Recent Developments in Membrane-Free Hybrid Water Electrolysis for Low-Cost Hydrogen Production Along with Value-Added Products.

Water electrolysis using renewable energy is considered as a promising technique for sustainable and green hydrogen production. Conventional water electrolysis has two components - hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) occurring at the cathode and anode respectively. However, electrolysis of water suffers from high overpotential due to the slow kinetics of OER. To overcome this hybrid water electrolysis has been developed by replacing conventional anode oxidation producing oxygen with oxidation of cost-effective materials producing value-added chemicals. This review summarizes recent advances in organic oxidative reactions such as alcohols, urea, hydrazine, and biomass at the anode instead of OER. Furthermore, the review also highlights the use of membrane-free hybrid water electrolysis as a method to overcome the cost and complexity associated with conventional membrane-based electrolyzer thereby improving overall efficiency. This approach holds promise for scalable and cost-effective large-scale hydrogen production along with value-added products. Finally, current challenges and future perspectives are discussed for further development in membrane-free hybrid water electrolysis.