Unraveling the Oxidation Kinetics Through Electronic Structure Regulation of MnCo 2 O 4.5 @Ni 3 S 2 p-n Junction for Urea-Assisted Electrocatalytic Activity.

A promising strategy to boost electrocatalytic performance is via assembly of hetero-nanostructured electrocatalysts that delivers the essential specific surface area and also active sites by lowering the reaction barrier. However, the challenges associated with the intricate designs and mechanisms remain underexplored. Therefore, the present study constructs a p-n junction in a free-standing MnCo 2 O 4.5 @Ni 3 S 2 on Ni-Foam. The space-charge region's electrical characteristics is dramatically altered by the formed p-n junction, which enhances the electron transfer process for urea-assisted electrocatalytic water splitting (UOR). The optimal MnCo 2 O 4.5 @Ni 3 S 2 electrocatalyst results in greater oxygen evolution reactivity (OER) than pure systems, delivering an overpotential of only 240 mV. Remarkably, upon employing as UOR electrode the required potential decreases to 30 mV. The impressive performance of the designed catalyst is attributed to the enhanced electrical conductivity, greater number of electrochemical active sites, and improved redox activity due to the junction interface formed between p-MnCo 2 O 4.5 and n-Ni 3 S 2 . There are strong indications that the in situ formed extreme-surface NiOOH, starting from Ni 3 S 2, boosts the electrocatalytic activity, i.e., the electrochemical  surface reconstruction generates the active species. In conclusion, this work presents a high-performance p-n junction design for broad use, together with a viable and affordable UOR electrocatalyst.