Nanomaterials for electrochemical CO2 conversion: mechanistic insights and emerging hybrid strategies

Rising atmospheric carbon dioxide (CO 2 ) levels exceeding 400 ppm since 2013 and reaching 36.6 billion tons in 2022 due to fossil fuel combustion have accelerated global climate change, contributing to a 1.2 °C rise in temperature and triggering serious environmental issues such as ocean acidification and extreme weather events. Among emerging mitigation strategies, electrochemical CO₂ reduction offers a promising route to convert CO 2 into valuable fuels and chemicals. This review highlights recent advances in nanomaterial-based CO 2 conversion, focusing on electrochemical processes enabled by catalysts such as metal and metal oxide nanoparticles, graphene, carbon nanotubes, and carbon quantum dots. These nanostructures provide large surface areas, tunable electronic properties, and improved catalytic performance. In-operando characterization techniques including transmission electron microscopy (TEM), X-ray absorption spectroscopy (XAS), Raman spectroscopy, infrared spectroscopy (IR), and electrochemical impedance spectroscopy (EIS) are discussed for their role in offering real-time mechanistic insights that support rational catalyst design. The review also considers photocatalytic, thermocatalytic, and plasma-assisted processes to provide a broader perspective on CO 2 utilization. Strategies such as surface functionalization, hybrid material development, and strain engineering are examined for enhancing efficiency and durability. The review concludes by highlighting challenges and future directions for integrating nanomaterials into sustainable, carbon-neutral technologies.