Notch-insensitive, tough and self-healing conductive bacterial cellulose nanocomposite hydrogel for flexible wearable strain sensor.

To date, conductive hydrogels as an alternative to traditional rigid metallic conductors have attracted much attention in the field of flexible wearable electronic devices due to their inherent characteristics. Herein, a conductive bacterial cellulose (BC) nanocomposite hydrophobic-association (HA) hydrogel with highly stretchable, strong, self-healing, and notch-insensitive was fabricated by introducing the hydrophobic association. The obtained BCNC HA hydrogel shows excellent mechanical properties (∼ 2400 % of stress and âˆ¼ 0.35 MPa of mechanical strength), superior notch-insensitive property with a fracture energy of ∼38 KJ.m-2, and good self-healing property (healing efficiency of ∼97 %). In addition, the hydrogel exhibits excellent ionic conductivity of ∼1.90 S.m-1 and high sensing sensitivity toward tensile deformation. The wearable strain sensor based on this material is assembled can detect both large-scale motions and subtle body motions in real time, which show excellent durability (1000 cycles with the strain of 30 %). Thus, the BCNC HA hydrogels have promising potential in various wearable flexible electronic devices for artificial intelligence and human-machine interface applications in the future.

Predictive factors for iliac vein compression syndrome in patients with varicose veins.

OBJECTIVE: This study aimed to identify predictors of iliac vein compression syndrome (IVCS) in patients with varicose veins and to evaluate the necessity of routine lower extremity venography for preoperative assessment of these patients. METHODS: A retrospective analysis was conducted on data from 1165 patients with lower-limb varicose veins who underwent preoperative venography at Wuhan Union Hospital, Tongji Medical College, China, between January 2019 and September 2023. Logistic regression analyses identified factors associated with concurrent IVCS, and a nomogram was constructed based on these findings. RESULTS: Out of 1165 patients, 75 (6.4%) had IVCS according to venography and 769 had iliac vein ultrasound and found 2 (0.17%) positives. Multivariate analysis revealed the independent predictive value of left-sided involvement (odds ratio (OR) = 3.22, 95% confidence interval (CI): 1.24-8.33, p = 0.016), history of deep vein thrombosis (DVT) in the affected limb (OR = 3.11, 95% CI: 1.21-8.00, p = 0.018), pain (OR = 2.24, 95% CI: 1.17-4.26, p = 0.014), and positive results on iliac vein ultrasound (OR = 25.56, 95% CI: 2.10-311.26, p = 0.011) for the presence of IVCS in patients with lower-limb varicose veins. A nomogram incorporating these predictors demonstrated moderate predictive ability (AUV = 0.689, 95% CI: 0.607-0.771), with good calibration upon validation. CONCLUSIONS: Patients with left lower extremity varicose veins, pain symptoms, history of DVT in the affected limb, and positive iliac vein ultrasound findings are at a higher risk of concurrent IVCS. Patients with varicose veins who have the aforementioned risk factors may need to undergo preoperative angiography.

Lithium-Doped Titanium Dioxide-Based Multilayer Hierarchical Structure for Accelerating Nerve-Induced Bone Regeneration.

Despite considerable advances in artificial bone tissues, the absence of neural network reconstruction in their design often leads to delayed or ineffective bone healing. Hence, we propose a multilayer hierarchical lithium (Li)-doped titanium dioxide structure, constructed through microarc oxidation combined with alkaline heat treatment. This structure can induce the sustained release of Li ions, mimicking the environment of neurogenic osteogenesis characterized by high brain-derived neurotrophic factor (BDNF) expression. During in vitro experiments, the structure enhanced the differentiation of Schwann cells (SCs) and the growth of human umbilical vein endothelial cells (HUVECs) and mouse embryo osteoblast progenitor cells (MC3T3-E1). Additionally, in a coculture system, the SC-conditioned media markedly increased alkaline phosphatase expression and the formation of calcium nodules, demonstrating the excellent potential of the material for nerve-induced bone regeneration. In an in vivo experiment based on a rat distal femoral lesion model, the structure substantially enhanced bone healing by increasing the density of the neural network in the tissue around the implant. In conclusion, this study elucidates the neuromodulatory pathways involved in bone regeneration, providing a promising method for addressing bone deformities.

Circ_0003764 Regulates the Osteogenic Differentiation of Periodontal Ligament Stem Cells.

