Preparation Of Graphitic Carbon Nitride Photocatalytic Materials Toward Hydrogen Generation In Seawater

Freshwater scarcity and energy crisis are the major challenges that the world is facing today.Sunlight has always been considered as a sustainable green energy,and how to use sunlight effectively has attracted many researchers to study.The use of sunlight to get hydrogen from seawater with the assistance of photocatalyst is one of the most promising ways to utilize solar energy.The search for a friendly and highly active material for photocatalytic hydrogen production is a hot research topic in the field of photocatalysis.Carbon nitride polymer（g-C₃N₄）is considered as a potential photocatalytic hydrogen production material,because it has the advantages of low cost,simple synthesis,non-toxic,pollution-free and adjustable band gap.In this paper,two highly active and stable photocatalytic materials based on g-C₃N₄ were designed and prepared,and made to be used in marine hydrogen production.The details of the research are as follows:（1）The copper（Cu）-doped g-C₃N₄（Cu-CN）photocatalytic materials were synthesized by a simple in situ polymerization method.The introduction of Cu can effectively adjust the band gap energy of the sample,broaden its response range in the solar spectrum,and inhibit the severe recombination of carriers of g-C₃N₄ material.The photocatalytic hydrogen production performance experiments driven by visible light showed that the marine hydrogen production rate of Cu-CN under optimal conditions was 2881.7μmol g^-1 h^-1,which was 2.2times higher than the freshwater hydrogen production rate.Cyclic stability experiments showed that Cu modified g-C₃N₄ maintained good performance stability for 16 h.This study provides a feasible idea for the preparation of g-C₃N₄-based photocatalysts that are more suitable for marine hydrogen processes.（2）The N vacancy modification and potassium doped g-C₃N₄（KCN-V_N）photocatalytic materials were synthesized by one-step molten salt method.The formation of N vacancies and the introduction of K improve the surface properties of the g-C₃N₄ material and enhance the carrier migration efficiency.The hydrogen production performance of the optimized KCN-V_N in deionized water,simulated seawater and seawater was 2409μmol g^-1 h^-1,10274μmol g^-1h^-1 and 15152μmol g^-1 h^-1,respectively.The high-performance g-C₃N₄-based photocatalytic materials prepared in this study have shown potential for practical applications in the field of marine hydrogen generation.