Supramolecular Assembly of Graphene–Polyamine–PdS–CdS Photocatalysts for Synergistically Enhanced and Highly Effective Hydrogen Evolution from Water under Visible Light

Abstract

New composite materials for water reduction based on the CdS photocatalyst were prepared by sequential deposition of semiconductor PdS and CdS on a platform obtained from graphene nanoplatelets (GNPs) noncovalently functionalized by the adsorption of the [9]aneN3 pyrimidine derivatives HL1 and H2L2. The GNP-HL1-PdS-CdS composite (≈ 4.5, 0.5, 95 wt % composition) showed excellent photocatalytic activity in water reduction with an almost constant average H2 production of 4.05 mmol·g−1 ·h−1 during 28 h, overcoming the best-performing analogous composites reported so far. The systematic study of the structural and optical properties of both the composites and the precursors reveals that besides PdS and CdS, GNP-HL1 behaves as a 2D semiconductor. The excellent performance of the GNP-HL1-PdS-CdS composite in water reduction is explained by the suitable alignment of VB and CB of CdS, acting as a photocatalyst, to those of both PdS and GNP-HL1, acting as cocatalysts. The small size of GNP sheets, together with the chemical nature of HL1 functions, facilitates the light activation of the sites of the photocatalysts, resulting in effective water reduction at the surface of both CdS and GNP-HL1 components.