Cu-based Materials Research Articles

Copper electrocatalyst modified with pyridinium-based ionic liquids for the efficient synthesis of ethylene through electrocatalytic CO2 reduction reaction

Reducing carbon dioxide (CO2) emissions from industrial production and improving carbon capture and utilization have emerged as focal points in engineering disciplines. This study focuses on electrochemical catalysis for converting CO2 into valuable raw materials, with the aim of enhancing the selectivity and productivity of high value-added multi-carbon (C2+) products. To address limitations associated with copper cathodes such as low selectivity for ethylene (C2H4) product, low catalytic activity, and high energy consumption during CO2 reduction reaction (CO2RR), pyridinium-based ionic liquids (PyILs) are employed as modifiers for the cathode material. Flow cell is utilized to conduct CO2RR experiment and evaluate the catalytic properties of gas diffusion electrode (GDE) loaded with PyILs modified Cu-based materials (Cu@PyILs). The results suggest that the incorporation of PyILs layers enhances conductivity and facilitates high current density in flow cell. At a cathodic potential of −1.15 V (vs. RHE), Cu@[BPy]Br-2.4 exhibits the highest Faradaic efficiency for C2H4 (FEC2H4 = 31.88 %) and achieves a high current density of 275 mA·cm−2. Additionally, Cu@[BPy]BF4-2.4 and Cu@[BPy]PF6-2.4 exhibit FEC2H4 values surpassing 25 %. Meanwhile, the hydrogen evolution reaction (HER) in the flow cell is effectively suppressed, resulting in a FEH2 below 40 %. The present study highlights the exceptional catalytic activity of Cu@PyILs in CO2RR, demonstrating an enhanced selectivity towards C2H4 production. The findings suggest that PyILs have great potential as electrode modifiers.

Different surfaces of copper with single-atom doping for hydrogen evolution reaction in alkaline conditions

The advantages of Cu-based materials make it a potential catalyst for alkaline hydrogen production reactions (HER), but the inertness of pure Cu restricts its application. Thus, it is very meaningful to seek strategies to improve the catalytic activity. In this work, we designed the 15 modified Cu surface models by integrating single atom doping with surface engineering to be used to explore the catalytic activity of Cu surfaces in alkaline HER and the mechanism of effective adsorption and dissociation of water. The results indicated that the combination of surface engineering with single-atom doping can greatly activate the electro-catalysis activity of copper surface. All these 15 catalysts can effectively achieve hydrogen evolution in alkaline conditions, among which the H2O dissociation energy barriers of Cu(210)-Os and Cu(210)-Ru are just 0.47 eV and 0.60 eV, which are much lower than that of pure Pt(111). Thus, it is expected that Cu(210) doped with proper noble metal elements is an ultra-low-cost and ultra1-high-performance catalyst for alkaline HER. Meanwhile, Os and Ru-doped Cu(110) and Cu(211) surfaces also demonstrate remarkable alkaline HER activity compared with the metal catalysts that have been reported hitherto. These offer a novel concept and theoretical guidance to design cheaper and more efficient HER catalysts.

A self-reactivated PdCu catalyst for aldehyde electro-oxidation with anodic hydrogen production

The low-potential aldehyde oxidation reaction can occur at low potential (~0 VRHE) and release H2 at the anode, enabling hydrogen production with less than one-tenth of the energy consumption required for water splitting. Nevertheless, the activity and stability of Cu catalysts remain inadequate due to the oxidative deactivation of Cu-based materials. Herein, we elucidate the deactivation and reactivation cycle of Cu electrocatalyst and develop a self-reactivating PdCu catalyst that exhibits significantly enhanced stability. Initially, in-situ Raman spectroscopy confirm the cycle involved in electrochemical oxidation and non-electrochemical reduction. Subsequently, in-situ Raman spectroscopy and X-ray absorption fine structure reveal that the Pd component accelerates the rate of the non-electrochemical reduction, thereby enhancing the stability of the Cu-based electrocatalyst. Finally, a bipolar hydrogen production device is assembled utilizing the PdCu electrocatalyst, which can deliver a current of 400 mA cm−2 at 0.42 V and operate continuously for 120 h. This work offers guidance to enhance the stability of the Cu-based electrocatalyst in a bipolar hydrogen production system.

