Porous C₃N₄ nanolayers@n-graphene films as catalyst electrodes for highly efficient hydrogen evolution

Abstract

Pt-free electrocatalysts for hydrogen evolution reaction (HER) with high activity and low price are desirable for many state-of-the-art renewable energy devices, such as water electrolysis and photoelectrochemical water splitting cells. However, the design and fabrication of such materials remain a significant challenge. This work reports the preparation of a flexible three-dimensional (3D) film by integrating porous C₃N₄ nanolayers with nitrogen-doped graphene sheets, which can be directly utilized as HER catalyst electrodes without substrates. This nonmetal electrocatalyst has displayed an unbeatable HER performance with a very positive onset-potential close to that of commercial Pt (8 mV vs 0 mV of Pt/C, vs RHE @ 0.5 mA cm⁻²), high exchange current density of 0.43 mA cm⁻², and remarkable durability (seldom activity loss >5000 cycles). The extraordinary HER performance stems from strong synergistic effect originating from (i) highly exposed active sites generated by introduction of in-plane pores into C₃N₄ and exfoliation of C₃N₄ into nanosheets, (ii) hierarchical porous structure of the hybrid film, and (iii) 3D conductive graphene network.