A DFT Study on Palladium-Based Bimetallic Catalysts for Direct Synthesis of Hydrogen Peroxide: Core-Shell Approach for Enhanced Selectivity

Abstract

Pd-Au alloy is one of the most researched catalysts for directly synthesizing hydrogen peroxide (DSHP). To overcome the limitations of natural resources, one challenge is to design an alternative catalyst composed of abundant, cheap elements that can be prepared via a cleaner process and exhibit better selectivity than Pd-Au. Using DFT-based analysis, we investigated Pd-based core-shell catalysts, where Pd is the shell and the core is selected from the Ag, Cd, Pt, Au, Hg, Ni, Cu, and Zn group. The descriptors of selectivity (OOH versus O adsorption energies) and reaction rate (O2 versus O adsorption energies) were used to search for a better catalyst. Strong OOH and weaker O adsorption energy characterize the better catalytic selectivity. The stronger adsorption energy of OOH compared to O, the better formation of H2O2. The stronger O adsorption energy compared to OOH, the more likely the formation of H2O is to occur instead of H2O2. We also studied the geometric descriptor, represented by surface elasticity and distortion, by calculating the root-mean-square dislocation when the surface adsorbs O species. We have identified a promising new catalyst, Ni6@Pd32, for the direct synthesis of H2O2.