Constructing interlaced network structure by grain boundary corrosion methods on CrCoNiFe alloy for high-performance oxygen evolution reaction and urea oxidation reaction.

• The EBSD characterization and SEM images indicated that grain boundaries that existed as defects with high energy were preferentially corroded and exposed compared with the internal grains. • The (oxy)hydroxides layer on the surface enhanced the catalytic efficiency and surface wettability, endowing the electrode facile access to the electrolytes. • The high mechanical strength between the substrate and (oxy)hydroxides layer prevented the detachment of the hydroxide layer, ensuring high stability. • Benefiting from its unique structure and constructed surface, CrCoNiFe-12 exhibited a high OER (η 10 = 285 mV) and UOR performance (η 10 = 250 mV). Corrosion engineering is an effective way to improve the oxygen evolution reaction (OER) activity of alloys. However, the impact of grain boundary corrosion on the structure and electrochemical performance of alloy is still unknown. Herein, the vacuum arc-melted CrCoNiFe alloys with interlaced network structures via grain boundary corrosion methods were fabricated. The grain boundaries that existed as defects were severely corroded and an interlaced network structure was formed, promoting the exposure of the active site and the release of gas bubbles. Besides, the (oxy)hydroxides layer (25 nm) on the surface could act as the true active center and improve the surface wettability. Benefiting from the unique structure and constructed surface, the CrCoNiFe-12 affords a high urea oxidation reaction (UOR) performance with the lowest overpotential of 250 mV at 10 mA/cm² in 1 M KOH adding 0.33 M urea. The CrCoNiFe-12||Pt only required a cell voltage of 1.485 V to afford 10 mA/cm² for UOR and long-term stability of 100 h at 10 mA/cm² (27.6 mV decrease). These findings offer a facile strategy for designing bulk multiple-principal-element alloy electrodes for energy conversion. [Display omitted] [ABSTRACT FROM AUTHOR]