INTRODUCTION AND AIMS: Specific circular RNAs (circRNAs) have been proven to play crucial roles in osteogenesis in vitro and in vivo. This study aims to identify a certain circRNA involved in the osteogenic differentiation of periodontal ligament stem cells (PDLSCs) and explore its regulatory role. METHODS: The expression of 5 candidate circRNAs (circ_0026344, circ_ACAP2, circ_0003764, circ_0008259, and circ_0060731) was detected by real-time quantitative reverse-transcription polymerase chain reaction (qRT-PCR) after PDLSCs were cultured in the osteogenic induction medium or medium supplemented with tumour necrosis factor-α (TNF-α, 10 ng/mL) for 3 and 7 days. The circRNA significantly decreased in both 3 and 7 days of osteogenic induction in PDLSCs and markedly increased in TNF-α-induced PDLSCs for 3 and 7 days screened. Identified circRNA was knocked down or overexpressed, and the effect on the osteogenic differentiation of PDLSCs was investigated by qRT-PCR, western blot, alkaline phosphatase (ALP) staining, and alizarin red S (ARS) staining. Cell counting kit-8 (CCK-8) assay and 5-ethynyl-2'-deoxyuridine (EdU) assay were applied to detect the effect of the circRNA on the proliferation of PDLSCs. RESULTS: qRT-PCR results showed that the expression of circ_0003764 was significantly decreased when PDLSCs were cultured in the osteogenic induction medium for 3 or 7 days, whereas it was dramatically increased in TNF-α-induced PDLSCs. Knockdown of circ_0003764 promoted the expression of the osteogenesis-related genes (RUNX2, ALP, OCN) and proteins (RUNX2, OCN), enhanced the ALP activity, and elevated the mineralization by PDLSCs, as shown by ARS staining. However, with the overexpression of circ_0003764, the osteogenic differentiation capacity of PDLSCs was significantly reduced. The CCK-8 and EdU results indicated that circ_0003764 could inhibit the proliferation of PDLSCs. CONCLUSION: Circ_0003764 is involved in the osteogenesis process and inhibits the osteogenic differentiation and proliferation of PDLSCs. CLINICAL RELEVANCE: This study indicates that circ_0003764 can serve as a diagnostic and therapeutic target in bone regeneration-related diseases treated by PDLSCs-based tissue engineering.

Acute caval thrombosis leading to obstructive shock in the early post insertion period of an inferior vena cava filter: a case report and literature review.

BACKGROUND: Obstructive shock is extremely rare in clinical practice and is caused by acute blood flow obstruction in the central vessels of either the systemic or pulmonary circulation. Utilizing inferior vena cava filters (IVCFs) to prevent pulmonary embolism (PE) is associated with some potential complications, such as inferior vena cava thrombosis (IVCT). Shock as a direct result of IVCT is rare. We present a case of obstructive shock secondary to extensive IVCT caused by inadequate anticoagulant therapy after the placement of an IVCF. CASE PRESENTATION: A 63-year-old male patient with a traffic accident injury presented orthopaedic trauma and lower limb deep vein thrombosis (DVT). He experienced sudden and severe abdominal pain with hypotension, tachycardia, tachypnea, oliguria and peripheral oedema 5 days after IVCF placement and 3 days after cessation of anticoagulant therapy. Considering that empirical anti-shock treatment lasted for a while and the curative effect was poor, we finally recognized the affected vessels and focused on the reason for obstructive shock through imaging findings-inferior vena cava thrombosis and occlusion. The shock state immediately resolved after thrombus aspiration. The same type of shock occurred again 6 days later during transfer from the ICU to general wards and the same treatment was administered. The patient recovered smoothly in the later stage, and the postoperative follow-up at 1, 3, and 12 months showed good results. CONCLUSION: This case alerts clinicians that it is crucial to ensure adequate anticoagulation therapy after IVCF placement, and when a patient presents with symptoms such as hypotension, tachycardia, and lower limb and scrotal oedema postoperatively, immediate consideration should be given to the possibility of obstructive shock, and prompt intervention should be based on the underlying cause.

Improved Reversible Capacity and Cycling Stability by Linear (N=O) Anions in Fe[Fe(CN)5 NO] as Sodium-Ion Battery Cathode.

