Anchoring Active Pt²⁺ /Pt⁰ Hybrid Nanodots on g-C₃ N₄ Nitrogen Vacancies for Photocatalytic H₂ Evolution

A Pt²⁺ /Pt⁰ hybrid nanodot-modified graphitic carbon nitride (CN) photocatalyst (CNV-P) was fabricated for the first time using a chemical reduction method, during which nitrogen vacancies in g-C₃ N₄ assist to stabilize Pt²⁺ species. It is elucidated that the coexistence of metallic Pt⁰ and Pt²⁺ species in the Pt nanodots loaded on g-C₃ N₄ results in superior photocatalytic H₂ evolution performance with very low Pt loadings. The turnover frequencies (TOFs) are 265.91 and 116.38 h^-1 for CNV-P-0.1 (0.1 wt % Pt) and CNV-P-0.5 (0.5 wt % Pt), respectively, which are much higher than for other g-C₃ N₄ -based photocatalysts with Pt co-catalyst reported previously. The excellent photocatalytic H₂ evolution performance is a result of i) metallic Pt⁰ facilitating the electron transport and separation and Pt²⁺ species preventing the undesirable H₂ backward reaction, ii) the strong interfacial contact between Pt²⁺ /Pt⁰ hybrid nanodots and nitrogen vacancies of CNV facilitating the interfacial electron transfer, and iii) the highly dispersed Pt²⁺ /Pt⁰ hybrid nanodots exposing more active sites for photocatalytic H₂ evolution. Our findings are useful for the design of highly active semiconductor-based photocatalysts with extremely low precious metal content to reduce the catalyst cost while achieving good activity.