Executive Summary : | Electrochemical water splitting, which is powered by renewable energy, is seen as a promising way to produce green hydrogen. In which, the cathodic hydrogen evolution reaction (HER), the anodic oxygen evolution reaction (OER), and the membrane between them to prevent the mixing of H2/O2 make up the majority of the standard water electrolysis system. The kinetics of HER and OER, overpotential, and membrane resistance are the limits of this technology's reaction rate and energy consumption. The HER and OER are tightly coupled in both time and space in traditional water electrolysis and this makes several challenges in practical implementation. This is the outcome of some factors like: (i) crossover of O2 and H2 into the cathode and anode compartments respectively;(ii) hydrogen is produced at the cathode as oxygen is simultaneously generated at the anode;(iii) variable power outputs from renewable leads to gas crossover results in the explosive O2/H2 mixtures; (iv) mixing reduces the harvesting hydrogen, which lead to the production of reactive oxygen species that severely degrade cell components and hence shorten the electrolyzer’s lifespan; and (v) proton exchange membrane or diaphragm increases the cost and internal resistance of electrolyzer. Decoupled membrane free electrolysis is promising strategy to overcome the above mentioned limitations. In decoupled electrolysis system, the HER and OER are independent in both time and space which containing anode and cathode made with electrocatalyst and redox solid state redox mediator for HER and OER, hence it is an efficient methodology. Considering above in this proposal, the following tasks were proposed: (1) To fabricate the transition metal based redox mediators of M(OH)2 and transition metal based bifunctional catalyst by hydrothermal or electrodeposition techniques. (2) To study the physicochemical properties of M(OH)2 and M-N(OH)2 (M, N =Ni, Co, Mn, Fe) catalytic materials with suitable analytical techniques. (3) To correlate the redox mediator performance with the reversible transformation and charge/discharge capacities will be studied through cyclic voltammetry and galvanostatic charge/discharge tests. (4) To study the electrocatalytic performance and stability of transition metal-based binary and ternary bifunctional electrocatalysts, through various electrochemical techniques. (5) To enhance the charge storage/discharge property of redox mediator and electrocatalytic performance of materials via tuning size, shape, and crystallinity of the material, and by changing their composition. (6) To construct a membrane-less electrolyzer with a solid redox mediator M(OH)2 and a bifunctional electrocatalyst M-N(OH)2 for the overall alkaline electrolysis of water. |