Sustainable Hydrogen Production through Electrocatalytic Water Splitting with Manganese and Nickel-Based Catalysts

Abstract

Solar-driven water splitting has potential for sustainable solar energy conversion and storage in the form of fuels. Its practical use requires highly effective yet non-expensive electrocatalysts synthesized from earth-abundant materials. Here we report a new electrocatalytic system with two electrocatalysts based on Mangnese and Nickel for effective electrocatalytic water splitting. We have developed a synthesis method for a manganese-based (MnOx) water oxidation catalytic films in situ fromaqueous media. This method involves two series of electrodepositions by cyclic voltammetry (CV) over different potential ranges to tune the oxidation state of the catalyst, followed by calcination to increase its crystallinity. The resulting film has a morphology of uniformly distributed fibrous nanoscale as well as stable and excellent catalytic performance toward water oxidation. The resulting onset potential is so low that a single AA alkaline battery can be used to power the water splitting process. For the hydrogen evolution reaction, we have developed an electrodeposition method to synthesize Ni/Ni(OH)2 electrocatalysts in situ on conductive surfaces. The new method uses two cycles of CV over a single potential range, producing a film with a large number of Ni(OH)2/Ni interfaces which significantly shifts performance towards that of platinum.The new method involves only two cycles of CV over a single potential range. The resulting catalytic film has a morphology of packed walnut-shaped particles. It has superior catalytic activity and good stability over long periods. To test the functionality of the entire catalytic system, we have connected the two electrocatalysts in tandem and the system has shown stable water splitting functionality with low overpotential.