Unveiling the Role of Pyridinic Nitrogen and Diacetylene in the Hydrogen Evolution Reaction through Model Catalysts Prepared by On-Surface Reactions

Metal-free carbon materials (MFCMs) have extensive applications in electrocatalysis because of their comparable catalytic activity to that of Pt/C in some cases. Understanding the structure-property relationship is crucial for the reasonable design of more efficient catalysts. To reveal the structure-property relationship of the hydrogen evolution reaction (HER), we prepared nanowire model catalysts on single-crystalline Au(111) electrodes through state-of-the-art on-surface synthesis. Temperature-dependent experiments were conducted to evaluate the HER activity of the nanoribbons functionalized with pyridinic nitrogen and diacetylene. According to our electrochemical results (overpotential, current density <i>j</i>₀, and apparent activation energy), we demonstrate that the participation of diacetylene can promote the catalytic reaction for the HER through a synergistic effect. Based on the analysis of the activation entropy for the model catalysts, we attribute the synergistic effect of diacetylene groups to the large area of π···H-O bonding in the electric double layer, thus providing direct insight into the structural-property relationship of polymerized nanoribbons for the HER through the rational design of precursor structures. The nanoribbons prepared by on-surface synthesis can serve as prototype systems for model catalytic research on MFCMs.