Behzad Rezaei, Maryam Mokhtarianpour & Ali Asghar Ensafi

Abstract
In this work, a 304 stainless steel (SS) was anodized to prepare nanoporous SS (NPSS) with an average size of about 75 nm and then filled with copper (Cu/NPSS) using pulsed electrodeposition method. Afterward, a nanostructural Pt and Pd film was deposited by galvanic replacement (GR) on the Cu/NPSS to prepare modified electrode (PtPd/Cu/NPSS) for hydrogen evolution reaction (HER) and formic acid electrooxidation (FAO). The electrocatalytic activity of the modified electrode and its structural characterization have been studied by voltammetric methods, electrochemical impedance spectroscopy
(EIS), inductively coupled plasma optical emission spectrometry (ICP-OES), and field emission scanning electron microscopy (FESEM). The results show that the nanostructural Pt1Pd1/ Cu/NPSS composition, with low Pt loading and suitable stability, has a good electrocatalytic performance toward HER (EOnset = + 12 mV vs. NHE) and FAO (EOnset = −180 mV vs. NHE). For HER observed a high mass activity of noble metals (87.54 mA cm−2μg−1 Pd+Pt) in comparison with Pt deposited Cu/NPSS (41.5 mA cm−2 μgPt −1) at the same applied potential of − 0.25 V versus NHE. Also, the fabricated electrocatalysts
with more electrochemically active surface area in comparison with Pd/Cu/NPSS and Pt/Cu/NPSS revealed more resisting to the poisoning components and good stability for FAO.

Keywords Nanoporous stainless steel · Galvanic replacement · Nanostructural PtPd · Pulsed electrodeposition · Hydrogen
evolution reaction · Formic acid oxidation