Carbon Capture and Storage — separate CO₂ from a gas stream and store it permanently underground.
Why is amine CO₂ capture reversible?
Absorption is exothermic so cold favours it; heating reverses it (Le Chatelier), releasing pure CO₂ and regenerating the amine.
Acid–base reason CO₂ binds an amine?
CO₂ is a mild acid (acid anhydride); the amine is a base that neutralises it.
Green vs grey vs blue hydrogen?
Green = electrolysis with renewable power; grey = steam reforming of methane (emits CO₂); blue = grey + carbon capture.
Cathode half-reaction in water electrolysis (acidic)?
2H⁺ + 2e⁻ → H₂.
Anode half-reaction in water electrolysis (acidic)?
2H₂O → O₂ + 4H⁺ + 4e⁻.
Minimum theoretical voltage to electrolyse water and why?
1.23 V, from E° = −ΔG°/nF for water formation.
Why is real electrolysis voltage higher than 1.23 V?
Overpotential and internal resistance add kinetic energy cost.
Overall fuel-cell reaction and its E°?
H₂ + ½O₂ → H₂O, E° = +1.23 V (spontaneous).
Why can fuel cells beat combustion-engine efficiency?
They convert chemical energy directly to electricity, avoiding the Carnot limit of heat engines.
How many electrons per H₂ molecule produced?
2 electrons.
Relationship between electrolysis and fuel cell?
Same redox reaction reversed; ΔG and voltage sign flip.
Recall Feynman: explain to a 12-year-old
Water is two hydrogens stuck to one oxygen. If you push electricity through water, you can un-stick them — bubbles of hydrogen gas on one wire, oxygen on the other. That's like charging a battery: you stored energy in the hydrogen. Later, in a fuel cell, you let the hydrogen and oxygen rush back together — they make water again and give you electricity, like a battery running down. The cool part: the only "exhaust" is water. Separately, to clean up smokestacks, we wash the smoke with a special liquid (an amine) that grabs the bad CO₂ gas like a sponge, then we heat the sponge to squeeze the CO₂ back out and bury it.
Dekho, idea simple hai. Fossil fuels jalane se hawa mein CO₂ badhta hai aur planet garam hota hai. Iska ek solution hai carbon capture — smokestack ki gas ko ek amine (base) liquid se dho do, jo acidic CO₂ ko sponge ki tarah pakad leta hai. Phir us liquid ko garam karke CO₂ wapas nikaal lo (Le Chatelier — thanda mein pakdta hai, garam mein chhodta hai) aur zameen ke neeche store kar do. Yahi CCS hai.
Doosra solution hai hydrogen economy. Hum paani ko electricity se todte hain — isko electrolysis kehte hain. Cathode pe H₂ banta hai, anode pe O₂. Thermodynamics minimum 1.23 V maangti hai (kyunki E°=−ΔG/nF), par real life mein overpotential ki wajah se thoda zyada (~1.8–2.0 V) lagana padta hai. Agar yeh electricity solar/wind se aaye to hydrogen "green" kehlata hai. Methane se banao to "grey" (CO₂ nikalta hai), aur grey + capture = "blue".
Ab ulta kaam: fuel cell. Yeh electrolysis ka exact reverse hai — H₂ aur O₂ ko milao, paani banta hai aur saath mein electricity milti hai, E°=+1.23 V. Anode pe oxidation (An-Ox), cathode pe reduction (Red-Cat). Sabse important baat: fuel cell heat engine nahi hai, isliye Carnot limit lagu nahi hota — isliye 50–60% efficiency aaram se mil jaati hai, jabki normal engine sirf ~35%.
Yaad rakho: green hydrogen tabhi clean hai jab electricity clean ho — warna sirf factory shift ho gayi, problem nahi. Aur exhaust sirf paani — yahi iska sabse bada selling point hai.