Prussian blue analogues (PBAs) are promising cathode materials for sodium-ion batteries (SIBs) due to their tunable chemistry, open channel structure, and low cost. However, excessive crystal water and volume expansion can negatively impact the lifetime of actual SIBs. In this study, a novel iron nitroprusside: Fe[Fe(CN)5 NO] (PBN) was synthesized to effectively eliminate the detrimental effects of crystal water on the reversible capacity and cycling stability of PBA materials. Experiments and DFT calculations demonstrated that PBN has lower crystal water and volume expansion compared to Fe[Fe(CN)6 ] (PB). Also, the N=O bond in PBN significantly reduces the diffusion potential of Na+ in the skeleton. Without any modification, the cathode material exhibited a capacity of up to 148.6 mAh g-1 at 50 mA g-1 as well as maintained 102.9 mAh g-1 after 200 cycles. This work expands our knowledge of the crystal structure of PBA cathode materials and facilitates the rational design of high-quality PBA cathodes for SIBs.

Kinetic Understanding of Catalytic Selectivity and Product Distribution of Electrochemical Carbon Dioxide Reduction Reaction.

CO2 can be electrochemically reduced to different products depending on the nature of catalysts. In this work, we report comprehensive kinetic studies on catalytic selectivity and product distribution of the CO2 reduction reaction on various metal surfaces. The influences on reaction kinetics can be clearly analyzed from the variation of reaction driving force (binding energy difference) and reaction resistance (reorganization energy). Moreover, the CO2RR product distributions are further affected by external factors such as electrode potential and solution pH. A potential-mediated mechanism is found to determine the competing two-electron reduction products of CO2 that shifts from thermodynamics-controlled product formic acid at less negative electrode potentials to kinetic-controlled product CO at more negative electrode potentials. Based on detailed kinetic simulations, a three-parameter descriptor is applied to identify the catalytic selectivity of CO, formate, hydrocarbons/alcohols, as well as side product H2. The present kinetic study not only well explains the catalytic selectivity and product distribution of experimental results but also provides a fast way for catalyst screening.

Long non-coding RNAs MALAT1 and NEAT1 in non-syndromic orofacial clefts.

Long non-coding RNAs (lncRNAs) are thought to play important roles in non-syndromic orofacial clefts (NSOFC). Clinical diagnosis was categorized as either non-syndromic cleft lip with or without cleft palate (NSCL/P), or non-syndromic cleft palate only (NSCPO). Tissues excised from the trimmed wound edge were reserved as experimental samples; adjacent normal control was used as a positive control, and tissue from healthy individuals was used as a blank control. Target lncRNAs in the collected tissues were identified using microarrays and quantitative reverse transcription PCR (RT-qPCR). Immunohistochemical (IHC) staining and RT-qPCR were used to verify the target mRNAs. Pathway, gene ontology (GO) enrichment, and TargetScan predictions were employed to construct competing endogenous RNA networks (ceRNA networks) and explore their potential functions. RNA-Seq revealed 24 upregulated and 43 downregulated lncRNAs; MALAT1 and NEAT1 were screened and validated using RT-qPCR. Common NSOFC risk factors were positively correlated with MALAT1 and NEAT1 expression. Bioinformatics predicted four ceRNA networks; GO enrichment focused on their potential functions. RT-qPCR and IHC data were consistent with respect to expression levels of proteins and the mRNAs that encode them. As MALAT1 and NEAT1 are associated with the severity of NSOFC, they represent potential therapeutic targets and prognostic biomarkers.

Green and sustainable cellulose-based shape memory composites with excellent conductivity for temperature warning.

Green and sustainable cellulose-based composites containing poly(ε-caprolactone) (PCL) with temperature-induced shape memory properties and conductivity performance are presented. The composites are fabricated by in situ polymerization of ε-caprolactone (ε-CL) monomer in three-dimensional porous cellulose gels, and then silver-porous cellulose gel/poly(ε-caprolactone) (Ag-Cell/PCL) composites are fabricated by depositing Ag onto the surface of porous cellulose gel/poly(ε-caprolactone) (Cell/PCL) composites. The addition of PCL not only improves the mechanical properties of the Cell/PCL composites but also endows them with excellent shape memory properties. The Cell/PCL composites exhibit a high shape-fixing rate (98.9%) and can recover to their original shape within 8 s without external force. In addition, the Ag-Cell/PCL composites show superior and stable conductivity under different bending angles. Finally, a temperature warning sensor with fast performance is successfully designed using Ag-Cell/PCL composites. This work provides a means to develop temperature warning systems based on shape memory polymers.

Periodontitis and Number of Teeth in the Risk of Coronary Heart Disease: An Updated Meta-Analysis.

