Band gap alignment of structured microporous graphitic carbons by N doping and its influence on photocatalytic overall water splitting

Abstract

Hydrogen generation from water using solar light could be a process of paramount importance in the forthcoming decarbonized society. This reaction requires efficient photocatalysts based on earth-abundant elements. Metal-free carbon semiconducting materials are very appealing in this regard. This manuscript shows that N-doping is a convenient strategy to increase the photocatalytic activity of microporous graphitic carbons obtained from the pyrolysis of α-, β- and γ-cyclodextrins. These (N)C carbons exhibit enhanced photocatalytic activity for H₂ generation in the presence of methanol with respect to their undoped analogs. The optimal (N)C material (pore size, 0.65 nm) was the one derived from α-cyclodextrin at a N content of 3.1%, achieving a H₂ productivity of 1.8 mmol g⁻¹ at 4 h in the presence of methanol. These materials also exhibit photocatalytic activity for overall water splitting, although with lower efficiency than for H₂ generation in the presence of sacrificial electron donors. The present results illustrate the tuning of band alignment by N-doping in the graphitic matrix.