Pulsed laser rusted stainless steel: a robust electrode material applied for energy storage and generation applications

In terms of global energy needs, fabrication of robust electrode materials with superior energy storage performance and excellent energy generation activity is significant. We demonstrate for the first time the use of the pulsed laser rusting strategy for transmuting stainless steel (SS) into an active electrode that is used as an energy storage system of supercapacitors (SCs) and as an electrocatalyst for the oxygen evolution reaction (OER). Herein, a bare stainless steel (denoted as BARE-SS) electrode is rusted on a single side (denoted as SSLR-SS) and on double sides (represented as DSLR-SS) by means of a Nd:YAG laser pulse. The unique honey-comb texture of highly conductive Fe–Cr–Ni oxide/oxyhydroxide rust layers causes a shorter diffusion path for electrons and ions. Therefore, the as-rusted electrodes possess preferred electrochemically active sites enabling the effective contact between them and the electrolyte (1 M KOH). The electrochemical measurements reveal that compared with the BARE-SS and SSLR-SS electrodes, the DSLR-SS electrode unveils improved capacitive behavior, including satisfactory areal capacitance (22 μF cm−2 at 5 mV s−1). Meanwhile, the DSLR-SS electrode has concurrently performed well as an electrocatalyst for the OER and can attain a current density of 10 mA cm−2 at a low overpotential of 382 mV with a Tafel slope of 52 mV dec−1. These findings shed light on the economic pathway to prepare pulsed laser rusted metallic alloys and to handle multifunctional challenges in the field of energy.