Photothermal CO2 conversion to ethanol through photothermal heterojunction-nanosheet arrays.

Photothermal CO2 conversion to ethanol offers a sustainable solution for achieving net-zero carbon management. However, serious carrier recombination and high C-C coupling energy barrier cause poor performance in ethanol generation. Here, we report a Cu/Cu2Se-Cu2O heterojunction-nanosheet array, showcasing a good ethanol yield under visible-near-infrared light without external heating. The Z-scheme Cu2Se-Cu2O heterostructure provides spatially separated sites for CO2 reduction and water oxidation with boosted carrier transport efficiency. The microreactors induced by Cu2Se nanosheets improve the local concentration of intermediates (CH3* and CO*), thereby promoting C-C coupling process. Photothermal effect of Cu2Se nanosheets elevates system's temperature to around 200 °C. Through synergizing electron and heat flows, we achieve an ethanol generation rate of 149.45 µmol g-1 h-1, with an electron selectivity of 48.75% and an apparent quantum yield of 0.286%. Our work can serve as inspiration for developing photothermal catalysts for CO2 conversion into multi-carbon chemicals using solar energy.

High-Rate and Selective C2H6-to-C2H4 Photodehydrogenation Enabled by Partially Oxidized Pdδ+ Species Anchored on ZnO Nanosheets under Mild Conditions.

Photocatalytic C2H6-to-C2H4 conversion is very promising, yet it remains a long-lasting challenge due to the high C-H bond dissociation energy of 420 kJ mol-1. Herein, partially oxidized Pdδ+ species anchored on ZnO nanosheets are designed to weaken the C-H bond by the electron interaction between Pdδ+ species and H atoms, with efforts to achieve high-rate and selective C2H6-to-C2H4 conversion. X-ray photoelectron spectra, Bader charge calculations, and electronic localization function demonstrate the presence of partially oxidized Pdδ+ sites, while quasi-in situ X-ray photoelectron spectra disclose the Pdδ+ sites initially adopt and then donate the photoexcited electrons for C2H6 dehydrogenation. In situ electron paramagnetic resonance spectra, in situ Fourier transform infrared spectra, and trapping agent experiments verify C2H6 initially converts to CH3CH2OH via ·OH radicals, then dehydroxylates to CH3CH2· and finally to C2H4, accompanied by H2 production. Density-functional theory calculations elucidate that loading Pd site can lengthen the C-H bond of C2H6 from 1.10 to 1.12 Å, which favors the C-H bond breakage, affirmed by a lowered energy barrier of 0.04 eV. As a result, the optimized 5.87% Pd-ZnO nanosheets achieve a high C2H4 yield of 16.32 mmol g-1 with a 94.83% selectivity as well as a H2 yield of 14.49 mmol g-1 from C2H6 dehydrogenation in 4 h, outperforming all the previously reported photocatalysts under similar conditions.

Breaking the Activity-Selectivity Trade-off for CH4-to-C2H6 Photoconversion.

Photocatalytic conversion of methane (CH4) to ethane (C2H6) has attracted extensive attention from academia and industry. Typically, the traditional oxidative coupling of CH4 (OCM) reaches a high C2H6 productivity, yet the inevitable overoxidation limits the target product selectivity. Although the traditional nonoxidative coupling of CH4 (NOCM) can improve the product selectivity, it still encounters unsatisfied activity, arising from being thermodynamically unfavorable. To break the activity-selectivity trade-off, we propose a conceptually new mechanism of H2O2-triggered CH4 coupling, where the H2O2-derived ·OH radicals are rapidly consumed for activating CH4 into ·CH3 radicals exothermically, which bypasses the endothermic steps of the direct CH4 activation by photoholes and the interaction between ·CH3 and ·OH radicals, affirmed by in situ characterization techniques, femtosecond transient absorption spectroscopy, and density-functional theory calculation. By this pathway, the designed Au-WO3 nanosheets achieve unprecedented C2H6 productivity of 76.3 mol molAu-1 h-1 with 95.2% selectivity, and TON of 1542.7 (TOF = 77.1 h-1) in a self-designed flow reactor, outperforming previously reported photocatalysts regardless of OCM and NOCM pathways. Also, under outdoor natural sunlight irradiation, the Au-WO3 nanosheets exhibit similar activity and selectivity toward C2H6 production, showing the possibility for practical applications. Interestingly, this strategy can be applied to other various photocatalysts (Au-WO3, Au-TiO2, Au-CeO2, Pd-WO3, and Ag-WO3), showing a certain universality. It is expected that the proposed mechanism adds another layer to our understanding of CH4-to-C2H6 conversion.

