CARBON-NEGATIVE GREEN HYDROGEN AND CARBON RECYCLING - Possibly Lucrative and Fast Ways toward Net-Zero Target

A single factor that determines the implementation of green hydrogen is its cost. Currently practiced electrolysis methods are expensive in terms of Capex and Opex. A single factor that determines the Opex is the input energy, which is around ~55 kWh/kg H,, is due to high voltage required for oxygen evolution reaction (OER). How the oxidation can be handled suitably, so that running expenses could be brought down to the lowest level. Concurrently, if oxidation of organic molecules to a value added product can be achieved, instead of OER, it is very likely to bring down the overall cost of hydrogen production. If those organic molecules could come from a waste/bio-waste, it would lead to carbon-negative hydrogen at possibly the lowest cost. Photosynthesis has been going on for millions of years without any issues, but at a low quantum efficiency. How to achieve unassisted, economical, scalable, and sustainable artificial photosynthesis to liquid fuels/products with high solar-to-fuel efficiency (STFE), to address carbon-neutral economy, is a zillion dollar question? An attempt has been made to simulate green photosynthesis in an artificial leaf device to be discussed. Towards this end, sunlight absorbing BiVO, quantum dots is assembled from ionic-precursors into TiO, pores, and integrated them structurally and electronically. This leads to all-inorganic artificial photosynthesis system with sub-quadrillion number of heterojunctions in 1 cm 2 device (contains ~1 mg photoanode material). 30% STFE was demonstrated with the above mentioned artificial leaf device to HCHO and CH OH, and address scalability and sustainability.' Assuming no change in STFE, 6.74 m? device is expected to convert 1 kg/h CO, into C1-oxygenates in sunlight.