Non-metallic Materials Research Articles

Non-destructive testing for thickness measurement of the adhesive layer and defect detection in ceramic-metal bonded structures using THz waves

Ceramics, owing to their superior thermal barrier properties, are employed by bonding them to primary structures exposed to elevated temperatures, such as the external components of aircraft and spacecraft. However, when these bonded structures are subjected to thermal impact resulting from high-temperature environments or rapid temperature variations, issues such as debonding, crack formation, and degradation may ensue. These issues can significantly undermine the reliability of the structures, necessitating nondestructive testing (NDT) to monitor the condition of the adhesive layer before and after thermal impact. In this article, we evaluated the integrity of adhesive structures before and after thermal impact using Terahertz (THz) waves, which offer exceptional penetration and resolution for NDT of nonmetallic materials without causing damage to the structure. To achieve this, ceramic-metal bonded structures were mounted on a robotic arm, and scanning was performed over a 70 mm area at 1 mm intervals and 0.5° increments. The peak-to-peak time of the THz signal through the adhesive layer was calculated to determine the thickness distribution. Based on experimental results, the average thickness of the ceramic layer before thermal shock was measured at 9.48 mm (standard deviation: 0.03) and the average thickness of the adhesive layer was 0.234 mm (standard deviation: 0.03). Additionally, four suspected defect areas within the adhesive layer were identified. After thermal shock, the ceramic layer’s thickness decreased by an average of 0.02 mm (0.17%), resulting in an average thickness of 9.46 mm, and the adhesive layer’s thickness decreased by an average of 0.002 mm (0.99%), resulting in an average thickness of 0.232 mm. The four suspected defect areas were confirmed to be in the same locations before thermal impact. To validate the NDT method using THz wave, the ceramic-metal bonded structure was cut to identify debonding defects in the suspected areas. The difference between the thickness distribution obtained using the THz wave-based NDT and that measured using optical microscopy after cutting was 4.4%, confirming the accuracy of the THz wave-based method for defect detection and thickness measurement.

Термомеханическая прокатка при производстве обсадных труб (обзор исследований)

Introduction. The modern oil and gas industry requires the development of high strength materials for well casing. Changes in rolled steel production technologies are one of the urgent tasks. Reducing the cost of high quality steel well casing is becoming a major challenge for the oil and gas industry. Multiphase microstructures containing acicular ferrite or an acicular ferrite-dominated phase exhibit good complex properties in HSLA steels. This paper focuses on the results obtained using modern methods of thermomechanical rolling. Results and discussion. This work analyzes the characteristics of thermomechanical rolling technologies and its impact on the microstructure of rolled steel for well casing. It is shown that predicting mechanical properties based on the microstructural characteristics of steel is complicated due to the large number of parameters involved. This requires an optimal microstructure of the steel. A satisfactory microstructure depends on several factors, such as chemical composition, hot work processing, and accelerated cooling. Alloying elements have a complex effect on the properties of steel, and alloying additives are usually introduced into the steel composition. From a metallurgical point of view, the choice of alloying elements and the metallurgical process can greatly influence the resulting microstructure. Conclusion. This review reports the most representative study regarding thermomechanical rolling technologies and microstructural factors in well casing steels. It includes a summary of the most important process variables, material properties, regulatory guidelines, and microstructural and mechanical properties of the metal for well casing production. This review is intended to benefit readers from a variety of backgrounds, from non-metal forming or materials scientists to various industrial application specialists and researchers.

