Minutes periodic wet chemistry engineering to turn bulk Co-Ni foam into hydroxide based nanosheets for efficient water decomposition

Herein, in order to promote the scaled-up manufacturing of efficient nanostructured electrocatalysts, we pioneer a novel ultrafast wet chemistry engineering to turn bulk Co-Ni foam into S activated hydroxide based nanosheets (CoNi-OH|S), with short period less than six minutes. The uniform nanosheets morphology is in-situ formed through designed nitro-hydrochloric acid enhanced corrosion within 30 s, then the nanosheets are naturally oxidized to CoOOH/Ni(OH)₂ (CoNi-OH) when drying in the air. To fully boost the electrochemical activities, S activation is conducted through facile chemical bath in S anion-rich aqueous solution with five minutes. The as formed surface sulfur species could optimize the protons adsorption, thus benefitting the HER electrocatalysis. Besides, the Co³⁺ sites with low coordination are also increased by S activation, which could facilitate the de-protonation of OOH, thus promoting the OER electrocatalysis. Finally, such ultrafast surface engineering derived CoNi-OH|S electrodes afford the relatively low overpotentials of 167 mV for HER and 270 mV for OER at 10 mA cm⁻². This wet chemistry strategy further ensures that the large area self-supported electrodes can be easily prepared within several minutes, which would inspire the large-scale synthesis and practical application of similar electrocatalysts in this field.