BACKGROUND A positive link between periodontitis and chronic systemic disease has been indicated. However, few studies focused on the loss of teeth. Our analysis aims to analyze the relationship of periodontitis and number of teeth with the risk of coronary heart disease (CHD). MATERIAL AND METHODS A meta-analysis was conducted on qualified data extracted from the PubMed, Embase, and Cochrane Library databases. Only cohort studies were included in this study. We screened articles that assessed the periodontal condition and teeth number as well as the incidence or mortality of CHD. Hazard ratio (HR) and relative risk (RR) were calculated by Stata SE software. RESULTS A total of 11 prospective studies with over 200 000 total participants were analyzed. Ten studies reported on periodontitis and CHD, and 4 studies included data on number of teeth. After adjusting for multivariate factors, there was a significant association between periodontitis and the risk of CHD (RR, 1.18; 95% confidence interval [CI], 1.10-1.26); the RR of CHD in the edentulous population was 1.20 (95% CI, 1.08-1.34). Moreover, results on the RR values for number of teeth were as follows: 24-17 teeth (RR, 1.12; 95% CI, 1.05-1.19); 16-11 (RR, 1.28; 95% CI, 1.15-1.42); and £10 (RR, 1.55; 95% CI, 1.43-1.69). CONCLUSIONS Our study showed that periodontitis is a risk factor for CHD and that the number of removed teeth is positively correlated with the risk of CHD. During clinical assessment, both factors need to be considered as factors associated with cardiovascular risks.

Structural characteristics of small-molecule inhibitors targeting FTO demethylase.

Studies have shown that the FTO gene is closely related to obesity and weight gain in humans. FTO is an N6-methyladenosine demethylase and is linked to an increased risk of obesity and a variety of diseases, such as acute myeloid leukemia, type 2 diabetes, breast cancer, glioblastoma and cervical squamous cell carcinoma. In light of the significant role of FTO, the development of small-molecule inhibitors targeting the FTO protein provides not only a powerful tool for grasping the active site of FTO but also a theoretical basis for the design and synthesis of drugs targeting the FTO protein. This review focuses on the structural characteristics of FTO inhibitors and discusses the occurrence of obesity and cancer caused by FTO gene overexpression.

Potential roles of N6-methyladenosine (m6A) in immune cells.

N6-methyl-adenosine (m6A) is one of the most common internal modifications on RNA molecules present in mammalian cells. Deregulation of m6A modification has been recently implicated in many types of human diseases. Therefore, m6A modification has become a research hotspot for its potential therapeutic applications in the treatment of various diseases. The immune system mostly involves different types of immune cells to provide the first line of defense against infections. The immunoregulatory network that orchestrate the immune responses to new pathogens plays a pivotal role in the development of the disease. And m6A modification has been demonstrated to be a major post-transcriptional regulator of immune responses in cells. In this review, we summarize the participants involved in m6A regulation and try to reveal how m6A modification affects the immune responses via changing the immunoregulatory networks.

The lncRNA MEG3/miR-16-5p/VGLL4 regulatory axis is involved in etoposide-induced senescence of tumor cells.

BACKGROUND: The senescence of tumor cells is an important tumor suppressor mechanism. The present study aimed to investigate the role of long non-coding RNA (lncRNA) MEG3 (maternally expressed gene 3) in the senescence process of tumor cells and its potential molecular mechanism by competitively binding with microRNA miR-16-5p to regulate the expression of VGLL4 (encoding vestigial like family member 4). METHODS: We used etoposide to construct senescence models of tumor cells. The degree of cellular senescence was detected by senescence-associated ß-galactosidase, cell cycle and senescence-associated secretory phenotype. The expression of lncRNA MEG3, miR-16-5p and VGLL4 in senescent or non-senescent cells was evaluated using a quantitative real-time reverse transcriptase-PCR (qRT-PCR) or western blotting. Dual luciferase reporter assays were used to detect the binding of miR-16-5p to lncRNA MEG3 and VGLL4. The mRNA and protein expression levels of senescence-related markers (p53, p21 and p16) were detected using qRT-PCR or western blotting. RESULTS: Compared to the control group, the expression of lncRNA MEG3 and VGLL4 was significantly up-regulated in senescent cells. Knockdown of lncRNA MEG3 and VGLL4 reduced the degree of senescence and the expression of p21 and p16. lncRNA MEG3 interfered with the expression of miR-16-5p in senescent A549 and MCF-7 cells. The expression of VGLL4 was regulated by miR-16-5p in senescent A549 and MCF-7 cells. lncRNA MEG3 participated in the senescent progress of tumor cells induced by etoposide via the miR-16-5p/VGLL4 axis. CONCLUSIONS: The present study has confirmed the regulatory role of the lncRNA MEG3/miR-16-5p/VGLL4 axis in the low-dose etoposide-induced tumor cell senescence model, which has potential clinical application with respect to treating malignant tumors.

