Metallic Nanoparticle Catalysts for eCO₂RR: Bridging C1 and Multi-Carbon Product Pathways

CO₂ is a greenhouse gas that contributes to global climate change by absorbing and emitting infrared light. The significant rise in CO₂ concentrations, predominantly from fossil fuel combustion, has resulted in environmental concerns relating to global warming, ocean acidification, and biodiversity loss. Various mitigation strategies are proposed, including carbon capture and sequestration, carbon capture and utilization, and renewable energy integration. The electrochemical CO₂ reduction reaction (eCO₂RR) is gaining popularity for its ability to produce important fuels and chemicals under mild working conditions. Nonetheless, challenges exist due to high costs, limited catalytic efficiencies, and a suitable electrocatalyst. Cu-based catalysts are the only ones capable of converting CO₂ into multi-carbon (C₂─C₃) products. Other metals such as Au, Ag, Cu, Pd, Sn, and Ni are better suited to CO and formic acid (C1) products. In this review, metallic nanoparticles (NPs) electrocatalysts of Cu, Ag and Au were thoroughly studied for the eCO₂RR. The results highlight that metallic NPs with optimized crystal facets, surface states, and nanoscale morphology significantly affect CO₂ reduction activity and selectivity, demonstrating their potential for sustainable electrocatalytic conversion technologies. Recent techno-economic studies have concluded that product specificity, current density, overpotential, and Faradaic efficiency to be critical for eCO₂RR commercial viability.