This review discusses the electrochemical reduction of carbon dioxide (ECO₂RR), a promising method for converting waste into valuable materials while reducing carbon emissions and producing clean energy. The study first introduces the mechanisms of ECO₂RR based on the number of carbon atoms in the products. It then reviews the structural-activity relationships of electrocatalysts, classifying the latest developments in various types of advanced electrocatalysts, including atomically-dispersed catalysts, alloys, metal-organic frameworks (MOFs), and covalent organic frameworks (COFs). Theoretical insights are provided on different aspects of the reaction, and challenges are discussed from both materials and device perspectives to inspire further research for industrial application. The ECO₂RR process faces challenges due to the high activation energy barrier and competition with the hydrogen evolution reaction (HER). Efficient catalysts are needed to overcome these challenges, as current catalysts often have high overpotential and low selectivity. The reaction involves multielectron transfer processes, leading to complex product mixtures, making separation and purification difficult. Understanding the reaction mechanism and intermediates is crucial for catalyst design and modification. Theoretical calculations and modeling provide insights into binding energy, free energy, and activation energy of intermediates, helping evaluate the feasibility of reaction steps and identify key intermediates. Experimental studies show that different catalysts produce various products, such as CO, formate, methane, and ethanol, depending on conditions. The electrochemical reduction of CO₂ involves multiple steps, with the formation of HCOOH, CO, HCHO, CH₃OH, CH₄, C₂H₄, CH₃CH₂OH, and CH₃CH₂CH₂OH being key processes. The electronic structure of catalysts is crucial for optimizing catalytic performance, affecting activity, selectivity, and stability. Metal centers play a key role in adsorbing CO₂ and activating it into different products. Single-atom catalysts (SACs) of various metals, such as Mo, Fe, Co, Ni, Cu, Zn, Au, Ag, Pt, Ir, Bi, Sn, and Sb, have been studied for their intrinsic electrocatalytic properties. The structure of the catalyst, including metal sites, vacancy defects, and coordination environments, significantly influences the reaction pathway and product selectivity. Vacancy defects, such as oxygen (V_O) and anion vacancies, enhance catalytic performance by modifying the electronic structure and providing additional active sites. Cationic vacancies also play a role in regulating the electronic structure and improving catalytic activity. Strain engineering, which modifies the d-band center position, can enhance the reaction rate and selectivity by altering the binding energy barrier. Coordination environments, such as N-doped M-N-C structures, are crucial for regulating the electrocatalytic performance, with different configurations showing varying levels of activity. The review highlights the importance of understanding the structureThis review discusses the electrochemical reduction of carbon dioxide (ECO₂RR), a promising method for converting waste into valuable materials while reducing carbon emissions and producing clean energy. The study first introduces the mechanisms of ECO₂RR based on the number of carbon atoms in the products. It then reviews the structural-activity relationships of electrocatalysts, classifying the latest developments in various types of advanced electrocatalysts, including atomically-dispersed catalysts, alloys, metal-organic frameworks (MOFs), and covalent organic frameworks (COFs). Theoretical insights are provided on different aspects of the reaction, and challenges are discussed from both materials and device perspectives to inspire further research for industrial application. The ECO₂RR process faces challenges due to the high activation energy barrier and competition with the hydrogen evolution reaction (HER). Efficient catalysts are needed to overcome these challenges, as current catalysts often have high overpotential and low selectivity. The reaction involves multielectron transfer processes, leading to complex product mixtures, making separation and purification difficult. Understanding the reaction mechanism and intermediates is crucial for catalyst design and modification. Theoretical calculations and modeling provide insights into binding energy, free energy, and activation energy of intermediates, helping evaluate the feasibility of reaction steps and identify key intermediates. Experimental studies show that different catalysts produce various products, such as CO, formate, methane, and ethanol, depending on conditions. The electrochemical reduction of CO₂ involves multiple steps, with the formation of HCOOH, CO, HCHO, CH₃OH, CH₄, C₂H₄, CH₃CH₂OH, and CH₃CH₂CH₂OH being key processes. The electronic structure of catalysts is crucial for optimizing catalytic performance, affecting activity, selectivity, and stability. Metal centers play a key role in adsorbing CO₂ and activating it into different products. Single-atom catalysts (SACs) of various metals, such as Mo, Fe, Co, Ni, Cu, Zn, Au, Ag, Pt, Ir, Bi, Sn, and Sb, have been studied for their intrinsic electrocatalytic properties. The structure of the catalyst, including metal sites, vacancy defects, and coordination environments, significantly influences the reaction pathway and product selectivity. Vacancy defects, such as oxygen (V_O) and anion vacancies, enhance catalytic performance by modifying the electronic structure and providing additional active sites. Cationic vacancies also play a role in regulating the electronic structure and improving catalytic activity. Strain engineering, which modifies the d-band center position, can enhance the reaction rate and selectivity by altering the binding energy barrier. Coordination environments, such as N-doped M-N-C structures, are crucial for regulating the electrocatalytic performance, with different configurations showing varying levels of activity. The review highlights the importance of understanding the structure