Facile Solid-Phase Method for Preparing a Highly Active and Stable PtZn-Based Oxygen Reduction/Hydrogen Evolution Bifunctional Electrocatalyst: Effect of Bi-Facet Lattice Strain on Catalytic Activity

The uniform disordered PtZn alloy (d-PtZn) in situ produced on N-doped carbon (NC) nanosheets is first prepared by pyrolyzing bimetallic Pt/Zn polyphthalocyanine containing unique Pt/Zn-N4 units. Experiments and density functional theory (DFT) calculations demonstrate that d-PtZn/NC exhibits superior activity and stability for oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER). The maximum peak power density of d-PtZn/NC in H2/O2 fuel cells is up to 1300 mW cm–2, and the decay for half-wave potential (0.88 V) after 10k cycles is less than 5 mV. For HER, the overpotential at 10 mA cm–2 of d-PtZn/NC (29 mV) is obviously smaller than that of commercial Pt/C (50 mV), and the current density of d-PtZn/NC maintains a steady 94% retention after 10 h of continuous electrolysis. The excellent activity of d-PtZn/NC is mainly attributed to bi-facet lattice strain, in which the degree of compressive strain on the (111) plane and the tensile strain on the (200) plane of d-PtZn is exactly located at the middle positions between bulk Pt and PtZn intermetallics. This subtly changes the d-band center of PtZn and thus allows the adsorption energy for the intermediates to reach the optimal position.