Repurposing the current collector of a car battery module into a bifunctional electrode for overall electrochemical water splitting

Abstract

Renewable power-driven electrochemical water splitting is rapidly emerging as a viable approach for producing large scale green hydrogen which is free from greenhouse gas emissions. However, there is a continuous need to develop electrocatalysts that are abundant and can be generated with minimal impact on the environment. Here, we explore the possibility of repurposing the anode current collector from a Toyota Prius battery module as a bifunctional electrocatalyst that can be used for overall electrochemical water splitting under alkaline conditions. The Ni coated iron electrode was found to have ideal properties for both the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) while also demonstrating bifunctional behaviour for both reactions upon repetitive cycling. The repurposed material also outperformed a Ni electrode of comparable surface area for both the OER and HER and demonstrated activity that is comparable to chemically synthesised Fe/Ni materials. The key aspect for enabling this behaviour was found to be the emergence of iron into the nickel coating to create a stable mixed FeNi oxide layer upon potential cycling of the electrode. This also resulted in a bifunctional electrode material that could operate between HER and OER without a loss of activity. This work indicates that not only should the active materials used in rechargeable batteries be used for recycling but that the current collectors should also be considered as potentially highly valuable components.