Preparation of C-doped g-C3N4 by Co-polycondensation of melamine and sucrose for improved photocatalytic H2 evolution

g-C3N4, a well-known semiconductor is widely used for photocatalysis because of its renowned and special properties. It is a nonmetallic polymeric material that is abundant in sources and easy to prepare, making it an attractive choice for photocatalysis that responds to visible light. However, due to various intrinsic structural and chemical drawbacks, it is very far from further applications. Herein, we used sucrose to modify the physicochemical characteristics of ordinary g-C3N4 to prepare a carbon self-doped g-C3N4 (Cn-MA) material through co-polycondensation with melamine and applied it for hydrogen production. The characterization showed that the addition of sucrose resulted in a narrowed band gap, widened absorption range, enhanced photoresponse, and photogenerated charge carrier separation. Furthermore, the prepared material was applied for hydrogen production activity, which revealed that it has higher photocatalytic performance than pristine g-C3N4. The H2 production rate of the optimized material (C7.5-MA) was recorded as 7.3 times greater than that of pure g-C3N4. Through cycling tests, the stability of C7.5-MA was examined. The results showed that, even after four consecutive cycles, no apparent drop in its performance was observed. Additionally, here the mechanism of hydrogen production is also discussed.

PEEK Retainers without CAD-CAM: Simple Solutions for Everyday Challenges

Background: The need to perform occasional or continuous MRI exams and the interference with metal orthodontic appliances might be important and take a primary role during retention since the retention period is significantly longer than orthodontic treatment. Several non-metallic materials were proposed as potential alternatives to perform fixed retainers in orthodontics, but they showed internal limits. Methods: Polyetheretherketone (PEEK) was used in the present clinical report as a fixed orthodontic retainer in the lower arch in order to perform an appliance with mechanical properties comparable to metallic ones but with a higher biocompatibility material and without the need for removal in case of an MRI exam. The retainer wire was handmade in the studio and then shaped to fit the arch. Results: PEEK showed a good capability for constructing a lingual fixed retainer compared to other aesthetic non-metallic and metallic materials. Conclusions: To the best of our knowledge, this study proposes how to easily build a retainer in PEEK and provides a clinical example of how this material can be beneficial.

Frequency-domain axisymmetric and thermomechanical viscoelastic analysis of thermoplastic composite pipe

ABSTRACT Thermoplastic composite pipe (TCP), composed of polymers and composite laminates, shows significant potential for deep-water offshore oil field development due to its lightweight and high strength. However, current mechanical studies primarily focus on the elastic domain, ignoring the critical viscoelasticity of non-metallic materials. To solve this, we introduce a comprehensive theoretical model that incorporates viscoelastic properties under both axisymmetric and thermal loads, considering radial convective thermal gradients and axial heat conduction. This model accurately predicts TCP's mechanical behavior by using stiffness coefficients, differential geometry, and radial-axial temperature transfer curves. By applying the principle of elastic-viscoelastic correspondence, we obtain viscoelastic solutions in the frequency domain, showing strong agreement with Finite Element (FE) models particularly under cyclic loading. Viscoelasticity introduces larger equivalent axial stiffness and viscoelastic damping within complex structures, which become more obvious with temperature fluctuations.

Penetration Thresholds of Porcine Limbs for Low Sectional Density Projectiles in High-Rate Impact.

With similar prevalence to injuries from fires, stings, and natural disasters, soft tissue injuries may occur from fireworks, industrial accidents, or other explosives. Surgeons are less familiar with treating high-velocity penetration from small debris, which may increase the chance of infection and subsequent fatality. Penetration risk curves have been developed to predict V50, the velocity with 50% probability of penetration, for various sized projectiles. However, there has been limited research using nonmetallic materials to achieve lower density projectiles less than 1 g cm-2, such as sand or rocks. To emulate the size and density of these energized particles, 14 ball bearings of stainless steel, silicon nitride, or Delrin acetal plastic ranging from 1.59 mm (1/16") to 9.53 mm (3/8") with sectional densities between 0.3 g cm-2 and 5 g cm-2 were launched toward porcine legs at a range of velocities to determine the penetration thresholds. High-speed videography was captured laterally at 40 kHz and impact velocity was captured using a physics-based tracking software. A generalized linear model with repeated measures and a logit link function was used to predict probability of penetration for each projectile. A total of 600 impacts were conducted to achieve at least 15 penetrating impacts for each projectile over a range of velocities. Higher impact velocities were required to penetrate the skin as sectional density of the projectile decreased, and the relationship between velocity and sectional density exhibited an exponential relationship (V50, $ = 184.6*S{D^{ - 0.385}}$, R2 = 0.95) with substantial change for nonlinearity in sectional densities ranging from 0.3 g cm-2 to 1 g cm-2. Compared to previous studies, the empirical relationship was consistent in the linear region (2-5 g cm-2), and novel experimentation filled in the gaps for sectional densities less than 1 g cm-2, which expressed more nonlinearity than previously estimated. For low-density projectiles with diameters of 1.59 (1/16") or 3.18 (1/8"), 32 impacts were lodged into the epidermis but did not penetrate through the dermis; however, penetration was defined as displacement into or through the dermis. These experimental results may be used to develop and validate finite element simulations of low-density projectile impacts to address complex, multivariate loading conditions for the development of protective clothing to reduce wounding and subsequent infection rates.

