Modulation of electronic structure of metal-free graphdiyne via precise nitrogen modification for oxygen evolution reaction

Abstract

The oxygen evolution reaction (OER) is essential for energy conversion and storage but is hindered by sluggish kinetics, low efficiency, and high overpotentials. Although RuO₂ and IrO₂ are efficient catalysts, their high cost and scarcity limit their large-scale application. In contrast, nonmetallic catalysts have gained traction as promising alternatives due to their cost-effectiveness, high stability, and environmental sustainability. The OER efficiency depends on optimal adsorption/desorption of oxygen intermediates, such as *O, OH*, and OOH*, on the catalyst surface. The electronic structure of carbon materials can be optimized via nitrogen doping, which introduces a higher polarity than carbon atoms, thereby optimizing the adsorption free energy of oxygen species during an OER. However, conventional high-temperature pyrolysis methods suffer from limitations such as inaccuracy and high energy consumption. The unique and facile bottom-up synthesis of graphdiyne (GDY) enables precise control over the doping positions of the three sp²-N atoms in GDY (1NGDY, 2NGDY, and 3NGDY) via monomer design engineering. By integrating density functional theory (DFT) calculations with experimental validation, we tailored the adsorption free energy of the oxygen intermediates in the OER, thereby optimizing the rate-determining step of *OOH generation. Among these three kinds of nitrogen-doped GDY catalysts, 3NGDY which incorporates three sp²-N atoms exhibited the optimal electrocatalytic performance, achieving a current density of 10 mA cm⁻² in 1 M KOH with a low overpotential of approximately 310 mV. This study demonstrates the significant potential of GDY-based metal-free catalysts in the development of cost-effective, high-performance electrocatalysts.