A non-metal single atom nanozyme for cutting off the energy and reducing power of tumors.

Enzymes are considered safe and effective therapeutic tools for various diseases. With the increasing integration of biomedicine and nanotechnology, artificial nanozymes offer advanced controllability and functionality in medical design. However, several notable gaps, such as catalytic diversity, specificity and biosafety, still exist between nanozymes and their native counterparts. Here we report a non-metal single-selenium (Se)-atom nanozyme (SeSAE), which exhibits potent nicotinamide adenine dinucleotide phosphate (NADPH) oxidase-mimetic activity. This novel single atom nanozyme provides a safe alternative to conventional metal-based catalysts and effectively cuts off the cellular energy and reduction equivalents through its distinctive catalytic function in tumors. In this study, we have demonstrated the substantial efficacy of SeSAE as an antitumor nanomedicine across diverse mouse models without discernible systemic adverse effects. The mechanism of the NADPH oxidase-like activity of the non-metal SeSAE was rationalized by density functional theory calculations. Furthermore, comprehensive elucidation of the biological functions, cell death pathways, and metabolic remodeling effects of the nanozyme was conducted, aiming to provide valuable insights into the development of single atom nanozymes with clinical translation potential.

Dynamically Reconstructed Triple-Copper-Vacancy Associates Confined in Cu Nanowires Enabling High-Rate and Selective CO2 Electroreduction to C2+ Products.

Electrochemically reconstructed Cu-based catalysts always exhibit enhanced CO2 electroreduction performance; however, it still remains ambiguous whether the reconstructed Cu vacancies have a substantial impact on CO2-to-C2+ reactivity. Herein, Cu vacancies are first constructed through electrochemical reduction of Cu-based nanowires, in which high-angle annular dark-field scanning transmission electron microscopy image manifests the formation of triple-copper-vacancy associates with different concentrations, confirmed by positron annihilation lifetime spectroscopy. In situ attenuated total reflection-surface enhanced infrared absorption spectroscopy discloses the triple-copper-vacancy associates favor *CO adsorption and fast *CO dimerization. Moreover, density-functional-theory calculations unravel the triple-copper-vacancy associates endow the nearby Cu sites with enriched and disparate local charge density, which enhances the *CO adsorption and reduces the CO-CO coupling barrier, affirmed by the decreased *CO dimerization energy barrier by 0.4 eV. As a result, the triple-copper-vacancy associates confined in Cu nanowires achieve a high Faradaic efficiency of over 80% for C2+ products in a wide current density range of 400-800 mA cm-2, outperforming most reported Cu-based electrocatalysts.

Tandem Dual-Site PbCu Electrocatalyst for High-Rate and Selective Glycine Synthesis at Industrial Current Densities.

Direct electrosynthesis of high-value amino acids from carbon and nitrogen monomers remains a challenge. Here, we design a tandem dual-site PbCu electrocatalyst for efficient amino acid electrosynthesis. Using oxalic acid (H2C2O4) and hydroxylamine (NH2OH) as the raw reactants, for the first time, we have realized the flow-electrosynthesis of glycine at the industrial current density of 200 mA cm-2 with Faradaic efficiency over 78%. In situ ATR-FTIR spectroscopy characterizations reveal a favorable tandem pathway on the dual-site catalyst. Specifically, the Pb site drives the highly selective electroreduction of H2C2O4 to form glyoxylic acid, and the Cu site accelerates the fast hydrogenation of oxime to form a glycine product. A glycine electrosynthesis (GES)-formaldehyde electrooxidation (FOR) assembly is further established, which synthesizes more valuable chemicals (HCOOH, H2) while minimizing energy consumption. Altogether, we introduce a new strategy to enable the one-step electrosynthesis of high-value amino acid from widely accessible monomers.

