Constructing atomic Co1–N4 sites in 2D polymeric carbon nitride for boosting photocatalytic hydrogen harvesting under visible light

Two‒dimensional polymeric carbon nitride (2DPCN) is a versatile support for constructing single atom catalysts (SACs). Herein, we demonstrated a facile strategy for constructing atomic Co sites on 2DPCN. Atomic dispersion of Co was confirmed by the aberration‒corrected high angle annular dark field scanning transmission electron microscopy, while the extended X‒ray absorption fine structure spectroscopy analysis precisely corroborated the existence of atomic Co1–N4 non square planar sites on 2DPCN support. Remarkably, Co1/2DPCN catalyst yielded H2 at a rate of 28.3mmolH2 h−1 gCo−1, which is approximately 4.2 times higher than that of CoNPs/2DPCN (6.8mmolH2 h−1g Co−1) counterpart. Notably, with 0.75 wt % Pt as a co‒catalyst, H2 evolution activity for Co1/2DPCN and CoNPs/2DPCN reached as high as 138.6 mmolH2 h−1 gmetal−1 and 22.4mmolH2 h−1 gmetal−1, respectively, which could be attributed to the synergistic effect of atomic Co1–N4 sites and Pt. Both DFT calculations and spectroscopic results revealed that as constructed atomic Co1–N4 sites, reduced band gap energy, improved light harvesting ability and decreased energy barrier for H2 evolution.