Surface plasmon resonance (SPR)-enhanced photocatalytic degradation by periodically ordered δ-MnO2 arrays with alkali metals doping

Periodically ordered δ-MnO2 arrays of different periods have been fabricated by using polystyrene (PS) nanosphere lithography (NSL) combined with following hydrothermal growth. By choosing different precursors, δ-MnO2 arrays with different alkali metals doping were obtained. It was observed that the K-doped δ-MnO2 array of 500 nm period exhibited superior photocatalytic degradation performance of methylene blue (MB) under visible light irradiation relative to those of Na- or Mg-doped δ-MnO2 arrays of 500 nm period, as well as K-doped δ-MnO2 array of 800 nm period. The best performance of K-doped δ-MnO2 array of 500 nm period can be firstly attributed to enhanced surface plasmon resonance (SPR) effect caused by alkali metal doping, where K-doped MnO2 could provide more free electrons than those of Na- or Mg- doped MnO2. Furthermore, for the nanomaterials with SPR effect the surface plasmon polaritons (SPP) can change the propagation path of incident light to vertical direction after scattering on them. Since the MnO2 array of 500 nm period possessed the distance between neighbor unites smaller than the wavelength of irradiation light, and thus the scattered light interfered with each other after the incident light was scattered by the MnO2 unites. Then the electric field (E-field) intensities generated by SPR effect near each MnO2 unit were elevated due to the interference effect. Therefore, our finding may provide a peculiar way to improve SPR-mediated photocatalytic performance of non-metallic materials by combination of doping and arrays fabrication of particular periods.

Assessment of structural materials containing notch-type defects: A comprehensive validation of the FAD-TCD methodology on metallic and non-metallic materials

This paper provides a comprehensive description, and the subsequent validation, of a structural integrity assessment methodology of structural materials containing notch-type defects. The approach is based on the combination of Failure Assessment Diagrams (FAD) and the Theory of Critical Distances (TCD). The former provides the general assessment tool, which is exactly the same one as that used for crack-like defects, whereas the latter provides the notch effect correction required for the analysis of this type of defects. Finally, the proposed methodology is validated on a number of metallic and non-metallic structural materials, with 1,106 experimental results on different types of testing specimens, covering four structural steels, aluminium alloys 7075-T651 and 6060-T66, PVC, PMMA, PA6, fibre-reinforced PA6, 3D printed (Fused Filament Fabrication) ABS, PLA and graphene reinforced PLA, granite and limestone. The results show how the FAD-TCD methodology provides safe reasonably conservative assessments on the mentioned structural materials in the presence of notch-type defects.

