High-loading single-atom tungsten anchored on graphitic carbon nitride (melon) for efficient oxidation of emerging contaminants

Single-atom catalysts (SACs) have become an attractive concept in heterogeneous catalysis because of its high activity, selectivity and maximized utilization efficiency. However, constructing a high-loading SACs through conventional pyrolysis methods remains a challenge, because metal precursors usually have low thermal stability and the decrease of particle size will lead to an increase of surface energy. Herein, we used dicyandiamide to tailor the metatungstate and fix the W atoms during the thermal polymerization process, finally obtained a new kind of W-SAC (single W atoms anchored on graphitic carbon nitride, named as W-CN) with a high-loading of 11.16 wt% and a unique O, N coordination. The electrospray ionization high-definition mass spectrometry (ESI-HDMS) revealed that single W atoms were introduced into graphitic carbon nitride via the polycondense of W-containing dicyandiamide intermediate. The unique atomically dispersed N-W-O3 moieties, which promoted the separation efficiency of photogenerated electron-hole pairs, were identified by Aberration-corrected scanning transmission electron microscopy (AC-TEM), X-ray photoelectron spectroscopy (XPS), X-ray absorption fine structure spectroscopy (XAFS) and Density functional theory (DFT) calculation. Moreover, compared to pure CN, the W-CN exhibited an enhanced catalytic performance for the oxidation of carbamazepine (CBZ) under solar light irradiation. The experiment results revealed that photogenerated holes (h+), superoxide radicals (•O2−), and singlet oxygen (1O2) were the predominant active species and played an important role in eliminating emerging contaminants. This work paves a facile and efficient path toward high-loading SAC, and opens new insight into tracking SAC structure evolution.