Structural Evolution of Atomically Dispersed Ni/Fe Isolated Single Atoms on N-Doped Graphene By Pyrolysis Strategy for Highly Efficient ORR/Oer

Abstract

Single-atom catalysts (SACs) maximizing the metal utilization, and highlight the exceptional performance in various catalysis fields, attracted tremendous attention in material science and engineering. However, conventional synthesis of SACs involves high energy consumption at high temperature, enormous metal trash, poor yields, greatly impeding their performance. The mechanism of anchoring between metal SACs and carbon substrates is also not appropriately named. Here, we engineered graphene with dual separated metals synthesized by new approach for the efficient and low-cost electrocatalyst for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). We tuned the supportive coordination environments by defects engineering techniques to optimize the catalytic activity. The variation in local coordination showed a strong influence on the chemical reactivity and could be exploited to control the catalytic performance. The electrochemical measurements show that the dual metal-doped nanocarbons enable ORR and OER catalysis at low overpotentials. We verified our new approach experimentally by using aberration-corrected scanning transmission electron microscopy (AC-STEM), X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS). The density functional theory (DFT) calculation demonstration also justifies its working mechanism in detail. Apart from the demonstration of a new metal-doped carbon catalyst, the information garnered from this study will expand on existing knowledge in the field of heterogenous single-atom catalysis, where explanations of our systems may help to elucidate behaviors in other catalytic models.