Integrating Green Chemistry Into Electrochemical Energy Storage: A Review of Bio‐Synthesized Transition Metal Oxides

ABSTRACT Transition metal oxides (TMOs) are widely explored as electrode materials for electrochemical energy storage owing to their rich redox activity, tunable oxidation states, and high theoretical capacitance. However, conventional synthesis routes often rely on toxic chemicals, high‐temperature processing, and energy‐intensive steps, limiting their sustainability and large‐scale applicability. This review highlights recent progress in green synthesis approaches, particularly plant‐mediated, microbial, and agro‐waste‐derived methods that use environmentally benign reducing and stabilizing agents to produce nanostructured TMOs. These green routes enable controlled morphology, enhanced porosity, and defect‐rich architectures, resulting in improved charge storage, rate capability, and cycling stability. A comparative assessment of green‐synthesized and conventionally prepared TMOs is provided, along with insights into synthesis mechanisms, advantages, limitations, and performance trends. Green chemistry–based strategies show strong potential for developing high‐performance, scalable, and eco‐friendly electrode materials for next‐generation supercapacitors and batteries.