24 KJEMI 1 2025 Song Lu With rapid development of the global economy, energy crisis and environment issues have become increasingly prominent. Carbon dioxide (CO₂) is a primary greenhouse gas (GHG), while it could also be a valuable carbon source (Figure 1). Electrochemical CO₂ reduction (ECR) to valuable fuels and chemicals, potentially powered by renewable electricity sources, has received extensive attention in recent years by both academia and industry. ECR can convert CO₂ to value-added products such as C1 (e.g., CO, HCOOH, CH₄), C₂ (e.g., C₂H₄, C₂H₅OH), and C₃ (e.g., C₃H₇OH) under ambient temperature and pressure. Nevertheless, CO₂ is an inert and stable molecular, and its activation and chemical conversion still has some challenges in terms of the development and commercialization of the electrocatalysts: they still suffer from sluggish kinetics, poor product selectivity, catalyst deactivation, and high overpotential. The focus of my PhD research is to design and develop efficient electrocatalysts for CO₂ reduction to valuable fuels or chemicals, i.e., in the field of CO₂ conversion and utilization (CCU). The research firstly focused on metal nanoparticles as electrocatalysts for ECR, but moved to more advanced single atom catalysts (SACs) and dual atom catalysts (DACs), which showed significant improvement in CO₂ conversions. We fabricated silver (Ag) nanoparticles (NP) loaded on boron-doped g-C₃N₄ (Ag-B-g-C₃N₄) nanocomposite that achieved impressive performance in converting CO₂ to CO, showing a total current density of 2.08 mA cm–² and a CO Faradaic efficiency of 93.2% under the potential of −0.8 V. SACs with single atom as active center are of great interest due to maximum atom utilization and excellent performance. Our research indicated that some metal atoms, like vanadium and nickel, embedded in specific materials, could effectively convert CO₂. By tuning the chemical environment of these single metal atoms, e.g., adding sulfur and nitrogen into carbon substrate, we developed sulfur decorated Ni single-atom catalysts that achieved almost 100% efficiency in converting CO₂ to CO! And it was stable for over 19 hours, which is a big deal in this field. Constructing heteronuclear dimer sites to form dual-atom catalysts is another efficient way to tune the coordination environment and the electronic properties of the active centers of SACs (Figure 2). In DACs, two different metal atoms work together to improve the ECR performance for CO₂ conversion. Our Mn-Ni dual-atom catalyst, for example, reached nearly 99% efficiency for converting CO₂ to CO with impressive current density and stability. For the first protonation process, Mn and Ni atoms act together to accelerate *COOH formation. However, during *CO desorption process, only Ni atom bonds with C atom of *CO, promoting *CO desorption. Therefore, superior performance for the Mn−Ni−NC catalyst in ECR to CO was achieved. Transition-metal-mediated electrocatalytic CO₂ reduction: from nanoparticles to single-atom catalysts Figure 1: CO₂ reduction to various value-added fuels and chemicals through renewable electricity and electrocatalysis.
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