Recycled Steel from Waste Dead Nickel–Metal Hydride (Ni–MH) Batteries as Efficient Bifunctional Electrodes for Water Splitting: Ideal Way from Waste to Energy

The introduction of electronic devices has made lives easier, but at the same time, the waste produced from these devices presents a potential threat to the upcoming generations if not handled properly. In the present work, we have shown a strategy for the direct use of e-waste generated from dead nickel–metal hydride batteries (Ni–MH) as bifunctional electrocatalyst materials for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). For OER, the activated and area-normalized recycled untreated steel plate (Act-SP) and steel mesh (Act-SM) show overpotentials of 310 and 290 mV with 100% iR correction at a current density of 10 mA cm–2 and turnover frequencies (TOFs) of 0.162 and 0.135 s–1 respectively. Similarly, the HER requires overpotentials of 272 and 217 mV for SP and SM, respectively. The SP and SM, with their suitable Ni and Fe ratio, show higher OER activity than commercial Ni-foam (NF) and noble-metal-based mixed metal oxide (MMO) catalysts, whereas they show very significant HER activity compared to the Pt/C electrode. In addition, the 2-electrode setup constructed using both SM electrodes provides current densities of 10 and 100 mA cm–2 at 1.78 and 1.95 V, respectively, with significant stability for more than 100 h. According to the overall catalytic study, using recycled steel-based electrodes can be considered an important step toward the development of economical, scalable, and efficient electrodes from waste and will pave the way toward clean energy.