The role of chlorine atom on the binding between acrylonitrile derivatives and fat mass and obesity-associated protein.

In this work, seven acrylonitrile derivatives were selected as potential inhibitors of fat and obesity-related proteins (FTO) by the aid of fluorescence spectroscopy, ultraviolet visible spectroscopy, molecular docking, and cytotoxicity methods. Results show that the interaction between 3-amino-2-(4-chlorophenyl)-3-phenylacrylonitrile (1a) and FTO was the strongest among these derivatives. Thermodynamic analysis and molecular modeling show that the main force between 1a and FTO is hydrophobic interaction. The cytotoxicity test showed that the IC50 value of 1a was 46.64 µmol/L, which indicated 1a had the smallest IC50 value and had the best inhibitory effect on the proliferation of leukemia K562 cells among the seven derivatives. Both our previous results and this work show that chlorine atoms play important role in the binding of small molecules and FTO. This work brings new information for the study of FTO inhibitors.

A novel xanthan gum-based conductive hydrogel with excellent mechanical, biocompatible, and self-healing performances.

Tough and conductive hydrogels are promising materials for various applications. However, it remains a great challenge to develop an integrated hydrogel combining outstanding mechanical, conductive, and self-healing performances. Herein, we prepared a conductive, self-healing, and tough hydrogel by constructing synergistic multiple interaction among montmorillonite (MMT), Poly (acrylamide-co-acrylonitrile) (P(AAm-co-AN)), xanthan gum (XG) and ferric ion (Fe3+). The obtained xanthan gum/montmorillonite/Poly (acrylamide-co-acrylonitrile) (XG/MMT/PAAm) hydrogels showed high strain stress (0.48 MPa) and compressive stress (5.9 MPa) as well as good shape recovery after multiple loading-unloading cycle tests. Moreover, the XG/MMT/PAAm hydrogels have distinctive features such as remarkable resistance to fatigue and harsh environments, insensitivity to notch, conductive, biocompatible, pH-dependent swelling behaviors and self-healing. Therefore, the as-fabricated hydrogel delivers a new prospect for its applications in various fields, such as flexible conductive device and tissue engineering.

Tissue mechanics and expression of TROP2 in oral squamous cell carcinoma with varying differentiation.

BACKGROUND: Trophoblast cell surface antigen 2 (TROP2) is overexpressed in many squamous cell carcinomas and promotes tumor development and invasion. The association between TROP2 expression and occurrence and development of oral squamous cell carcinoma (OSCC) remains to be understood. METHODS: We investigated the role of TROP2 in OSCC patients using a combination of biophysical approaches. A total of 108 OSCC patient specimens with varying degrees of differentiation were subjected to hematoxylin and eosin staining, immunohistochemistry, Kaplan-Meier survival curve analysis, and atomic force microscopy to analyze TROP2 expression, morphology, and mechanical properties of OSCC tissues. RESULTS: TROP2 was overexpressed in 34% of poorly differentiated OSCC samples. High levels of TROP2 were associated with 10.2% survival rate lower than 45.4% and patient age (odds ratio [OR] = 0.437, P = 0.039, 95% confidence interval [CI, 0.198-0.966]), tumor size (OR = 13.148, P = 0.000, 95% CI [5.060-34.168]), and TNM stage (OR = 0.141, P = 0.000, 95% CI [0.082-0.244]). Average surface roughness of low, medium, and highly differentiated OSCC tissues were 448.9 ± 54.8, 792.7 ± 83.6, and 993.0 ± 104.3 nm, respectively. The Pearson coefficient revealed a negative association between tumor stiffness and TROP2 expression (r = - 0.84, P < 0.01). CONCLUSION: Overexpression of TROP2 negatively associated with patient survival, degree of tumor differentiation, and tissue mechanics. Taken together, our findings demonstrated that TROP2 may be an indicator of OSCC differentiation leading to the altered mechanical properties of OSCC tissues.

Virtual versus jaw simulation in Oral implant education: a randomized controlled trial.

