Regulating the allocation of N and P in codoped graphene via supramolecular control to remarkably boost hydrogen evolution

Abstract

Although, as early as 2014, theoretical investigations have illuminated that nonmetallic heteroatom doped graphene (NHDG) is anticipated to achieve excellent catalytic activity approaching that of platinum for the hydrogen evolution reaction (HER), its actual HER performance, even today, is still worse than that of the transition metal-based catalysts used as benchmarks. The lack of an effective way capable of extensively and precisely modulating the allocation (e.g., the proportion, content and configuration) of heteroatoms in NHDG presents a substantial impediment. Herein, encouraged by our systematic theoretical result that optimizing the heteroatom allocation in graphene could significantly boost the HER performance, we regulate, for the first time, the proportion and content of heteroatoms in N, P codoped graphene (G-NP) accurately by a judiciously designed supramolecular architecture. The key to implementation lies in the well-built H-bonded supramolecular architecture (melamine–phosphoric acid)/graphene oxide assemblies, in which, during the pyrolysis, the architecture of melamine and phosphoric acid functions as not only a “spacer” to suppress the stacking of graphene nanosheets, but also a self-sacrificial dopant for extensively tuning the allocation of N and P in a wide range. The optimal G-NP can acquire a moderate hydrogen adsorption Gibbs free-energy, an enhanced conductivity and a large electrochemical surface area, and display an extremely low overpotential of 106 mV at 10 mA cm⁻² in 0.5 M H₂SO₄ solution, ranking first in the reported NHDG catalysts and outperforming many state-of-the-art metallic catalysts. This work not only presents a cost-effective, efficient strategy to regulate the allocation of heteroatoms in doped graphene but also offers insight for better design and fabrication of advanced NHDG for different applications.