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

## TL;DR

A new composite material using graphene and semiconductors efficiently produces hydrogen from water under visible light.

## Contribution

A novel composite photocatalyst with enhanced hydrogen evolution under visible light is developed using graphene and semiconductors.

## Key findings

- The GNP-HL1-PdS-CdS composite achieved a high and stable hydrogen production rate of 4.05 mmol·g–1·h–1 for 28 hours.
- GNP-HL1 acts as a 2D semiconductor, improving the performance of the composite photocatalyst.
- The composite's performance is attributed to the alignment of band structures and efficient light activation at the catalyst surface.

## 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.