Size and Morphology Dependent Activity of Cu Clusters for CO2 Activation and Reduction: A First Principles Investigation.

Various Cu-based materials in diverse forms have been investigated as efficient catalysts for electrochemical reduction of CO2; however, they suffer from issues such as higher over potential and poor selectivity. The activity and selectivity of CO2 electro reduction have been shown to change significantly when the surface morphology (steps, kinks, and edges) of these catalysts is altered. In light of this, size and morphology dependent activity of selected copper clusters, Cun (n=2-20) have been evaluated for the activation and reduction of CO2 molecule. The phase-space of these copper clusters is rich in conformations of distinct morphologies starting from planar, 2D geometries to prolate-shaped geometries and also high-symmetry structures. The binding efficiency and the activation of CO2 are highest for medium sized clusters (n=9-17) with prolate-morphologies as compared to small or larger sized CunCO2 clusters that are existing mainly as planar (triangular, tetragonal etc.) or highly-symmetric geometries (icosahedron, capped-icosahedron etc.), respectively. The best performing (prolate-shaped) CunCO2 conformations are quite fluxional and also they are thermally stable, as demonstrated by the molecular dynamics simulations. Furthermore, on these CunCO2 conformations, the step-by-step hydrogenation pathways of CO2 to produce value-added products like methanol, formic acid, and methane are exceptionally favorable and energy-efficient.

Cu/Fe3O4 magnetic aerogel for the capture and immobilization of iodine anion from water

Effective radioactive-iodine-anion (I−) removal has garnered considerable research attention. Cu-based porous materials stand out among adsorbents because of their low toxicity and high cost-effectiveness. However, the low adsorption capacity and long equilibrium time of Cu-based adsorbents hinder their practical applications. Herein, we employed bimetallic co-gelation to prepare a Cu/Fe3O4 magnetic aerogel (Cu/Fe3O4-MA) with high reactivity for removing I− from water, achieving an I− adsorption capacity that surpassed those achieved in previous studies. Structural characterization results indicated that the Cu/Fe3O4-MA had highly dispersed Cu and abundant pores in its structure, providing good conditions for efficiently capturing I−. Batch experiments showed that the Cu/Fe3O4-MA had a high I− capacity (477.5 mg/g) and rapidly reached apparent adsorption equilibrium (<3 h). The adsorbent can effectively immobilize the adsorbed I− while maintaining stability even at elevated temperatures (up to 563 °C). Moreover, rapid recovery of the adsorbent could be achieved by applying a magnetic field, considerably improving recycling efficiency. This work demonstrates the considerable potential of the Cu/Fe3O4-MA in the rapid elimination of radioactive I−.

Role of electrons and H* in electrocatalytic nitrate reduction to ammonium for CuNi alloy

Electrocatalytic reduction of nitrate (NO3-) to ammonium (NH4+) is an environment friendly approach for treating nitrogen-containing wastewater. Consequently, electrocatalysts capable of effectively and selectively reducing NO3- to NH4+ receives growing attention. However, Cu-based catalysts demonstrate limited efficiency and the drawback of generating toxic NO2- though it is prevalent in the field of electrocatalytic reduction of NO3- (NO3RR). In this work, a CuNi alloy was synthesized on a Co foil through electrodeposition (marked as CuNi@Co) and its electrocatalytic performance for NO3RR was evaluated. XRD, EDS mapping and XPS characterization indicate CuNi exists with alloy state. Electrocatalytic experiments demonstrate that CuNi@Co exhibits an exceptional FENH3 of 99.12% at -0.64 V (vs. RHE). Importantly, no detrimental NO2- generated during NO3RR process because the reduction rate from NO2- to NH4+ is faster than that from NO3- to NO2-. Mechanistic analysis suggests that Cu serves as a ‘reservoir’ to provide electrons to facilitate the reduction of NO3- to NO2- during NO3RR process and the synergistic effect of Ni and Cu promotes more active hydrogen (H*) to participate the reduction process of NO2- to NH4+ not H2 generation, ultimately improving FENH3. This work elucidates the role of electrons and H* in electrocatalytic nitrate reduction to ammonium for CuNi alloy, providing new insights into the reduction process of NO3RR for Cu-based materials.

