Colloidal Cu2-xS and CuInS2 Nanomaterials for Photocatalytic Applications

Abstract

The aim of this thesis is to synthesize Cu2-xS and CuInS2 based nanocrystals (NCs) and to perform different photocatalytic experiments with these materials. Cu2-xS and CuInS2 NCs have several benefits in comparison to other NCs such as their small bandgap in the NIR that can absorb light in the visible range, low toxicity and environmental impact and high tunability of shape, size and stoichiometry. Cu2-xS NCs are synthesized, from which CuInS2 NCs of different size and shape are synthesized with partial cation exchange. Cation exchange is used so that the resulting CuInS2 NCs have the same size and shape as the template Cu2-xS NCs, which makes comparison between the Cu2-xS and CuInS2 NCs more qualitative. CuS nanoplatelets are synthesized to study the effect of excess holes on Rhodaminde B (RhB) degradation, since these materials are known to be p-doped. Cu2-xS, CuInS2 and CuS NCs are investigated for photocatalytic RhB degradation. The Cu2-xS and CuInS2 NCs do not show photocatalytic activity for RhB degradation. CuS nanoplatelets do degrade RhB, but this reaction is non-photocatalytic. Cu2-xS-CuInS2 heteronanorods (HNRs) with different lengths are synthesized with the seeded injection method to study the influence of a heterojunction on the photocatalytic activity of a NC. The length of the rods can be tuned by varying of the reaction time. Furthermore, it is observed that CuInS2 nucleates on one side of the Cu2-xS seeds. The copper content of the Cu2-xS segment decreases as the rods increase in length, because the copper of Cu2-xS is used as the copper source for the CuInS2 segment. To be able to perform photocatalytic experiments, phase transfer is done. After phase transfer assembled clusters of Cu2-xS-CuInS2 HNRs are observed, suggesting that the interface during phase transfer possesses a 2D directing effect. The Cu2-xS-CuInS2 HNRs and Cu2-xS seeds are not active for MV2+ reduction. The HNRs do possess activity for H2 generation, but this activity is low.