Selective CO2 Photoreduction Enabled by Water-stable Cu-based Metal-organic Framework Nanoribbons.

The goal of photocatalytic CO2 reduction system is to achieve near 100 % selectivity for the desirable product with reasonably high yield and stability. Here, two-dimensional metal-organic frameworks are constructed with abundant and uniform monometallic active sites, aiming to be an emerged platform for efficient and selective CO2 reduction. As an example, water-stable Cu-based metal-organic framework nanoribbons with coordinatively unsaturated single CuII sites are first fabricated, evidenced by X-ray diffraction patterns and X-ray absorption spectroscopy. In situ Fourier-transform infrared spectra and Gibbs free energy calculations unravel the formation of the key intermediate COOH* and CO* is an exothermic and spontaneous process, whereas the competitive hydrogen evolution reaction is endothermic and non-spontaneous, which accounts for the selective CO2 reduction. As a result, in an aqueous solution containing 1 mol L-1 KHCO3 and without any sacrifice reagent, the water-stable Cu-based metal-organic framework nanoribbons exhibited an average CO yield of 82 µmol g-1 h-1 with the selectivity up to 97 % during 72 h cycling test, which is comparable to other reported photocatalysts under similar conditions.

Selective CO2 -to-C2 H4 Photoconversion Enabled by Oxygen-Mediated Triatomic Sites in Partially Oxidized Bimetallic Sulfide.

Selective CO2 photoreduction into C2 fuels under mild conditions suffers from low product yield and poor selectivity owing to the kinetic challenge of C-C coupling. Here, triatomic sites are introduced into bimetallic sulfide to promote C-C coupling for selectively forming C2 products. As an example, FeCoS2 atomic layers with different oxidation degrees are first synthesized, demonstrated by X-ray photoelectron spectroscopy and X-ray absorption near edge spectroscopy spectra. Both experiment and theoretical calculation verify more charges aggregate around the introduced oxygen atom, which enables the original Co-Fe dual sites to turn into Co-O-Fe triatomic sites, thus promoting C-C coupling of double *COOH intermediates. Accordingly, the mildly oxidized FeCoS2 atomic layers exhibit C2 H4 formation rate of 20.1 µmol g-1 h-1 , with the product selectivity and electron selectivity of 82.9 % and 96.7 %, outperforming most previously reported photocatalysts under similar conditions.

Boosting Ferroptosis Therapy with Iridium Single-Atom Nanocatalyst in Ultralow Metal Content.

Nanocatalysts are promising tumor therapeutics due to their ability to induce reactive oxygen species in the tumor microenvironment. Although increasing metal loading can improve catalytic activity, the quandary of high metal content versus potential systemic biotoxicity remains challenging. Here, a fully exposed active site strategy by site-specific anchoring of single iridium (Ir) atoms on the outer surface of a nitrogen-doped carbon composite (Ir single-atom catalyst (SAC)) is reported to achieve remarkable catalytic performance at ultralow metal content (≈0.11%). The Ir SAC exhibits prominent dual enzymatic activities to mimic peroxidase and glutathione peroxidase, which catalyzes the conversion of endogenous H2 O2 into •OH in the acidic TME and depletes glutathione (GSH) simultaneously. With an advanced support of GSH-trapping platinum(IV) and encapsulation with a red-blood-cell membrane, this nanocatalytic agent (Pt@IrSAC/RBC) causes intense lipid peroxidation that boosts tumor cell ferroptosis. The Pt@IrSAC/RBC demonstrates superior therapeutic efficacy in a mouse triple-negative mammary carcinoma model, resulting in complete tumor ablation in a single treatment session with negligible side effects. These outcomes may provide valuable insights into the design of nanocatalysts with high performance and biosafety for biomedical applications.

Micro-alkaline environment enables CO2 electroreduction to multicarbons.

Improving the efficiency towards multicarbons of electrocatalytic CO2 reduction is desirable but challenging. In this perspective, researchers reported the design of micro-alkaline environment could benefit this issue.