Stimulating the C−C coupling ability of ultrafine copper nanoclusters via nitrogen coordination for electrocatalytic CO2 reduction

Cu-based materials are widely regarded as the most effective electrocatalysts for selectively reducing CO2 to multi-carbon products. Nevertheless, the ultrafine Cu nanoclusters are generally inefficient in electro-reducing CO2 to multi-carbon products because of their exceptionally high d-band center, which leads to binding with the CO intermediates strongly and impeding the C−C coupling. Herein, we report that a nitrogen coordination strategy can significantly stimulate the ultrafine copper nanoclusters’ C−C coupling ability. Strikingly, the Faradaic efficiency (FE) of CO2-to-C2H4 over the N-coordinated Cu nanoclusters on nitrogen-modified carbon support (Cu-N/NC) is up to 61.4 % with a current density of −208 mA cm−2 at −1.05 V (vs RHE), which is much superior to the pure copper nanoclusters/nanoparticles (FE(C2H4)＜5 %). Theoretical calculations unveil that the N coordination can optimize the d-band center of copper clusters and its adsorption energy toward *CO, which largely reduces the energy barrier of the C−C coupling step (from 1.28 eV to 0.35 eV) and thus improves the C2H4 selectivity. In-situ Raman spectra and CO-TPD tests prove that the Cu-N/NC catalyst exhibits the best CO adsorption strength to benefit C−C coupling. Moreover, the CO2 reduction current density of the Cu-N/NC catalyst remains stable at about 210 mA cm−2 with the FE(C2H4) remaining at about 60 % during a 12-hour durability test, showing excellent catalytic stability.

Efficient degradation of norfloxacin by synergistic activation of PMS with a three-dimensional electrocatalytic system based on Cu-MOF

In this work, Cu-based metal-organic framework material (Cu-MOF) was combined with an electric field to construct a three-dimensional electrocatalytic synergistic activation of peroxymonosulfate sulfate (PMS) system (3D/Cu-MOF/EC/PMS) for the degradation of norfloxacin (NOR). The results show that the synergistic degradation efficiency of the Cu-MOF material with the electric field is enhanced by nearly 64 % relative to the degradation efficiency of the two alone. The quenching experimental and EPR characterization indicates that ROS plays an important role in the degradation process, with O2– playing a dominant role. Finally, the degradation pathway of NOR was explored by DFT study and LC-MS tests, and the toxicity evaluation software (TEST) and CCK-8 cytotoxicity experimental studies demonstrated that the sewage after the degradation of NOR by this system would have little or no effect on human liver cells (L02). This study not only shows that the 3D/Cu-MOF/EC/PMS system can treat the water containing higher concentrations of NOR into a state that is not harmful to the human body but also provides a new idea for the improvement of catalysts that do not have obvious catalytic degradation effects.

