Combining photocatalytic hydrogen generation and capsule storage in graphene based sandwich structures

Li Yang,Xiang Jiang,Yi Luo,Guozhen Zhang,Peng Cui,Jun Jiang,Xiyu Li,Jin Zhao,Xijun Wang

doi:10.1038/ncomms16049

Abstract

The challenge of safe hydrogen storage has limited the practical application of solar-driven photocatalytic water splitting. It is hard to isolate hydrogen from oxygen products during water splitting to avoid unwanted reverse reaction or explosion. Here we propose a multi-layer structure where a carbon nitride is sandwiched between two graphene sheets modified by different functional groups. First-principles simulations demonstrate that such a system can harvest light and deliver photo-generated holes to the outer graphene-based sheets for water splitting and proton generation. Driven by electrostatic attraction, protons penetrate through graphene to react with electrons on the inner carbon nitride to generate hydrogen molecule. The produced hydrogen is completely isolated and stored with a high-density level within the sandwich, as no molecules could migrate through graphene. The ability of integrating photocatalytic hydrogen generation and safe capsule storage has made the sandwich system an exciting candidate for realistic solar and hydrogen energy utilization.

Highlights

The challenge of safe hydrogen storage has limited the practical application of solar-driven photocatalytic water splitting
The computed dielectric function suggested that bare CN, C2N, C3N4 mainly absorb ultraviolet light (Supplementary Fig. 2), in consistent with their band energy gaps (Supplementary Fig. 3)
Their gaps were narrowed by coupling with GR/GR oxide (GO) layers (Supplementary Fig. 3)[14], enabling the hybrid systems to harvest both visible and ultraviolet photons (Supplementary Fig. 2), and thereby a g-CN

Summary

Introduction

The challenge of safe hydrogen storage has limited the practical application of solar-driven photocatalytic water splitting. The ability of integrating photocatalytic hydrogen generation and safe capsule storage has made the sandwich system an exciting candidate for realistic solar and hydrogen energy utilization. A photocatalyst generates energetic charges to split water into hydrogen (H2) and oxygen (O2) molecules[1], through which solar power is converted to hydrogen power, a clean and high calorific energy resource. The future of widely utilizing hydrogen energy generated from sustainable solar and water resources is hampered by the difficulty of hydrogen collection and storage. The practical utilization of photocatalytic water splitting could not be realized until a cost-effective solution is developed to completely isolate hydrogen from oxygen during reactions and safely store H2 afterwards. Urban and colleagues[19] constructed an environmentally stable GO and Mg nanocrystal composite with atomic thickness, which accomplishes hydrogen storage of 6.5 wt%

Methods

Results

Conclusion