Design of metal-supported MgO catalysts for electrochemical CO2 reduction to formic acid via the Mott–Schottky effect

Metal-supported MgO heterostructures enable efficient CO 2 reduction to HCOOH by tuning interfacial charge transfer and stabilizing the OCHO* intermediate, thereby regulating selectivity and activity. • Metal-supported MgO Mott–Schottky heterostructures enable efficient CO 2 -to-HCOOH. • DFT tuning of interfacial electronic structure optimizes intermediate adsorption. • Interfacial charge transfer governs catalytic activity and product selectivity. • Rational design strategy toward high-performance CO 2 reduction electrocatalysts. Magnesium oxide (MgO) is highly regarded in the chemical industry due to its rich abundance, non-toxic nature, remarkable stability, and distinctive Lewis acid-base characteristics. However, its insulating nature and low dielectric constant have historically limited its use in electrocatalysis, particularly for the electrochemical CO 2 reduction reaction (eCO 2 RR). To overcome this limitation and harness MgO’s potential, we propose a novel class of Mott–Schottky heterostructure catalyst. Using the density functional theory (DFT) calculations, we designed and evaluated a series of metal-supported MgO Mott–Schottky heterostructure catalysts (MgO/M, where M = Cu, Ag, Au, and other transition metals mainly from groups 8–12) for eCO 2 RR. Since the binding strength of key OCHO* intermediates critically governs the eCO 2 RR to formic acid (HCOOH) pathway, we systematically varied the metal species and MgO thickness to modulate the selectivity and activity of HCOOH via the Mott–Schottky effect, where interfacial charge transfer occurs between the metal and MgO. Among the new class of X layer MgO/M (XL, X = 2∼12), we identified an optimal MgO thickness and metal species that enables moderate binding OCHO*. Notably, 7L MgO/Ag exhibits the best catalytic activity for eCO 2 RR towards HCOOH compared with XL MgO/Cu and XL MgO/Au. Additionally, 4L MgO/M heterostructure catalysts (M = Cu, Co, Ni, Rh, and Pd) show comparable performance to 4L MgO/Ag. This study offers theoretical guidance for developing highly efficient electrocatalysts for eCO 2 RR.