Trifunctional Graphene‐Sandwiched Heterojunction‐Embedded Layered Lattice Electrocatalyst for High Performance in Zn‐Air Battery‐Driven Water Splitting

Abstract

Abstract Zn‐air battery (ZAB)‐driven water splitting holds great promise as a next‐generation energy conversion technology, but its large overpotential, low activity, and poor stability for oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER) remain obstacles. Here, a trifunctional graphene‐sandwiched, heterojunction‐embedded layered lattice (G‐SHELL) electrocatalyst offering a solution to these challenges are reported. Its hollow core‐layered shell morphology promotes ion transport to Co3S4 for OER and graphene‐sandwiched MoS2 for ORR/HER, while its heterojunction‐induced internal electric fields facilitate electron migration. The structural characteristics of G‐SHELL are thoroughly investigated using X‐ray absorption spectroscopy. Additionally, atomic‐resolution transmission electron microscopy (TEM) images align well with the DFT‐relaxed structures and simulated TEM images, further confirming its structure. It exhibits an approximately threefold smaller ORR charge transfer resistance than Pt/C, a lower OER overpotential and Tafel slope than RuO₂, and excellent HER overpotential and Tafel slope, while outlasting noble metals in terms of durability. Ex situ X‐ray photoelectron spectroscopy analysis under varying potentials by examining the peak shifts and ratios (Co2+/Co3+ and Mo4+/Mo6+) elucidates electrocatalytic reaction mechanisms. Furthermore, the ZAB with G‐SHELL outperforms Pt/C+RuO2 in terms of energy density (797 Wh kg−1) and peak power density (275.8 mW cm−2), realizing the ZAB‐driven water splitting.

Keywords

• graphene‐sandwiched structure
• heterojunction
• internal electric fields
• trifunctional electrocatalyst
• water splitting
• Zn‐air battery