Increasing the strength of potato digger elevator rods

Abstract Currently, high-quality steels are used to increase the reliability of potato digging machines and the durability of elevator rods. Recently, new materials, new technologies and non-metallic materials that are not inferior in strength to steel have been used in agricultural machines. Such materials significantly reduce the mass of the working parts. This article examines the deformation of a new elevator rod design due to the action of soil and tuber-bearing mass. The rods, covered with double-cavity rubber profiles, vibrate the component of the potato heap. During vibrations, in addition to static deformations, dynamic deformations occur, depending on the magnitude of the impact force. As a result, it was found that to eliminate the loss of tubers between the bars of the separating elevator, given the maximum deflection value of 0.03 m and the weight of the soil-tuber-bearing mass, the rubber bar must have the following parameters: elasticity model E = 50 N/mm2; rod perimeter 11x11 mm; the maximum jump height of a mass weighing 130 kg is no more than 0.6 m.

Machine Learning Applied to Terahertz Signal Analysis For Hygrothermal Aging Characterization of Composites

Given their noncontact nature, ease of inspecting nonmetallic materials, and ability to detect small structural changes, terahertz waves were chosen as the study methodology for this project. Initially, characterization data was pretreated and standardized. The data were then reduced in dimensionality using principal component analysis and classified using other machine learning methods. The results demonstrated that the terahertz wave technique could accurately distinguish between different temperature and aging time scenarios. They also indicated that nondestructive in-service characterization of composite repairs is feasible and can provide invaluable information for decision-making. The main benefits of this approach include ensuring the safe operation of offshore piping and optimizing resources when deciding whether to replace the repair or keep it in service.

Concealed hazardous object detection for terahertz images with cross-feature fusion transformer

Terahertz (THz) waves can penetrate many non-metallic materials (such as paper, plastic, and clothing), making them highly valuable in security inspection areas. However, the low contrast between target objects and the background in THz images poses problems for object detection and recognition tasks. Though many schemes have been proposed to tackle the problems, the low detection accuracy and high computational complexity remain challenges. To address these challenges, we propose a concealed hazardous object detection method called Cross-Feature Fusion Transformer YOLO (CFT-YOLO) for THz images. We design a Multi-Channel Spatial Feature Module (MCSFM) to achieve cross-channel and cross-spatial information transfer between feature maps. MCSFM also realizes the feature parameter transfer between the backbone and neck of the network. Additionally, we develop a CrossFuse-Transformer (CF-Former) module that leverages self-attention to fully exploit the correlations and structural information between different feature maps. We conduct a series of experiments on public datasets. The results show that CFT-YOLO outperforms the other advanced methods in THz hazardous object detection tasks. Moreover, the CFT-YOLO achieves a better balance between model complexity and detection accuracy compared to YOLOv8s, making it more practical for real-world applications.

Assessment of Surface Roughness of Non-Metallic Materials during Laser Processing

Experimental studies of the surface of non-metallic materials have been carried out to determine the roughness parameters of materials such as leather, bone, wood, plastic after processing the surface of materials with a laser beam. To assess the quality of the surface layer of materials, the depth of penetration of laser radiation into the material, the average value of the micro unevenness, and the mean square deviation of the micro unevenness were used. To describe the changes in the values of the micro unevenness, graphs of the correlation of the parameters of the micro unevenness and the modulus of elasticity of the surface of various non-metallic materials were used. Approximating polynomials are used to describe the correlations with the representation in a computer. A regression model is proposed that relates the properties of the material to the magnitude of the micro unevenness. Data on the depth of ablation for wood, bone, leather, plexiglass are presented, graphs of the correlation between the amount of surface micro unevenness and the density of materials, between the amount of surface micro-roughness and the modulus of elasticity of materials, the correlation coefficient between the amount of surface micro unevenness and the ignition temperature of organic materials. The obtained models make it possible to implement the proposed principle of laser processing of non-metallic materials, which consists in measuring the modulus of elasticity of the surface of the material and, based on the measurements obtained, control the modes of laser processing of products. The installation of laser surface treatment of non-metallic materials with the implementation of the principle of control of processing modes depending on the measured values of the modulus of elasticity of the surface of the material is proposed. To measure the elastic modulus of a material, a special sensor is used with indentation of the indenter and computer evaluation of the measurements obtained with the formation of solutions for controlling the modes of laser surface treatment of the material. The experimental results obtained made it possible to manufacture a number of products to ensure a given surface quality of non-metallic materials (a writing device, a gift for the newlyweds). Conducting experiments with changes in the power of laser radiation based on the results of measuring the modulus of elasticity of the surface of non-metallic materials has shown the effectiveness of operational setting of laser operating modes to ensure the quality of the surface of non-metallic materials.

