Highly dispersed PtO over g-C3N4 by specific metal-support interactions and optimally distributed Pt species to enhance hydrogen evolution rate of Pt/g-C3N4 photocatalysts

Abstract

Understanding the fundamental chemistry of metal-support interactions during catalyst preparation is essential to develop a highly efficient Pt/g-C3N4 photocatalyst for the H2 evolution reaction (HER). In this study, we prepared Pt/g-C3N4 photocatalysts via a loading process of different Pt contents onto solvothermally treated g-C3N4 (SCN) and a successive hydrogen reduction. The physicochemical interactions between Pt species and O-containing functional groups over SCN were tracked, and we investigated how the interactions influenced the photocatalytic properties and performance of Pt/SCN. During the reduction process, Pt(OH)22+ ions in liquid phase specifically interacted with neighboring C = O groups over SCN, resulting in highly dispersed PtO species via chemical bonding to SCN. Due to the limited number of the neighboring C = O groups over SCN, the chemically bonded PtO species were saturated at a certain amount, and 1Pt/SCN (1 wt% of Pt) showed the highest Pt dispersion in this study. In the reduction process, excess Pt was readily reduced to Pt metallic phase and then agglomerated in Pt clusters at high Pt loadings. Therefore, the highly active and stable Pt2+ sites were uniformly dispersed and immobilized over 1Pt/SCN by specific interactions with the O-containing functional groups, showing an outstanding HER activity per gram Pt (120.6 mmol∙gPt−1∙h−1). However, data for the optical and electrochemical properties demonstrated that 3Pt/SCN (3 wt% of Pt) had the best charge separation efficiency because of the optimal distribution of the Pt species over SCN. Correspondingly, the optimized 3Pt/SCN exhibited the highest HER rate of 1255.52 μmol∙gcat−1∙h−1, which was about 50 times higher than SCN photocatalyst (25.2 μmol∙gcat−1∙h−1).