein from Archaea. The maximum activity of recombinant IagBgl1 was exhibited at 95 °C, pH 6.5, and it retained more than 70% after incubation at 90 °C for 4 h. IagBgl1 had a high catalytic activity towards icariin with a Kcat/Km ratio of 488.19 mM-1·s-1. Under optimized conditions (65 °C, pH 6.5, 0.8 U/mL enzyme, and 90 min), 10 g/L icariin was transformed into 7.564 g/L baohuoside I with a molar conversion of 99.48%. Meanwhile, 2.434 g/L baohuoside I was obtained from 10 g/L total epimedium flavonoids by a two-step conversion system built with IagBgl1 and two other thermostable enzymes. This is the first report of enzymatic conversion for producing baohuoside I by thermostable enzymes.

Photocatalytic Cleavage of ß-O-4 Ether Bonds in Lignin over Ni/TiO2.

It is of great importance to explore the selective hydrogenolysis of ß-O-4 linkages, which account for 45-60% of all linkages in native lignin, to produce valued-added chemicals and fuels from biomass employing UV light as catalyst. TiO2 exhibited satisfactory catalytic performances in various photochemical reactions, due to its versatile advantages involving high catalytic activity, low cost and non-toxicity. In this work, 20 wt.% Ni/TiO2 and oxidant PCC (Pyridinium chlorochromate) were employed to promote the cleavage of ß-O-4 alcohol to obtain high value chemicals under UV irradiation at room temperature. The Ni/TiO2 photocatalyst can be magnetically recovered and efficiently reused in the following four consecutive recycling tests in the cleavage of ß-O-4 ether bond in lignin. Mechanism studies suggested that the oxidation of ß-O-4 alcohol to ß-O-4 ketone by oxidant PCC first occurred during the reaction, and was followed by the photocatalysis of the obtained ß-O-4 ketone to corresponding acetophenone and phenol derivates. Furthermore, the system was tested on a variety of lignin model substrates containing ß-O-4 linkage for the generation of fragmentation products in good to excellent results.

Positively charged phthalocyanine-arginine conjugates as efficient photosensitizer for photodynamic therapy.

Positively charged drugs usually have enhanced water solubility, cellular uptake efficiency and anticancer activity. However, the common quaternized and protonated cationic photosensitizers both have some drawbacks such as needing potentially dangerous agents for preparation and easily being deprotonated in alkaline circumstance. Arginine is unique among the amino acids as its guanidine group has exceptionally high basicity in aqueous solution, which may make it positively charged in a wide range of pH. In this paper, two arginine substituted zinc phthalocyanines (ArgEZnPc and ArgZnPc) were reported. They can be positively charged in the range of pH 5-9. Moreover, the photobiological, photochemical properties, subcellular localization, and in vitro anticancer activities of the them were also carried out. The results show that ArgZnPc may be not a good photosensitizer because of its poor photobiological activities though it is positively charged in a wide range of pHs. This may be attributed to the formation of inner salts between guanidine and carboxyl groups of ArgZnPc, which weakens its photobiological and in vitro anticancer activity. While in contrast, ArgEZnPc shows preferential localization in the lysosomes of HeLa cells, exhibits high water solubility, excellent 1O2 and intracellular reactive oxygen species generation efficiency as well as high in vitro anticancer activity, making it a promising photosensitizer for photodynamic therapy.

Converting waste tires into p-cymene through hydropyrolysis and selective gas-phase hydrogenation/dehydrogenation.

The resource utilization and valorization of waste tires (WT) are of significant importance in reducing environmental pollution. To produce high-value p-cymene from WT, we propose a catalytic cascade process combining hydropyrolysis and catalytic gas-phase hydrotreating in a two-stage fixed-bed reactor. The effect of catalysts prepared with three different acidic supports on the hydrogenation/dehydrogenation of limonene, a compound derived from the hydropyrolysis of WT, was investigated. The p-cymene formation could be controlled by optimizing process parameters, including hydropyrolysis temperature, hydrogenation temperature, and catalyst-to-feedstock ratio (C/F). Experimental results indicated that, in the absence of a catalyst, limonene was the main product of WT depolymerization. Under optimized conditions (hydropyrolysis temperature of 425 ℃, hydrotreating temperature of 400 ℃, C/F of 10:1, and reaction pressure of 0.15 MPa), the highest relative content of p-cymene (79.1%) was obtained over the Pd/SBA-15 catalyst. This demonstrates that our proposed catalytic cascade process of hydropyrolysis and selective gas-phase hydrogenation/dehydrogenation can convert WT into p-cymene with high added value.