Interface charge induced self-assembled (Co(OH)2)4@La(OH)3 heterojunction derived from Co4-MOF@La(HCO2)3 to boost oxygen evolution reaction

Interface engineering as an effective material modification method can regulate local corresponding interfacial geometry and electronic structures, thus enabling a higher intrinsic activity for the oxygen evolution reaction (OER). Herein, we carefully designed p-p heterojunction precursor Co4-MOF@La(HCO2)3 with internal electric field through electrostatic adherence, which then in-situ transformed into p-p type heterojunction electrocatalyst (Co(OH)2)4@La(OH)3 under KOH activation strategy. The one-step in-situ conversion of (Co(OH)2)4@La(OH)3 generated the interface with significant difference in metal atomic radius and exhibits fascinating nanostructures, which enhances the specific surface area and increases the number of active sites compared with the parent material. Impressively, the obtained material (Co(OH)2)4@La(OH)3 demonstrates satisfying electrocatalytic activity in OER with a low overpotential of only 233 mV to reach a current density of 20 mA cm−2, and excellent stability for 50 h at 10 mA cm−2 in alkaline medium. In-situ Raman technique indicates that multivalent Co centers are the true active sites during the OER process. Based on density functional theory (DFT) calculation results, La atoms possess empty d orbitals, which are beneficial to facilitate charge transfer from Co to La at the heterojunction interface. Meanwhile, the introduction of La atoms changes the coordinated environment around the adjacent atoms at the interface, which induces the upshift of the d-band center for Co atoms and increases the binding strength of the adsorbed oxygen intermediate.