Self-template construction of hollow Co3O4 microspheres from porous ultrathin nanosheets and efficient noble metal-free water oxidation catalysts

Abstract

Developing noble metal-free water oxidation catalysts is essential for many energy conversion/storage processes (e.g., water splitting). Herein, we report the facile synthesis of hollow Co3O4 microspheres composed of porous, ultrathin (<5 nm), single-crystal-like nanosheets via a novel "self-template" route. The successful preparation of these hollow Co3O4 nanomaterials includes three main steps: (1) the synthesis of solid cobalt alkoxide microspheres, (2) their subsequent self-template conversion into hollow cobalt hydroxide microspheres composed of ultrathin nanosheets, and finally (3) thermal treatment of hollow cobalt hydroxide microspheres into the hollow Co3O4 material. The as-obtained hollow Co3O4 nanomaterial possesses a high BET surface area (∼180 m(2) g(-1)), and can serve as an active and stable water oxidation catalyst under both electrochemical and photochemical reaction conditions, owing to its unique structural features. In the electrochemical water oxidation, this catalyst affords a current density of 10 mA cm(-2) (a value related to practical relevance) at an overpotential of ∼0.40 V. Moreover, with the assistance of a sensitizer [Ru(bpy)3](2+) (bpy = 2,2'-bipyridine), this nanomaterial can catalyze water oxidation reactions under visible light irradiation with an O2 evolution rate of ∼12 218 μmol g(-1) h(-1). Our results suggest that delicate nanostructuring can offer unique advantages for developing efficient water oxidation catalysts.

Hierarchically porous Co3O4 architectures with honeycomb-like structures for efficient oxygen generation from electrochemical water splitting

“…H 2 O, OH À and O 2 ) [22,23], but also allows the effective use of such kind of oxide materials with low electronic conductivity to overcome the charge transport limitations [24]. As a result, various Co 3 O 4 structures such as mesoporous nanowires [25], nanocrystalline film [26], porous atomically-thick sheets [27], hollow nanosheet microspheres [28], windmill-shaped microcrystals [29], ordered mesoporous nanocast [30] and mesoporous nanoflakes [31], have been exploited as active electrocatalysts for catalyzing OER in alkaline media.…”

Fabrication of porous nanosheet-based Co 3 O 4 hollow nanocubes for electrochemical capacitors with high rate capability

“…And it is demonstrated that porous hierarchical structures can bring about excellent performances in electrochemical energy storage systems with their high specific surface area. Driven by this, hollow/hierarchical Co 3 O 4 architectures have gained great interest and been successfully synthesized by various methods [19][20][21][22][23][24][25]. Among these methods, chemical templating (sometimes called sacrificial templating) process can provide a straightforward and powerful route for the controllable synthesis of hollow structures [26][27][28].…”

Facile synthesis of ultrafine Co3O4 nanocrystals embedded carbon matrices with specific skeletal structures as efficient non-enzymatic glucose sensors

“…Particularly, its normal spinel crystal structure is favorable for electron transportation between Co 2+ and Co 3+ ions. Currently, Co 3 O 4 and Co 3 O 4 -based composites have exhibited great potential application in supercapacitors [16], batteries [19], heterogeneous catalysts [20], and sensors [21]. However, these Co 3 O 4 -based catalysts usually suffer from the poor electrical conductivity, short active site density, and the dissolution or agglomeration during electrochemical processes.…”