Energy band engineering of graphitic carbon nitride for photocatalytic hydrogen peroxide production

AbstractHydrogen peroxide (H2O2) is one of the 100 most important chemicals in the world with high energy density and environmental friendliness. Compared with anthraquinone oxidation, direct synthesis of H2O2 with hydrogen (H2) and oxygen (O2), and electrochemical methods, photocatalysis has the characteristics of low energy consumption, easy operation and less pollution, and broad application prospects in H2O2 generation. Various photocatalysts, such as titanium dioxide (TiO2), graphitic carbon nitride (g‐C3N4), metal‐organic materials, and nonmetallic materials, have been studied for H2O2 production. Among them, g‐C3N4 materials, which are simple to synthesize and functionalize, have attracted wide attention. The electronic band structure of g‐C3N4 shows a bandgap of 2.77 eV, a valence band maximum of 1.44 V, and a conduction band minimum of −1.33 V, which theoretically meets the requirements for hydrogen peroxide production. In comparison to semiconductor materials like TiO2 (3.2 eV), this material has a smaller bandgap, which results in a more efficient response to visible light. However, the photocatalytic activity of g‐C3N4 and the yield of H2O2 were severely inhibited by the electron‐hole pair with high recombination rate, low utilization rate of visible light, and poor selectivity of products. Although previous reviews also presented various strategies to improve photocatalytic H2O2 production, they did not systematically elaborate the inherent relationship between the control strategies and their energy band structure. From this point of view, this article focuses on energy band engineering and reviews the latest research progress of g‐C3N4 photocatalytic H2O2 production. On this basis, a strategy to improve the H2O2 production by g‐C3N4 photocatalysis is proposed through morphology control, crystallinity and defect, and doping, combined with other materials and other strategies. Finally, the challenges and prospects of industrialization of g‐C3N4 photocatalytic H2O2 production are discussed and envisioned.

Technology Focus: Wellbore Tubulars (July 2024)

The oil and gas industry has witnessed significant advancements in downhole technology, driving improved efficiency, sustainability, and well integrity. The technical papers here offer valuable insights into these developments, exploring nonmetallic downhole tubulars, collaborative ecosystems, material selection, environmental sustainability, and mechanical evaluation, showing a promising alternative to traditional steel counterparts. Paper SPE 214647 explores operational experiences with glass-reinforced-epoxy-lined tubing, highlighting significant benefits such as corrosion protection, cost savings, and improved well integrity. The journey from pilot to large-scale implementation reveals valuable insights into the technology’s evolution and challenges faced by operators. Complementing this, paper IPTC 23491 emphasizes the pivotal role of ecosystem partners in realizing nonmetallic tubulars. It underscores the need for multidisciplinary collaboration across academia, research institutes, manufacturers, and service providers to navigate challenges and drive innovation effectively. Paper IPTC 23549, included in the recommended reading list, delves into materials and construction aspects critical for successful deployment. It discusses the selection of nonmetallic materials, pipe-construction considerations, and the importance of standardization to meet stringent downhole requirements, signaling a path toward product development and commercialization. Concurrently, paper SPE 214488 addresses mechanical evaluations and interventions in nonmetallic tubulars, showcasing advancements in testing methodologies and tool deployment. Insights gleaned from these evaluations inform future research and development efforts to enhance product reliability and performance. Finally, the carbon life-cycle assessment of nonmetallic tubulars in recommended-reading paper IPTC 24122 underscores environmental sustainability as a driving force behind innovation. By evaluating carbon footprints and life-cycle effects, the industry seeks to adopt ecofriendly solutions without compromising operational efficiency. The synthesis of these papers underscores the transformative potential of nonmetallic downhole tubulars in reshaping oilfield operations. Through collaborative partnerships, material advancements, rigorous testing, and environmental considerations, the industry strives toward safer, more-sustainable, and more-cost-effective solutions. Recommended additional reading at OnePetro: www.onepetro.org. IPTC 23549 Making Nonmetallic Downhole Tubulars a Reality—Materials and Construction by Serena L.M. Goh, Baker Hughes, et al. IPTC 24122 Carbon Life-Cycle Assessment of Nonmetallic Downhole Tubulars by P. Sarmah, Baker Hughes, et al.

