Carbon dioxide (CO₂) is a gas naturally present at about 0.04% concentration in Earth's atmosphere, produced by natural processes like animal respiration and decomposition of organic matter. As a greenhouse gas, it traps heat and regulates the planet's temperature. However, human activities such as industry, deforestation, and fossil fuel combustion have significantly increased CO₂ levels over the past 70 years, driving climate change, extreme weather, and sea-level rise. Addressing these challenges requires reducing CO₂ emissions through renewable energy, energy efficiency, reforestation, and technological innovations.

Hydrogen (H₂) is a colorless, odorless gas and the most abundant element in the universe, playing a key role in various chemical processes. It is primarily found in combination with other elements, like in water and organic compounds. Hydrogen has diverse applications, including its use as a clean fuel in fuel cells, where it generates electricity with water as the only byproduct. However, most hydrogen is currently produced from fossil fuels. Developing sustainable production methods, such as electrolysis using renewable energy, is vital for enhancing its environmental benefits and advancing clean energy technologies.

Energy storage is crucial for balancing energy supply and demand, ensuring a reliable and efficient energy system. It encompasses technologies like batteries, thermal storage, and supercapacitors. Lithium-ion batteries are commonly used in electronics, electric vehicles, and grid storage, aiding in grid stability. Thermal storage retains heat or cold for later use, while supercapacitors provide rapid bursts of power for applications like regenerative braking and power backup. Energy storage improves system flexibility, supports renewable energy, and reduces greenhouse gas emissions, making it vital for promoting sustainability.