Overview on aluminium alloys as sinks for end-of-life vehicle scrap

Abstract A fundamental principle in metallurgy is that the higher the purity of metals and alloys, the more favourable their properties will be. However, as the recycling of materials in production becomes increasingly significant, the levels of impurities are also on the rise. In the case of aluminium, the consequences can be detrimental due to the low solubility of most elements in this metal, which leads to the formation of brittle intermetallic phases (IMPs). Moreover, once impurities have entered aluminium, it is difficult to remove them. In 2017, almost 100 million cars were produced worldwide. Historically, vehicle design prioritised performance, resulting in a multi-material mix to utilise the best materials for each application. This included over 40 different wrought and cast aluminium alloys, Cu-based materials for electrics, and steels for high-strength applications. In the recycling of end-of-life vehicles (ELVs), high purity wrought Al alloys are today down-cycled to low purity cast engine blocks. However, recent advancements show that the drawback of increase IMP-fractions can be turned into benefits through the strategic design of heterostructured alloys. A first successful alloy example from this approach enables interesting forming properties, previously only found in 5xxx series wrought aluminium alloys, in combination with a matrix composition and age-hardening potential known from 6xxx series wrought aluminium alloys. A second examples reviews compositions directly resulting from ELV scrap. By manipulating IMPs it is feasible to create heterostructures with an interesting balance of strength and ductility. These approaches challenge traditional views, allowing for a greater volume fraction of intermetallic phases. Understanding the formation and role of intermetallic particles is crucial. This work gives an overview to the current problem and the state of the art and addressed the potential of upcycled aluminium alloys that tolerate high impurity levels by using intermetallic phases as impurity sinks.

Synergistic reinforcement mechanisms of Cu/graphite composites with MAX phase Ti2AlN and ZrO2-B4C ceramics: Enhancements in mechanical, thermal, and tribological properties

In braking materials field, MAX phase has been introduced into Cu-based composite materials to address issues such as inadequate wetting between ceramic particles and the metal matrix. This study focuses on preparing Ti2AlN-ZrO2-B4C reinforced Cu-based materials via the powder metallurgy method, and investigates the effects and mechanisms of different Ti2AlN/ZrO2 ratios on the mechanical, thermal, and tribological properties of these materials. The addition of an appropriate amount of Ti2AlN (3 wt%) can enhance the densification and mechanical properties of Cu-based materials, as the diffusion of Al atoms promotes the sintering process. Similarly, the diffusion of Al also improves the thermal conductivity at grain boundaries, resulting in samples with higher Ti2AlN content exhibiting superior thermal diffusivity. When the Ti2AlN content reached 7 wt%, the material exhibited optimal hardness (43.35 ± 1.05 HBW), moderate shear strength (19.84 ± 1.86 MPa), as well as excellent high initial braking speed friction coefficient and stability. The reinforcement primarily arises from the diffusion bonding between Ti2AlN and Cu, leading to the formation of Cu-Ti compounds at the interface, which facilitates Ti2AlN in providing frictional force during the friction process and promotes the formation of a friction film due to the “pinning effect”. Additionally, the layered structure of Ti2AlN and the subsequent formation of amorphous Al2O3 after oxidation contributed to the enhancement of friction stability.

Mg-Doped Cu Catalyst for Electroreduction of CO2 to Multicarbon Products: Lewis Acid Sites Simultaneously Promote *CO Adsorption and Water Dissociation.

The electroreduction of CO2 to valuable fuels or high-value chemicals by using sustainable electric energy provides a promising strategy for solving environmental problems dominated by the greenhouse effect. Copper-based materials are the only catalysts that can convert CO2 into multicarbon products, but they are plagued by high potential, low selectivity, and poor stability. The key factors to optimize the conversion of CO2 into multicarbon products are to improve the adsorption capacity of intermediates on the catalyst surface, accelerate the hydrogenation step, and improve the C-C coupling efficiency. Herein, we successfully doped Lewis acid Mg into Cu-based materials using a simple liquid-phase chemical method. In situ Raman and FT-IR tracking show that the Mg site enhances the surface coverage of the *CO intermediate, simultaneously promoting water dissociation. Under an industrial current density of 0.7 A cm-2, the FEC2+ reaches 73.9 ± 3.48% with remarkable stability. Density functional theory studies show that doping the Lewis acid Mg site increases the coverage of *CO and accelerates the splitting of water, thus promoting the C-C coupling efficiency, reducing the reaction energy barrier, and greatly improving the selectivity of C2+ products.

