Artificial Leaves: Bio-Inspired Systems for Sustainable Energy and Environmental Solutions

Leaves are the site of photosynthesis. Photosynthesis is the remarkable natural process by which plants, algae, and certain bacteria convert sunlight, water, and carbon dioxide into oxygen and energy-rich organic compounds. This complex process is broadly divided into two main stages: the Light-dependent Reaction and the Light-independent Reaction (or Dark Reaction). The Light-dependent Reaction captures light energy to produce ATP and NADPH. These products then power the Light-independent Reaction (Calvin Cycle), which fixes carbon dioxide to create sugars. The entire process requires intricate coupling (e.g., in chloroplasts) to ensure the efficiency and regulation of these stages. Artificial leaves are bio-inspired devices that mimic natural photosynthesis to convert solar energy into chemical fuels and sequester CO<sub>2</sub>. These systems integrate light-absorbing materials, catalysts, and biomimetic designs to enable efficient water splitting, hydrogen production, and CO<sub>2</sub> reduction. This review examines principles, recent advancements, and challenges in artificial leaf technology, focusing on system engineering, material innovations, and applications. Notable progress includes solar-to-hydrogen efficiencies above 10% and selective CO<sub>2</sub> reduction using triazine-based membranes. Modern designs prioritize lightweight, flexible, and floating configurations for scalability, allowing deployment on water without land competition. Systems have scaled to 100 cm<sup>2</sup> with 24-hour stability, but durability, efficiency, and manufacturing challenges persist. Future priorities include improving fluid dynamics, mass transport, and catalysts, while exploring multifunctional uses like water purification. Artificial leaves hold transformative potential for sustainable, decentralized energy production and carbon sequestration, particularly in infrastructure-limited regions, by converting CO<sub>2</sub> into valuable products.