Undemanding synthesis of N, P co-doped carbon nanosheets for hydrogen evolution reaction: Combining experimental quantitative analysis and DFT calculation corroboration

Abstract

Developing cost-effective catalyst for hydrogen evolution reaction (HER) is of foremost importance for new energy layout and having broad development prospects. Metal-free heteroatom-doped carbon materials have emerged as a focal point of research due to their low price, superior electrical conductivity, and exceptional corrosion resistance. However, among all the studies, there is a paucity of detailed examinations into the distinct mechanisms of HER activity enhancement of different forms of heteroatomic species on HER activity. To maximize the potential of metal-free heteroatom-doped carbon materials for HER, the respective doping effect on the catalytic activity should be elucidated. Herein, we developed a one-step pyrolysis to synthesize N and P co-doped carbon nanosheets. Chain-structured amino acids are cross-linked with phytic acid to form a huge nanocarbon network that lies flat in two dimensions. The prepared catalyst exhibits an active surface area of 93.5 mF cm-2 and the thickness of the nanoplates was less than 10 nm. The ultra-large active surface area provides the basis for efficient HER. By changing the feeding ratios of precursors, the proportions of different fractions of nitrogen species and phosphorus species showed certain trends. By constructing different double-doping models, the changes in the electron cloud density at the double-doped sites within the local π bonds were related to the changing trends of hydrogen free adsorption energy. Experimental and theoretical analyses indicate that under the electronic perturbation of graphitic nitrogen and C3PO, the surrounding carbon atoms undergo charge polarization, and their ΔGH* is optimized after electron rearrangement, which promotes the HER process.