Fabrication of a family of BiOI-doped copper-organic frameworks for enhancing photocatalytic degradation of dyes

Organic dyes are one of the most popular dyes used in industrial and consumption nowadays, and the use of dyes has certain hazards. One of the greenest and most efficient methods for breaking down organic contaminants is photocatalysis. It is a green technology that has enormous promise for the environment and energy sectors. In this work, p-type BiOI nanosheets were deposited in situ on n-type copper-based metal–organic framework (Cu-MOF) to create a unique BiOI@Cu-MOF heterojunction. The BiOI@Cu-5 heterojunction that is optimized showed nearly 100 % removal of rose Bengal (RB) under UV irradiation as well as the degradation rates of methyl orange (MO), crystal violet (GV), methylene blue (MB), and rhodamine B (RhB) were 99.70 %, 95.70 %, 27.20 %, and 23.90 %, respectively. First, the introduction of narrow bandgap BiOI into the material can effectively enhance its absorption of sunlight. Secondly, the high specific surface of the Cu-based MOFs material is favorable for improving the catalytic activity of the catalyst. More critically, the intrinsic electric field at the Cu-MOFs/BiOI heterojunction interface facilitates a successful division of photogenerated electron-hole pairs. Further studies revealed that the photogenerated holes are the important active ingredients for RB scavenging. In this paper, Bi-based semiconductors were used to create p-n heterostructures that will bring new ideas for increasing MOF photocatalytic activity.

Evaluation of mechanical and tribological properties of Cu-based friction materials reinforced by 3D mesh structure

Cu-based friction materials (CBFMs) are widely used in brake system such as High-Speed Trains and Wind Power Generation, its mechanical and tribological properties are of vital importance for the stable and safe operation. In this study, CBFMs holding 3D mesh structure were designed and fabricated by wet granulation and particle coating technology. Stress and temperature fields were obtained by finite element simulation. After that, the mechanical and tribological properties were investigated. The results showed that 3D mesh structure can enhance the compressive strength of CBFMs to 34.56 % and reduce wear rate to a large extent. This study was expected to open up a new direction in enhancing comprehensive performances of CBFMs without changing its composition.

Cu-based composite materials derived from MOFs for visible light PMS activation in tetracycline removal

The degradation of recalcitrant antibiotics through the activation of peroxymonosulfate (PMS) is an important branch of advanced oxidation processes (AOPs), with widespread attention given to the application of metal-organic frameworks (MOFs) in this field. The article successfully synthesized CuxO/N-doped carbon/Cu-MOF (CuxO/NC/Cu-MOF) nanocomposites by low-temperature thermal treatment of Cu-MOF precursors. Compared with the original MOF, these partially decomposed composite materials exhibit significantly stronger catalytic activity towards PMS, efficiently removing organic pollutants such as tetracycline (TC). After optimization, the sample treated at 400 °C, under visible light with PMS assistance, achieves an impressive degradation rate, almost completely degrading a 50 mL TC solution (10 mg/L) after 80 min. This achievement surpasses the degradation rate observed with the original Cu-MOF by 2.1 times. In the composite system of CuxO/NC/Cu-MOF+PMS+Vis, the significant enhancement of activity is credited to the effective spatial separation of photogenerated electrons and holes, as well as the utilization of 1O2 as the primary active oxygen species. This work provides a simple preparation strategy for the development of Cu-based PMS activators with excellent photocatalytic performance.

Noble metal-modified copper surfaces for alkaline condition hydrogen evolution reaction

