Catalytic conversion of seawater to fuels: Eliminating N vacancies in g-C3N4 to promote photocatalytic hydrogen production.

ABSTRACT

The use of solar energy to decompose seawater and produce hydrogen is of great significance in solving the energy crisis. Numerous studies have shown that vacancies can significantly improve photocatalytic activity due to their electron-rich nature. However, our recent research has shown that materials with vacancies are not suitable for photocatalytic reactions in seawater. In this study, g-C3N4 with rich N vacancies was selected as the research object, and urea was used as the precursor; in this system, the N vacancies in g-C3N4 could be effectively reduced by the addition of ZIF-8 (ZCNQx). The activity of ZCNQ40 was 5.6 times higher than that of g-C3N4 in fresh seawater, but only 3.1 times higher in freshwater. Based on the analysis of the experimental results, we believe that g-C3N4 has a limiting relationship between H+ adsorption catalysis and H2 product desorption. In addition, seawater contains many heteroatoms that will also compete with proton (H+) reduction. The results of our study show that catalysts with vacancies are not necessarily suitable for catalytic reactions in seawater media. This research will stimulate new ideas for research into the conversion of solar energy to chemical energy in seawater media.