Selective electrochemical reduction of CO2 on compositionally variant bimetallic Cu-Zn electrocatalysts derived from scrap brass alloys

Multi-Site CuZn Alloy Boosts Nitrate Reduction to Ammonia via Optimized Intermediate Adsorption

Electrocatalytic nitrate reduction reaction (NO3RR) is an effective way to solve nitrate pollution and a promising strategy for ammonia (NH3) synthesis under ambient temperature and pressure. However, NO3RR is still hindered by the lack of efficient catalysts and an understanding of mechanisms that enhance the catalytic performance. In this study, we propose intermetallic alloying as a promising strategy to optimize the NO3RR reaction pathway by tuning the adsorption energies and configurations of intermediates, as demonstrated by density functional theory (DFT) calculations comparing NO3RR performance of Cu (111) and CuZn (110) surfaces. In CuZn alloy, the electron-donating property of Cu weakens the adsorption of NOx (x = 1, 2, and 3) intermediates, whereas the electron-accepting property of Zn strengthens the binding of NOxH intermediates, thus lowering the protonation reaction energy. Zn sites preferentially promote the removal of O species, whereas Cu sites dominate the protonation of N species. This synergistic effect enables CuZn (110) surface to successfully break the undesirable scaling relationship in traditional metal catalysts, resulting in excellent catalytic activity for NO3RR, with an ultra-low limiting potential of -0.28 V. This work provides valuable insights and theoretical guidance for NO3RR.

Recent insights on the use of modified Zn-based catalysts in eCO2RR

Converting CO2 into valuable chemicals can provide a new path to mitigate the greenhouse effect, achieving the aim of "carbon neutrality" and "carbon peaking". Among numerous electrocatalysts, Zn-based materials are widely distributed and cheap, making them one of the most promising electrocatalyst materials to replace noble metal catalysts. Moreover, the Zn metal itself has a certain selectivity for CO. After appropriate modification, such as oxide derivatization, structural reorganization, reconstruction of the surfaces, heteroatom doping, and so on, the Zn-based electrocatalysts can expose more active sites and adjust the d-band center or electronic structure, and the FE and stability of them can be effectively improved, and they can even convert CO2 to multi-carbon products. This review aims to systematically describe the latest progresses of modified Zn-based electrocatalyst materials (including organic and inorganic materials) in the electrocatalytic carbon dioxide reduction reaction (eCO2RR). The applications of modified Zn-based catalysts in improving product selectivity, increasing current density and reducing the overpotential of the eCO2RR are reviewed. Moreover, this review describes the reasonable selection and good structural design of Zn-based catalysts, presents the characteristics of various modified zinc-based catalysts, and reveals the related catalytic mechanisms for the first time. Finally, the current status and development prospects of modified Zn-based catalysts in eCO2RR are summarized and discussed.

Cu and Zn promoted Al-fumarate metal organic frameworks for electrocatalytic CO2 reduction

Metal organic frameworks (MOFs) are attractive materials to generate multifunctional catalysts for the electrocatalytic reduction of CO2 to hydrocarbons. Here we report the synthesis of Cu and Zn modified Al-fumarate (Al-fum) MOFs, in which Zn promotes the selective reduction of CO2 to CO and Cu promotes CO reduction to oxygenates and hydrocarbons in an electrocatalytic cascade. Cu and Zn nanoparticles (NPs) were introduced to the Al-fum MOF by a double solvent method to promote in-pore metal deposition, and the resulting reduced Cu-Zn@Al-fum drop-cast on a hydrophobic gas diffusion electrode for electrochemical study. Cu-Zn@Al-fum is active for CO2 electroreduction, with the Cu and Zn loading influencing the product yields. The highest faradaic efficiency (FE) of 62% is achieved at -1.0 V vs. RHE for the conversion of CO2 into CO, HCOOH, CH4, C2H4 and C2H5OH, with a FE of 28% to CH4, C2H4 and C2H5OH at pH 6.8. Al-fum MOF is a chemically robust matrix to disperse Cu and Zn NPs, improving electrocatalyst lifetime during CO2 reduction by minimizing transition metal aggregation during electrode operation.

Metallic 1T-N-WS2 /WO3 Heterojunctions Featuring Interface-Engineered Cu-S Configuration for Selective Electrochemical CO2 Reduction Reaction

Electrocatalytic carbon-dioxide reduction reactions (ECO2 RR) are one of the most rational techniques to control one's carbon footprint. The desired product formation depends on deliberate reaction kinetics and a choice of electron-proton contribution. Herein the usage of novel CuS active centers decorated over stable 1T metallic N-WS2 /WO3 nanohybrids as an efficient selective formate conversion electrocatalyst with regard to ECO2 RR is reported. The preferred reaction pathway is identified as *OCHO, which is reduced (by gaining H+  + e- ) to HCOO- (HCOO- path) as the primary product. More significantly, at -1.3 V versus RHE yield of FEHCOO - is 55.6% ± 0.5 with a Jgeo of -125.05 mA cm-2 for CuS@1T-N-WS2 /WO3 nanohybrids. In addition, predominant catalytic activity, selectivity, and stability properties are observed; further post-mortem analysis demonstrates the choice of material importance. The present work describes an impressive approach to develop highly active electrocatalysts for selective ECO2 RR applications.

Bridging Trans-Scale Electrode Engineering for Mass CO2 Electrolysis

Electrochemical CO2 upgrade offers an artificial route for carbon recycling and neutralization, while its widespread implementation relies heavily on the simultaneous enhancement of mass transfer and reaction kinetics to achieve industrial conversion rates. Nevertheless, such a multiscale challenge calls for trans-scale electrode engineering. Herein, three scales are highlighted to disclose the key factors of CO2 electrolysis, including triple-phase boundaries, reaction microenvironment, and catalytic surface coordination. Furthermore, the advanced types of electrolyzers with various electrode design strategies are surveyed and compared to guide the system architectures for continuous conversion. We further offer an outlook on challenges and opportunities for the grand-scale application of CO2 electrolysis. Hence, this comprehensive Perspective bridges the gaps between electrode research and CO2 electrolysis practices. It contributes to facilitating the mixed reaction and mass transfer process, ultimately enabling the on-site recycling of CO2 emissions from industrial plants and achieving net negative emissions.

Fabrication of polyhedral Cu-Zn oxide nanoparticles by dealloying and anodic oxidation of German silver alloy for photoelectrochemical water splitting

A significant effort has been dedicated to the synthesis of Cu-Zn oxide nanoparticles as a robust photocathode material for photoelectrochemical water splitting. Cu-Zn oxide nanoparticles were formed by controlled anodization of German silver (Cu-Zn-Ni) alloy in an aqueous electrolyte. Scanning electron microscopy (SEM) demonstrates the dependence of the obtained nanostructures on the anodization time. The X-ray diffraction (XRD) patterns showed the formation of copper oxide (CuO) and zinc oxide (ZnO) nanoparticles with good stability. This was also confirmed by the compositional X-ray photoelectron spectroscopy (XPS) analysis. The obtained polyhedral nanoparticles showed high optical activity with adequate bandgap energy. These optimized nanoparticles achieved boosted photocurrent of - 0.55 mA/cm2 at - 0.6 V vs. SCE under AM 1.5 illumination, confirming the role of the optimized dealloying and thermal treatment in tuning the photoelectrochemical performance of the material.