A strong Jahn–Teller distortion in Mn3O4–MnO heterointerfaces for enhanced silver catalyzed formaldehyde reforming into hydrogen

Abstract

The Jahn–Teller effect has received intense interest in the field of catalysis because of its ability to optimize the surface electron state to tune the adsorption behavior of reactants on catalysts. Herein, direct evidence of a strong Jahn-Teller distortion at Mn₃O₄–MnO heterointerfaces is reported, which is used to regulate the electronic and lattice structures of the Mn₃O₄–MnO composite support and effectively enhance the activity of Ag nanoparticle-catalyzed H₂ production from formaldehyde. Benefiting from the improved density and properties of adsorption sites in Mn₃O₄–MnO by the stabilization of Mn³⁺ at the heterointerface, the lattice distortion affords abundant active sites for reaction intermediate conversion. Therefore, Ag/Mn₃O₄–MnO exhibits the highest catalytic efficiency for formaldehyde reforming into H₂ at room temperature, which is one order of magnitude higher than that of its counterpart catalysts, such as Ag/Mn₃O₄, Ag/MnO and Ag/Mn₃O₄#MnO. Experimental observations and theoretical calculations indicate that the excellent performance can be attributed to the distorted heterointerface, where the Ag NPs and the weak Mn–O bond caused by the strong Jahn–Teller effect are responsible for C–H bond cleavage and O–H activation, respectively. The stabilization of Mn³⁺ at Ag/Mn₃O₄–MnO heterojunction interfaces results in local electron accumulation and a modulated d electron state, facilitating the adsorption of hydrogen-involving intermediates. This work provides new insights into the Jahn–Teller distortion in catalyst engineering to bring about further practical benefits to chemical processes involving sustainable energy conversion.