Progress and perspective for conversion of plastic wastes into valuable chemicals.

Today, discarded plastics in nature have caused serious "white pollution", however these plastic wastes contain abundant carbon resources that could serve as the feedstock to produce commodities. Because of this, it is requisite to convert these plastic wastes into valuable chemicals. Herein, the state-of-the-art techniques for plastic conversion are divided into two categories, those performed under violent conditions and mild conditions, in which the conversion mechanisms are discussed. The strategies under violent conditions are closer to practical application thanks to their excellent conversion efficiencies, while the strategies under mild conditions are more environmentally friendly, showing enormous development potential in the future. We summarize in detail the pyrolysis, hydropyrolysis, solvolysis and microwave-initiated catalysis for bond cleavage in plastic wastes at temperatures ranging from 448 to 973 K. Also, we overview the photocatalysis, electrocatalysis and biocatalysis for bond cleavage in plastic wastes at near and even normal temperature and pressure. Finally, we present some suggestions and outlooks concerning the improvement of current techniques and in-depth mechanisms of investigation for conversion of plastics into valuable chemicals.

Reversible Switching CuII /CuI Single Sites Catalyze High-rate and Selective CO2 Photoreduction.

Herein, we first design a model of reversible redox-switching metal-organic framework single-unit-cell sheets, where the abundant metal single sites benefit for highly selective CO2 reduction, while the reversible redox-switching metal sites can effectively activate CO2 molecules. Taking the synthetic Cu-MOF single-unit-cell sheets as an example, synchrotron-radiation quasi in situ X-ray photoelectron spectra unravel the reversible switching CuII /CuI single sites initially accept photoexcited electrons and then donate them to CO2 molecules, which favors the rate-liming activation into CO2 δ- , verified by in situ FTIR spectra and Gibbs free energy calculations. As an outcome, Cu-MOF single-unit-cell sheets achieve near 100 % selectivity for CO2 photoreduction to CO with a high rate of 860 µmol g-1 h-1 without any sacrifice reagent or photosensitizer, where both the activity and selectivity outperform previously reported photocatalysts evaluated under similar conditions.

Direct Polyethylene Photoreforming into Exclusive Liquid Fuel over Charge-Asymmetrical Dual Sites under Mild Conditions.

Direct polyethylene photoreforming to high-energy-density C2 fuels under mild conditions is of great significance and still faces a huge challenge, which is partly attributed to the extreme instability of *CH2CH2 adsorbed on the traditional catalysts with single catalytic sites. Herein, charge-asymmetrical dual sites are designed to boost the adsorption of *CH2CH2 for direct polyethylene photoreforming into C2 fuels under normal temperature and pressure. As a prototype, the synthetic Zr-doped CoFe2O4 quantum dots with charge-asymmetrical dual metal sites realize direct polyethylene photoreforming into acetic acid, with 100% selectivity of liquid fuel and the evolution rate of 1.10 mmol g-1 h-1, outperforming those of most previously reported photocatalysts under similar conditions. In situ X-ray photoelectron spectra, density-functional-theory calculations, and control experiments reveal the charge-asymmetrical Zr-Fe dual sites may act as the predominate catalytic sites, which can simultaneously bond with the *CH2CH2 intermediates for the following stepwise oxidation to form C2 products.

Plastics-to-syngas photocatalysed by Co-Ga2O3 nanosheets.

Plastics take hundreds of years to degrade naturally, while their chemical degradation typically requires high temperature and pressure. Here, we first utilize solar energy to realize the sustainable and efficient plastic-to-syngas conversion with the aid of water at ambient conditions. As an example, the commercial plastic bags could be efficiently photoconverted into renewable syngas by Co-Ga2O3 nanosheets, with hydrogen and carbon monoxide formation rates of 647.8 and 158.3 µmol g-1 h-1. In situ characterizations and labelling experiments unveil water is photoreduced into hydrogen, while non-recyclable plastics including polyethylene bags, polypropylene boxes and polyethylene terephthalate bottles are photodegraded into carbon dioxide, which is further selectively photoreduced into carbon monoxide. In-depth investigation illustrates that the efficiency of syngas production mainly depends on the carbon dioxide reduction process and hence photocatalysts of high carbon dioxide reduction activity should be designed to promote the efficiency of plastic-to-syngas conversion in the future. The concept for the photoreforming of non-recyclable plastics into renewable syngas helps to eradicate 'white pollution' and alleviate the energy crisis simultaneously.

