Regulating the electronic state of SnO2@NiFe-LDH heterojunction: Activating lattice oxygen for efficient oxygen evolution reaction

Abstract

In Oxygen Evolution Reaction (OER), catalysts with lattice oxygen, utilizing the Lattice Oxygen Mechanism (LOM), directly participate in oxygen evolution, effectively reducing activation energy. NiFe-Layered Double Hydroxides (NiFe-LDHs), rich in surface hydroxyls, are potential for LOM. However, their stability is challenged in alkaline conditions due to metal cation dissolution from the lattice, limiting catalytic efficiency. In this work, we modify NiFe-LDH by combining hydrothermal and electrodeposition techniques, coupling NiFe-LDH with the metal oxide SnO2. This process creates a heterojunction enriched with oxygen vacancies through interfacial and defect engineering. In 1 M KOH solution, this modified catalyst exhibits an OER overpotential of just 209 mV at a current density of 10 mA cm−2. Furthermore, when the current density is increased to 100 mA cm−2, the overpotential only increases by a modest 46 mV. Subsequent DFT investigations reveal that in the heterostructured system, there is an enhanced overlap between the O 2p and metal 3d orbitals, which optimizes the covalency of the metal–oxygen bond and promotes the participation of lattice oxygen in the reduction reaction. The heterojunction, in concert with oxygen vacancies, aligns the energy bands of oxygen and metal closer to the Fermi level, resulting in improved continuity of electronic orbitals near the Fermi level. This synergistic arrangement significantly reduces the energy barrier for the rate-determining step of the OER, substantiating the improved performance and activation of lattice oxygen.