BENCH HIGHT AND SLOPE ANGLE ON LITHIUM ORES OPEN PIT MINES

The fundament of the open pit geometry, both, on metallic and non-metallic mineral raw materials, consists of benches that allow mining operations to be carried out in the contour of the open pit mine. On lithium pit mines, formed benches of a certain height and slope angle, must ensure physical stability of the open mine pit and smooth running of mining work to excavate, load and transport the overburden and mineral resources out of the contour of the lithium open pit mine. The bench height and slope (bank) angle depend on the geotechnical situations, water impact and conditions of utilizing mining mechanization in digging, loading and transporting the overburden and mineral raw material. Key words: lithium, open pit mine, bench height, bench slope angle

Effect of quartz sand addition on pore formation mechanism of blast furnace slag microcrystalline cast stone

Microcrystalline cast stone is a silicate inorganic nonmetallic material prepared via a melting–casting–crystallization process using slag as the main raw material and appropriate nucleating, quenching, and tempering agents. However, crystallization of the microcrystalline cast stone causes overall shrinkage, producing defects such as holes on the surface and inside and affecting the quality and yield. In this work, the effect of quartz-sand addition on the formation of voids in microcrystalline cast stone prepared from blast-furnace slag is studied. The theoretical composition, phase transformation, and microstructure of microcrystalline cast stone are analyzed through FactSage thermodynamic calculations, X-ray diffraction, and scanning electron microscopy. The results show that the main crystal phases in the microcrystalline cast stone are gehlenite and akermanite for 5, 7, 8, and 10 % quartz-sand addition. When the amount of quartz sand added is 8 %, the overall shrinkage rate of the ordinary augite phase is 16 %. The maximum amount of dicalcium silicate is formed, filling the holes on the surface and inside and inhibiting the formation of holes. The crystal morphology is snowflake-like and the crystal connections are dense. The flexural strength reaches a maximum value of 40.08 MPa, which improves the overall performance of the microcrystalline cast stone. The results of this study can provide technical support for improving the yield and quality of microcrystalline cast stone prepared by melting.

A Water Environment-Based Simulated Method for Ultrasonic Testing of Slag Inclusion Weld Defects Based on Improved VMD.

The identification of slag inclusion defects in welds is of the utmost importance in guaranteeing the integrity, safety, and prolonged service life of welded structures. Most research focuses on different kinds of weld defects, but branch research on categories of slag inclusion material is limited and critical for safeguarding the quality of engineering and the well-being of personnel. To address this issue, we design a simulated method using ultrasonic testing to identify the inclusion of material categories in austenitic stainless steel. It is based on a simulated experiment in a water environment, and six categories of cubic specimens, including four metallic and two non-metallic materials, are selected to simulate the slag materials of the inclusion defects. Variational mode decomposition optimized by particle swarm optimization is employed for ultrasonic signals denoising. Moreover, the phase spectrum of the denoised signal is utilized to extract the phase characteristic of the echo signal from the water-slag specimen interface. The experimental results show that our method has the characteristics of appropriate decomposition and good denoising performance. Compared with famous signal denoising algorithms, the proposed method extracted the lowest number of intrinsic mode functions from the echo signal with the highest signal-to-noise ratio and lowest normalized cross-correlation among all of the comparative algorithms in signal denoising of weld slag inclusion defects. Finally, the phase spectrum can ascertain whether the slag inclusion is a thicker or thinner medium compared with the weld base material based on the half-wave loss existing or not in the echo signal phase.