Ultrathin Ti-doped WO3 nanosheets realizing selective photoreduction of CO2 to CH3OH.

Arduous CO2 activation and sluggish charge transfer retard the photoreduction of CO2 to CH3OH with high efficiency and selectivity. Here, we fabricate ultrathin Ti-doped WO3 nanosheets possessing approving active sites and optimized carrier dynamics as a promising catalyst. Quasi in situ X-ray photoelectron spectroscopy and synchrotron-radiation X-ray absorption near-edge spectroscopy firmly confirm that the true active sites for CO2 reduction are the W sites rather the Ti sites, while the Ti dopants can facilitate charge transfer, which accelerates the generation of crucial COOH* intermediates as revealed by in situ Fourier-transform infrared spectroscopy and density functional theory calculations. Besides, the Gibbs free energy calculations also validate that Ti doping can lower the energy barrier of CO2 activation and CH3OH desorption by 0.22 eV and 0.42 eV, respectively, thus promoting the formation of CH3OH. In consequence, the Ti-doped WO3 ultrathin nanosheets show a superior CH3OH selectivity of 88.9% and reach a CH3OH evolution rate of 16.8 µmol g-1 h-1, about 3.3 times higher than that on WO3 nanosheets. This work sheds light on promoting CO2 photoreduction to CH3OH by rational elemental doping.

Room-Temperature Photooxidation of CH4 to CH3OH with Nearly 100% Selectivity over Hetero-ZnO/Fe2O3 Porous Nanosheets.

The huge challenge for CH4 photooxidation into CH3OH lies in the activation of the inert C-H bond and the inhibition of CH3OH overoxidation. Herein, we design two-dimensional in-plane Z-scheme heterostructures composed of two different metal oxides, with efforts to polarize the symmetrical CH4 molecules and strengthen the O-H bond in CH3OH. As a prototype, we first fabricate ZnO/Fe2O3 porous nanosheets, where high-resolution transmission electron microscopy and in situ X-ray photoelectron spectroscopy affirm their in-plane Z-scheme heterostructure. In situ Fourier transform infrared spectra and in situ electron paramagnetic resonance spectra demonstrate their higher amount of ·CH3 radicals relative to the pristine ZnO porous nanosheets, in which density functional theory calculations validate that the high local charge accumulation on Fe sites lowers the CH4 adsorption energy from 0.14 to 0.06 eV. Moreover, the charge-accumulated Fe sites strengthen the polarity of the O-H bond in CH3OH through transferring electrons to the O atoms, confirmed by the increased barrier from 0.30 to 2.63 eV for *CH3O formation, which inhibits the homolytic O-H bond cleavage and thus suppresses CH3OH overoxidation. Accordingly, the CH3OH selectivity over ZnO/Fe2O3 porous nanosheets reaches up to nearly 100% with an activity of 178.3 µmol-1 gcat-1, outperforming previously reported photocatalysts without adding any oxidants under room temperature and ambient pressure.

Selective CO2 Photoreduction to CH4 via Pdδ+ -Assisted Hydrodeoxygenation over CeO2 Nanosheets.

Here, noble-metal-doped two-dimensional metal oxide nanosheets are designed to realize selective CO2 photoreduction to CH4 . As a prototype, Pd-doped CeO2 nanosheets are fabricated, where the active sites of Pdδ+ (2<δ<4) and Ce3+ -Ov are revealed by quasi in situ X-ray photoelectron spectra and in situ electron paramagnetic resonance spectra. Moreover, in situ Fourier-transform infrared spectra of D2 O photodissociation and desorption verify the existence of the Pd-OD bond, implying that Pdδ+ sites can participate in water oxidation to deliver H* species for facilitating the protonation of the intermediates. Furthermore, theoretical calculations suggest the Pd doping could regulate the formation energy barrier of the key intermediates CO* and CH3 O*, thus making CO2 reduction to CH4 become the favorable process. Accordingly, Pd-doped CeO2 nanosheets achieve nearly 100 % CH4 selectivity of CO2 photoreduction, with the raising CH4 evolution rate of 41.6 µmol g-1 h-1 .