Cu-based materials would be attractive candidates for cost-effective alkaline hydrogen evolution reaction (HER) electrocatalysts due to high abundance, excellent conductivity, and excellent stability in alkaline environments, if not for the inherent inertness of Cu in HER. This inertness has led to a relative lack of research on Cu-based HER catalysts in both experimental and theoretical domains. Here, We report engineered Cu(111) surfaces that can significantly improve the poor activity of H2O dissociation on pure Cu(111) surface. We do this by introducing noble metal atoms (M = Ru, Rh, Pd, Ag, Os, Ir, Pt) through surface doping. These modified surfaces exhibit excellent thermodynamic and electrochemical stability, with the exception of Cu(111)-Ag. Notably, the H2O dissociation energy barrier on Cu(111)-Os (Eb) is only 0.74 eV, which is much smaller than that (1.31 eV) of pure Cu(111), and is even lower than that of Pt (Eb = 0.92 eV), which is commercially used for electrodes. The low Eb and resulting expected excellent performance of Cu(111)-Os for water splitting is related to the particular local electronic properties of doped Os atoms, specifically the electronic structure of the Os d-orbitals, which have a d-band center near Fermi level (EF) and a high density of states around EF, including just above EF. These results are expected to stimulate the investigation of surface alloyed Cu, leading to a new direction for the design of high-performance and low-cost electrocatalysts.

Design and optimization of (FA)2BiCuI6-based double perovskite solar cells using kesterite CBTS as hole transport layer for high power conversion and quantum efficiency

This work introduces the design of a novel architecture for double perovskite solar cells (DPSCs) utilizing (FA)2BiCuI6, known for its enhanced stability relative to single perovskite materials for production of efficient, ultra-thin solar cells. The proposed architecture features a unique device configuration of ITO/WO3/(FA)2BiCuI6/Cu2BaSnS4/W, incorporating a Kesterite type Cu-based quaternary chalcogenide material, Cu2BaSnS4 known as CBTS, is used as hole transport layer (HTL) with a bandgap of 1.9 eV, WO3 as the electron transport layer (ETL) with a 2.6 eV bandgap, and (FA)2BiCuI6 as the absorber layer with a 1.55 eV bandgap. The study provides an in-depth theoretical analysis of the energy band structure, defects, and quantum efficiency of the DPSC, highlighting the device’s post-optimization photovoltaic parameters. Remarkably, the optimized DPSC demonstrated superior performance with a PCE of 24.63%, Voc of 1.16 V, Jsc of 25.67 mA cm−2, and FF of 82.87%. The research also explores the effects of various factors on photovoltaic performance, including temperature, interface defect, and generation and recombination rates, as well as work function of back contact materials. The results underscore the exceptional potential of (FA)2BiCuI6, especially when combined with the HTL CBTS, in significantly reducing sheet resistance and enhancing the overall performance of solar cells. The design is validated using the SCAPS-1D simulation software tool.

(Invited) In Situ Study of Catalyst Structural Evolution during CO2 Electroreduction by Development of Electrochemical Liquid Cell TEM

The electrocatalytic CO2 reduction reaction (CO2RR) has attracted significant interest of study in the exploration of sustainable energy and environment. Cu-based materials have demonstrated the capability of converting CO2 to multi-carbon products with high catalytic activity and low cost. Since the performance of heterogenous catalysts is highly susceptible to the catalyst structural changes, unveiling the structure and catalytic active sites during reactions is crucial to the understanding of catalytic mechanisms. Although lots of efforts have been made, it remains a challenge to directly image the atomic structure of a working catalyst in liquid electrolytes due to technical difficulties. Here, I will show our development of in-situ electrochemical liquid cell transmission electron microscopy (TEM) for the study of Cu catalysts during electrocatalytic CO2RR. The novel electrochemical liquid cell allows unprecedented atomic imaging of the catalyst evolution during electrochemical reactions. Our observations reveal that the Cu catalyst-electrolyte interaction under an applied potential (-1.1 v) leads to structural changes of Cu catalyst surfaces. Intermediate structure dynamics have been captured. The propagations and transformations of intermediates result in atomically rough Cu crystal surfaces. The intermediates are further found mediating the mass loss of Cu. Control experiments demonstrate the intermediates can be utilized for enhanced carbon-carbon coupling and the formation of two carbon products. Insights gained from this study are not only valuable to designing novel catalysts, but also useful for understanding of electrified solid-liquid interfaces in general.

