Enhancement of photocatalytic H2 evolution of eosin Y-sensitized reduced graphene oxide through a simple photoreaction.

Weiying Zhang,Yuexiang Li,Xiang Cai,Shaoqin Peng

doi:10.3762/bjnano.5.92

Abstract

A graphene oxide (GO) solution was irradiated by a Xenon lamp to form reduced graphene oxide (RGO). After irradiation, the epoxy, the carbonyl and the hydroxy groups are gradually removed from GO, resulting in an increase of sp2 π-conjugated domains and defect carbons with holes for the formed RGO. The RGO conductivity increases due to the restoration of sp2 π-conjugated domains. The photocatalytic activity of EY-RGO/Pt for hydrogen evolution was investigated with eosin Y (EY) as a sensitizer of the RGO and Pt as a co-catalyst. When the irradiation time is increased from 0 to 24 h the activity rises, and then reaches a plateau. Under optimum conditions (pH 10.0, 5.0 × 10−4 mol L−1 EY, 10 μg mL−1 RGO), the maximal apparent quantum yield (AQY) of EY-RGO24/Pt for hydrogen evolution rises up to 12.9% under visible light irradiation (λ ≥ 420 nm), and 23.4% under monochromatic light irradiation at 520 nm. Fluorescence spectra and transient absorption decay spectra of the EY-sensitized RGO confirm that the electron transfer ability of RGO increases with increasing irradiation time. The adsorption quantity of EY on the surface of RGO enhances, too. The two factors ultimately result in an enhancement of the photocatalytic hydrogen evolution over EY-RGO/Pt with increasing irradiation time. A possible mechanism is discussed.

Highlights

Hydrogen is an efficient and green energy carrier
An increase of the irradiation time from 0 to 24 h entails an increase of the absorption strength of the RGOx solution over 291 nm and a red-shift of the absorption
We investigated the effects of the pH value, eosin Y (EY) and RGO24 concentration on the photocatalytic activity for hydrogen evolution over EY-RGO24/Pt

Summary

Introduction

Hydrogen is an efficient and green energy carrier. Photocatalytic water splitting into hydrogen by means of solar energy and semiconductor photocatalysts is a environmentally friendly way to produce storable energy [1,2,3,4]. In order to enhance the activity of photocatalysts for hydrogen evolution, various graphene-based composite photocatalysts, such as graphene/ TiO2 composite and graphene/ZnO composite, have recently been reported [5,6,7,8]. Higher photocatalytic H2 evolution than TiO2 under UV irradiation. This can be attributed to an efficient electron transfer from TiO2 to graphene [9,10]. Single reduced graphene oxide itself (RGO) shows a higher activity as a semiconductor under UV irradiation [11,12]. Yeh et al [12] reported that RGO sheets with in situ photoreduced platinum displayed a high activity for hydrogen evolution from an aqueous methanol solution. The RGO exhibits a very low photocatalytic activity under visible light irradiation

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Conclusion