In-situ converting CoO@Co/RGO into Co/Co(OH)2/RGO for improved dye-sensitized photocatalytic H2 evolution

Abstract

It is of huge challenge to develop stable and efficient non-metal based cocatalysts for photocatalytic hydrogen evolution reaction (HER) via dye sensitization. Herein, we demonstrate a composite featuring Co(OH)2 nanosheets embedded with metal Co nanocrystallines on reduced graphene oxide (Co/Co(OH)2/RGO) as a durable cocatalyst, which is obtained from the CoO@Co/RGO composite in dye-sensitized photocatalytic HER process via the dissolution-precipitation reaction of Co element. The large CoO@Co nanoparticles (∼43 nm in diameter) are converted to thin Co(OH)2 nanosheets, and tiny Co nanocrystalllines are exposed on the surface. As a fresh cocatalyst, Co/Co(OH)2/RGO is endowed with favorable adsorption sites of both hydrogen and hydroxyl. Such a phase and structure transformation leads to the high photocatalytic activity (136.1 μmol) of Co/Co(OH)2/RGO cocatalyst via dye sensitization, which is 3.7 times as much as that of pristine CoO@Co/RGO (36.7 μmol). The improved HER performance should be highly related to the more effective interfacial electron transfer ability, as reflected by transient absorption decays, and photocurrent test. Moreover, the Co/Co(OH)2/RGO cocatalyst shows a remarkable stability of photocatalytic H2 evolution, as well as the structural and phase stability. This work provides a novel route to develop highly dispersive and efficient non-noble metal based cocatalysts, and a new vision to understand the dynamic structure–activity relationship of the cocatalysts.