Electrocatalytic Synthesis of Urea

Many industrial chemical processes involve a high-energy demand (often still derived from fossil fuels). Urea is an important chemical for the agricultural industry, which accounts for 70% of the global nitrogen-containing fertilizer usage. Currently, urea is produced by the reaction of liquid NH3 and CO2 [1] in a process known as the Haber-Meiser process. Despite its importance, this process suffers from high energy demand and CO2 emissions, mainly due to the NH3 synthesis step (Haber- Bosch process), which relies on fossil fuel resources. Making urea with electrochemical methods has recently gained interest from the scientific community as this approach provides a way to reduce the high CO2 emissions currently associated with urea production. Among the various nitrogen sources explored for urea electrosynthesis, nitrate (NO3-) is attractive because of its high solubility in water, low dissociation energy and potential to mitigate NO3 − contaminations in water. Even though the mechanism of urea synthesis via CO2 and NO3 - coupling is still controversial and not broadly studied, most reports implicate CO* and NH2* surface intermediates in urea synthesis.[2] Cu is an attractive electrocatalyst as it can reduce CO2 to CO and further products and it is also an active catalyst for the reduction of nitrate to ammonia Previous reports on Cu and Cu-based materials showed that urea can be obtained from NO2 -.[3,4] Early research by Shibata et al. with various catalysts demonstrated that the highest faradaic efficiency towards urea from NO3 - was achieved with a Zn catalyst.[5] In this presentation, I will show our latest results on the development of Cu bimetallic catalysts ( CuRh) for urea electrosysnthesis from CO2 and NO3 -[6,7].

Critical Review of Cu-Based Hole Transport Materials for Perovskite Solar Cells: From Theoretical Insights to Experimental Validation.

Despite the remarkable efficiency of perovskite solar cells (PSCs), long-term stability remains the primary barrier to their commercialization. The prospect of enhancing stability by substituting organic transport layers with suitable inorganic compounds, particularly Cu-based inorganic hole-transport materials (HTMs), holds promise due to their high valence band maximum (VBM) aligning with perovskite characteristics. This review assesses the advantages and disadvantages of these five types of Cu-based HTMs. Although Cu-based binary oxides and chalcogenides face narrow bandgap issues, the "chemical modulation of the valence band" (CMVB) strategy has successfully broadened the bandgap for Cu-based ternary oxides and chalcogenides. However, Cu-based ternary oxides encounter challenges with low mobility, and Cu-based ternary chalcogenides face mismatches in VBM alignment with perovskites. Cu-based binary halides, especially CuI, exhibit excellent properties such as wider bandgap, high mobility, and defect tolerance, but their stability remains a concern. These limitations of single anion compounds are insightfully discussed, offering solutions from the perspective of practical application. Future research can focus on Cu-based composite anion compounds, which merge the advantages of single anion compounds. Additionally, mixed-cation chalcogenides such as CuxM1-xS enable the customization of HTM properties by selecting and adjusting the proportions of cation M.

Toward Developing Superior Cu-Based Metal-Organic Framework-Derived Materials for Electrocatalytic Oxidation of Ethanol.

This project addresses the urgent need for efficient and cost-effective development of electrocatalysts for the ethanol oxidation reaction (EOR). This reaction offers promising renewable energy solutions but faces challenges due to the slow EOR kinetics, typically requiring costly noble metal catalysts. To overcome these limitations, this study focuses on developing CuZn-based EOR catalysts derived from metal-organic frameworks (MOFs), focusing on understanding the structure-performance relationship between pristine MOF-based electrocatalysts and their pyrolyzed counterparts. Herein, bimetallic MOF materials with varying Cu/Zn ratios were synthesized, followed by pyrolysis to produce carbonized counterparts while preserving the fundamental structure but with altered physicochemical properties. Comparative EOR studies revealed the superior performance of pyrolyzed MOFs, demonstrating that optimized Zn-loading is crucial over Cu-based framework for catalyst performance and durability. Overall, this work highlights the potential of MOF-derived Cu-based catalysts for renewable energy applications and provides insights into optimizing their performance through controlled synthesis and post-treatment strategies.