An electrochemical cell with engineered indium oxide surfaces for efficient and selective carbon dioxide reduction to formate

Background

The electrochemical reduction of carbon dioxide (CO₂) has emerged as a promising approach for addressing both climate change and the growing demand for sustainable chemical feedstocks. By converting CO₂—a major greenhouse gas—into value-added products such as formate, this technology offers a pathway to close the carbon cycle and produce renewable fuels or industrial chemicals. The field has attracted significant attention due to the urgent need to mitigate atmospheric CO₂ levels and develop alternatives to fossil-derived chemicals. Electrochemical methods are particularly attractive because they can be powered by renewable electricity, potentially enabling decentralized and carbon-neutral production systems.

Despite this promise, current approaches to electrochemical CO₂ reduction face several significant challenges. Many existing electrode materials suffer from low selectivity, poor efficiency, and high energy requirements, often favoring the competing reduction of water to hydrogen gas over the desired CO₂ conversion. Traditional metal electrodes, such as unmodified indium or other metals, typically require high overpotentials to drive the reaction and yield only modest efficiencies for formate production. Furthermore, these systems often lack stability and can degrade under operational conditions, while the formation of unwanted byproducts further limits their practical application. As a result, there is a critical need for new electrode materials and surface treatments that can enhance both the efficiency and selectivity of CO₂ reduction, while operating at lower energy costs and maintaining long-term stability.

Technology

This technology centers on an electrochemical cell that employs an indium working electrode, which is deliberately modified to possess a surface layer of indium oxide and hydroxide. The modification is achieved through anodization in an alkaline solution, such as 1M potassium hydroxide, resulting in a rough, nanoparticulate surface with particle sizes between 20 and 100 nanometers. This engineered surface significantly increases the electrode’s active area and the number of catalytic sites, thereby lowering the overpotential required for the reduction of carbon dioxide (CO₂) to formate salts to approximately 900 mV. The process not only enhances the Faradaic efficiency for formate production—reaching up to 70%—but also suppresses the competing reduction of water to hydrogen gas, improving the selectivity and operational stability of the system. Comprehensive characterization (SEM, XPS, ATR-IR, XRD) confirms the formation and persistence of the oxide/hydroxide phases, which are critical for the observed catalytic performance.

What differentiates this technology is its purposeful and controlled surface engineering of the indium electrode, which directly addresses the limitations of conventional CO₂ electroreduction systems—namely, low efficiency, high overpotentials, and poor selectivity. Unlike untreated or acid-etched indium electrodes, the anodized, oxide-rich surface provides a dramatic increase in catalytic activity and selectivity for formate production, while effectively suppressing unwanted hydrogen evolution. The approach is simple, scalable, and robust, making it practical for real-world CO₂ conversion devices. Mechanistically, the nanostructured oxide/hydroxide interface not only increases the density of active sites but also creates a favorable electronic environment for CO₂ adsorption and activation, aligning with recent advances in heterogeneous catalysis. This positions the technology as a promising solution for sustainable fuel and chemical production, contributing to carbon-neutral energy systems.

Benefits

• Significantly enhanced Faradaic efficiency for CO₂ reduction to formate, reaching up to 70%
• Lower overpotential requirement (~900 mV), reducing energy consumption
• Suppression of competing hydrogen evolution, improving selectivity for formate
• Increased electrode surface area and active sites due to nanoparticulate indium oxide/hydroxide layer
• Improved stability and robustness of the electrochemical process
• Simple and scalable electrode surface treatment via anodization in alkaline solution
• Potential contribution to sustainable, carbon-neutral fuel and chemical production

Applications

• Industrial CO₂-to-formate conversion plants
• On-site chemical feedstock generation
• Renewable energy storage systems
• Carbon capture and utilization units

Additional info

This electrochemical system employs an indium working electrode featuring a nanoparticulate oxide/hydroxide surface layer generated through alkaline anodization. This modification produces 20–100 nm particles, significantly increasing active sites and surface area. It facilitates carbon dioxide reduction to formate with Faradaic efficiencies reaching 70% at reduced overpotentials (~900 mV). Crucially, the oxide layer suppresses competing hydrogen evolution, optimizing selectivity and stability for efficient carbon-neutral chemical synthesis.