Heavy atom effect boosts the achievement of ultra-efficient long afterglow room temperature phosphorescent carbon point composites: An enhanced approach

In recent years, room temperature phosphorescent (RTP) materials have experienced rapid growth due to their enduring luminescence, high resolution, and other distinctive characteristics. Simultaneously, carbon dots (CDs) have gained popularity across various disciplines for their efficient luminescence, straightforward synthesis, and environmental friendliness. In this study, we successfully synthesized a range of high-performance carbon dot materials using a simple one-step hydrothermal method. Through detailed morphological and photophysical characterizations, we discovered that these materials exhibited a remarkable phosphorescence quantum yield of up to 53.15 %, an impressive feat for both metal and non-metal carbon dot materials. Furthermore, we explored the enhancing effect of the heavy atom on ultra-efficient long afterglow RTP carbon dot composites and experimentally validated its effectiveness. Finally, we applied these materials to information encryption technology, offering novel ideas and methods for RTP material applications. This research not only opens new avenues for the development of carbon dot materials but also provides a promising direction and outlook for their future use.

Micromechanical piezoelectric micromachined ultrasonic transducer array package enhancement with integrated frontliners

In order to improve the susceptibility of ultrasonic transducers to damage and the mismatch in acoustic impedance with test specimens, an impedance-matching layer is introduced between the transducer and the specimen. The impact of the matching layer on acoustic propagation of transducer was analyzed through acoustic field simulation. The performance of the improved transducer was experimentally evaluated by using a dedicated echo testing system for transducers. The matching layer was optimized by considering different materials. The results show that for non-metallic materials, only a layer of acoustic matching layer (organic silicone gel) can be added to achieve acoustic impedance matching and avoid wear. For metal materials, two acoustic matching layers (organic silicone gel and epoxy resin) need to be added to achieve acoustic impedance matching. The propagation efficiency of sound waves is increased by 30% as a result of this process.

Oxygen functionalized diamond nanocone arrays coupling cobalt phthalocyanine for enhanced electrochemical CO2 reduction

The development of high-efficiency catalysts plays a crucial role in advancing CO2 electroreduction techniques. Among potential candidates, diamond-based electrocatalysts show promise due to their broad electrochemical windows, which effectively suppress competitive hydrogen evolution and ensure high CO2 reduction efficiency. In this study, we report an integrated electrode composed of oxygen-terminated diamond nanocone (ODcone) with CoPc-molecules anchoring (CoPc/ODcone). The CoPc/ODcone electrodes exhibited remarkable performance, achieving a maximum Faradaic efficiency (FE) of 94.1% for CO at −0.97 V vs reversible hydrogen electrode (RHE), and maintaining an FECO higher than 80% over a wide potential range of −0.67 V to −1.07 V vs RHE. The outstanding performance of the CoPc/ODcone electrode can be attributed to the synergistic effects between the nanostructured diamond surface and the CoPc catalyst. The hydroxyl-rich nature of the diamond surface facilitates the anchoring of CoPc molecules and bonding with Co atoms in CoPc. Simultaneously, the nanostructured diamond with sharp tips enhances CO2 adsorption, thereby improving the catalyst's performance. This study provides valuable insights into the utilization of non-metallic carbon materials, particularly diamond, as metal-free catalysts in CO2 electrochemical reduction and tackles challenges such as low current density and poor Faradaic efficiency, thus contributing to the advancement of more effective catalysts for CO2 electroreduction.