Influence of antisite defects on two-dimensional polymeric material for improved hydrogen evolution reaction

Abstract

Two-dimensional materials (2D) supported by single atom catalysis have emerged as effective catalysts for H2 production at large scale by Hydrogen Evolution Reaction (HER). While there is a research surge on utilizing inexpensive metals as catalysts to replace Platinum (Pt) and other related noble metals, their practical limitations such as oxidation issues remain a concern. In this work, we report electrochemical HER activity of a recently synthesized metal-free 2D Polyaramid (2DPA) using Density Functional Theory (DFT) calculations. Pristine 2DPA exhibits remarkable HER performance in terms of active sites availability for hydrogen adsorption and the lowest Gibb's free energy change (−0.06 eV) close to that of benchmark Pt/C catalyst (−0.09 eV). Furthermore, introduction of antisite defects by substituting carbon for nitrogen (CN) and nitrogen for carbon (NC) in pristine 2DPA depicts enhanced HER activity. CN and NC defects tune the electronic properties by reducing the band gap resulting improved conductivity. Low formation energies calculated for obtaining antisite defects confirm their feasibility of synthesis while ab initio molecular dynamics (AIMD) simulations ensure their thermal stability at room temperature. The change in Gibb's free energy (ΔGH) values for CN-defective and NC-defective 2DPA are computed to be −0.13 eV and −0.11 eV, respectively. Both CN-defective and NC-defective 2DPA favor H2 evolution via Heyrovsky reaction pathways due to their relatively lower activation energy, 0.64 eV and 0.51 eV, respectively. Our findings encourage design and development of a novel 2D metal-free electrocatalyst for enhanced HER.