Industrial-Current-Density CO2-to-C2+ Electroreduction by Anti-swelling Anion-Exchange Ionomer-Modified Oxide-Derived Cu Nanosheets.

CO2 electroreduction to high-energy-density C2+ products is highly attractive, whereas the C2+ selectivity under industrial current densities is still unsatisfying. Here, an anti-swelling anion exchange ionomer (AEI) was first proposed to optimize the local environment for promoting industrial-current-density CO2-to-C2+ electroreduction. Taking the anti-swelling AEI-modified oxide-derived Cu nanosheets as an example, in situ Raman spectroscopy and contact angle measurements revealed that the OH--accumulated -N(CH3)3+ groups and anti-swelling backbone of AEI could synergistically regulate the local pH level and water content. In situ Fourier-transform infrared spectroscopy and theoretical calculations demonstrated that the higher local pH value could lower the energy barrier for the rate-limiting COCO* hydrogenated to COCOH* from 0.08 to 0.04 eV, thereby boosting the generation of C2+ products. Owing to the anti-swelling backbone, the optimized water content of 3.5% could suppress the competing H2 evolution and hence facilitate the proton-electron transfer step for C2+ production. As a result, the anti-swelling AEI-modified oxide-derived Cu nanosheets achieved a C2+ Faradaic efficiency of 85.1% at a current density up to 800 mA cm-2 with a half-cell power conversion efficiency exceeding 50%, outperforming most reported powder catalysts.

Surface Engineering on Commercial Cu Foil for Steering C2H4/CH4 Ratio in CO2 Electroreduction.

Designing catalysts with high selectivity toward C2 products in CO2 electroreduction is crucial to energy storage and sustainable development. Here, we propose a Cu foil kinetic model with abundant nanocavities possessing higher reaction rate constant k to steer the ratio of C2H4 to the competing CH4 during CO2 electroreduction. Chemical kinetic simulation demonstrates that the nanocavities could enrich the adsorbed CO surface concentration (θCOad), while the higher k helps to lower the C-C coupling barrier for CO intermediates, thus favoring the formation of C2H4. The commercial Cu foil treated with cyclic voltammetry is used to match this model, displaying a remarkable C2H4/CH4 ratio of 4.11, which is 18 times larger than that on the pristine Cu foil. This work offers a handy strategy for surface modification and provides new insights into the C-C coupling and the C2H4 selectivity in terms of mass transfer flux and energy barrier.

Rational design of electrocatalytic carbon dioxide reduction for a zero-carbon network.

Electrocatalytic CO2 reduction has attracted much attention for its potential application in CO2 mitigation and fuel production. During the past two decades, the electrocatalytic reduction of CO2 has made considerable progress, and it has become a promising tool to answer environmental problems. However, most research into electrocatalytic CO2 reduction focuses on catalysts at the material level instead of evaluating the performance of the entire system for practical applications, which is insufficient to promote the sound development. This review emphasizes on how to rationally design an electrocatalytic CO2 reduction system. We initially demonstrate the necessity of electrocatalytic CO2 reduction and establish its economic analysis, and at the same time provide an overview of representative breakthroughs in this field. Then, we combine with advanced characterization technologies to deeply understand the reaction pathways of electrocatalytic CO2 reduction at the molecular level. Furthermore, we point out how theoretical guidelines enable the rational design of high-throughput catalysts and the synergistic promotion of electrocatalytic CO2 reduction performance by optimizing the electrocatalytic interface and the reactor. Finally, we customize impartial recommendations and criteria for electrocatalytic CO2 reduction to promote its healthy development. We hope to stimulate high-quality research and may see the future application of electrocatalytic CO2 reduction to solve sustainable energy and environmental problems.