Integrated electrocatalytic routes to formic acid: CO₂ reduction and waste polyol electro-oxidation

Electrochemical conversion of carbon dioxide (CO₂) into value-added chemicals offers a promising pathway toward carbon neutrality; however, the energy-intensive anodic oxygen evolution reaction (OER) remains a fundamental bottleneck for overall cell efficiency. In this context, waste polyols, namely, ethylene glycol and glycerol, generated from biodiesel or PET-derived plastics need to be valorised to valuable products to counter environmental issues. Formic acid, in this sense, has emerged as an attractive C₁ product due to its high market demand, ease of separation, and potential role as a hydrogen carrier and for direct application in formic acid fuel cells (DFFC); it can be produced from the aforementioned wastes, viz. CO₂ or polyols. This review critically examines the integrated electrocatalytic routes to formic acid production, coupling the cathodic CO₂ reduction reaction (CO₂RR) with the anodic waste polyol electro-oxidation for integrated dual-stream formic acid or formate production. We systematically analyse the thermodynamic and kinetic aspects of both cathodic and anodic reactions focusing on energy efficiency, cell performance, reaction mechanisms, selectivity, catalyst design and interfacial engineering strategies that govern selective formate generation at both electrodes. Particular emphasis is placed on earth-abundant nano-electrocatalysts and selective metals that enable synergistic catalytic enhancement, highlighting their dual role in lowering cell voltage while generating additional value-added formic acid (or formate). Finally, the key challenges related to catalyst stability, product crossover, and scale-up are identified, and future research directions are proposed to accelerate the development of integrated dual-stream sustainable formic acid production.