Engineering Low-Coordination Single-Atom Cobalt on\nGraphitic Carbon Nitride Catalyst for Hydrogen Evolution

Abstract

Although\nsingle-atom catalysts (SACs) have been at the vanguard\nof energy conversion research, the selection of suitable substrates\nand single-atom specification permits remains ambiguous. Herein, we\nfabricated Co-g-C₃N₄/rGO SACs (Co-CNG) by coupling\nthe suitable single-atom Co with a promising substrate of g-C₃N₄/rGO. Remarkably, Co-CNG exhibits even comparable\nHER performance (10 mA cm^–2 at ∼47 mV) with\ncommercially available Pt/C (10 mA cm^–2 at ∼48\nmV) and outperformed non-noble transition-metal SACs under alkaline\nconditions since its mass activity is about 4 times that of Pt/C with\nthe long-term durability of 500 h. Athena fitting of Co-CNG was conducted,\nrevealing its two types of coordination structure, including 20% of\nCo-N and 80% of Co-3N. Notably, the Co-N coordination structure is\nresponsible for boosting HER due to its downshift d-band center, unique\nelectronic structures, and low free energy barriers based on density\nfunctional theory. This study not only reveals that Co-CNG shows HER\nperformance due to its unique SACs coordination of Co-N but also proves\na way for catalyst optimization by specifically coordination engineering\nfor particular applications.