BACKGROUND: This research aims to investigate the evaluation methods of teaching oral implant clinical courses and estimate the effectiveness of a virtual simulation platform. METHODS: Eighty second- and third-year undergraduates in Lanzhou University were recruited and randomized to either three experimental groups or one control group. The subjects undertook theoretical examinations to test their basic level of knowledge after training in similarly unified knowledge courses. Each student group then participated in an eight-hour operating training session. An operation test on pig mandible was conducted, followed by a second theoretical examination. The assessment consists of three distinct parts: a subjective operating score by a clinical senior teacher, an implant accuracy analysis in cone-beam computed tomography (angular, apical, and entrance deviation), and comparison of the two theoretical examinations. Finally, students completed a questionnaire gauging their understanding of the virtual simulation. RESULTS: There was no significant difference between the four groups in first theoretical examination (P > 0.05); the second theoretical scores of the V-J and J-V group (62.90 ± 3.70, 60.05 ± 2.73) were significantly higher than the first time (57.05 ± 3.92, P < 0.05), while no difference between the V (57.10 ± 3.66) and J (56.89 ± 2.67) groups was found. Thus, the combination of V-J was effective in improving students' theoretical scores. The V-J and J-V groups had higher scores on operation (73.98 ± 4.58, 71.85 ± 4.67) and showed better implant precision. CONCLUSION: Virtual simulation education, especially with a jaw simulation model, could improve students' implantology achievements and training. Currently study found that the V-J group may performed better than the J-V group in oral implant teaching.

Biomimetic Durable Multifunctional Self-Cleaning Nanofibrous Membrane with Outstanding Oil/Water Separation, Photodegradation of Organic Contaminants, and Antibacterial Performances.

Wastewater pollution has always been one of the most severe worldwide environmental problems. In addition, in light of the frequent oil spills that have occurred in recent years, the treatment of oily wastewater is particularly important. In this work, a novel zeolitic imidazolate framework-8@thiolated graphene (ZIF-8@GSH) composites-based polyimide (PI) nanofibrous membrane was developed via a facile electrospinning and in situ hydrothermal synthesis approaches for effective purification of oily wastewater. The membrane showed superhydrophobicity/superoleophilicity and high separation efficiency (>99.9%) for a wide range of oil/water mixtures and water-in-oil emulsions. Besides, the membrane demonstrated excellent photocatalytic dye degradation, antibacterial, self-cleaning, and mechanochemical durable abilities, showing high potential in oily wastewater treatment and water remediation.

Faithful Fabrication of Biocompatible Multicompartmental Memomicrospheres for Digitally Color-Tunable Barcoding.

Barcodes have attracted widespread attention, especially for the multiplexed bioassays and anti-counterfeiting used toward medical and biomedical applications. An enabling gas-shearing approach is presented for generating 10-faced microspherical barcodes with precise control over the properties of each compartment. As such, the color of each compartment could be programmatically adjusted in the 10-faced memomicrospheres by using pregel solutions containing different combinations of fluorescent nanoparticles. During the process, three primary colors (red, green, and blue) are adopted to obtain up to seven merged fluorescent colors for constituting a large amount of coding as well as a magnetic compartment, capable of effective and robust high-throughput information-storage. More importantly, by using the biocompatible sodium alginate to construct the multicolor microspherical barcodes, the proposed technology is likely to advance the fields of food and pharmaceutics anti-counterfeiting. These remarkable properties point to the potential value of gas-shearing in engineering microspherical barcodes for biomedical applications in the future.

Theoretical understanding of the electrochemical reaction barrier: a kinetic study of CO2 reduction reaction on copper electrodes.

The electrochemical reduction of CO2 is a promising route for converting intermittent renewable energy into storable fuels and useful chemical products. A theoretical investigation of the reaction mechanism and kinetics is beneficial for understanding the electrocatalytic activity and selectivity. In this report, a kinetic model based on Marcus theory is developed to compute the potential-dependent reaction barrier of the elementary concerted proton-electron transfer steps of electrochemical CO2 reduction reactions, different from the previous hydrogen atom transfer model. It is found that the onset potentials and rate-determining steps for CO and CH4 formation are determined by the first and third concerted proton-electron transfer steps C1 and C3. The influence of binding energy, electrode potential, and reorganization energy on the computed reaction barriers of the C1 and C3 reactions is discussed. In general, the calculated reaction barrier shows a quadratic relationship with the applied electrode potential. Specifically, the reaction barrier is merely determined by the reorganization energy at equilibrium potential. The present kinetic model is applied to compare the electrocatalytic activities in the electrochemical reduction of CO2 on various copper crystal surfaces. Among the four studied copper single-crystal surfaces, Cu(211) exhibits the best electrocatalytic activity for CO formation and CH4 formation due to its low onset potential and overpotential.