Abstract
Development of hydrogen as clean and efficient energy carrier for future is imperative. Water electrolysis, is considered as one of the most promising ways to realize large-scaled hydrogen production. However, a big obstacle of it is to reduce the electric energy consumption for water oxidation in the anode. Engineering of hierarchical architectures on the electrocatalysts could provide abundant active sites and thus boost the sluggish reaction kinetics of water oxidation. Herein, a sequential synthesis method is developed for in-situ growth of ultrathin Co9S8 nanosheets vertically aligned on N and S co-doped reduced graphene oxide (Co9S8/N,S-rGO) as novel and efficient electrocatalysts for water splitting. This architecture with vertically aligned ultrathin Co9S8 nanosheets on N,S/rGO is adopted to facilitate the electron transport and exposure of active sites. Benefiting from the synergetic catalysis between Co9S8 nanosheets and N,S/rGO, Co9S8/N,S-rGO presents remarkable electrocatalytic activity towards oxygen evolution with a low overpotential (266 mV to achieve current density of 10 mA cm−2), small Tafel slope of 75.5 mV dec−1, and good durability in alkaline medium. This remarkable OER electrocatalytic activity is outperforms most of the known noble-metal-free electrocatalysts.
Highlights
With the increasingly serious consumption of fossil fuels and environmental pollution issue, the searching for clean and sustainable energy sources is imperative[1,2]
Li et al reported the in-situ growth of transition metal dichalcogenides (TMDs) nanocages encapsulated by reduced graphene oxide (rGO), which greatly improved the ion/electron transport along the interfaces and efficiently mitigated volume dilation during LIBs delithiation[34]
This Co9S8/N,S-rGO hierarchical architectures which Co9S8 nanosheets with thickness of 3∼4 nm vertically and densely grew on N,S-rGO nanosheets were favoured for exposing surface actives sites and facilitating electron transport, which exhibited high-efficient oxygen evolution electrocatalytic performance and robust durability for electrolytic water in alkaline media
Summary
With the increasingly serious consumption of fossil fuels and environmental pollution issue, the searching for clean and sustainable energy sources is imperative[1,2]. Cobalt based compounds have been exploited as candidate electrocatalysts owing to their abundance in nature, unique d-orbital electronic structure and low Gibbs adsorption energy These compounds have shown high catalytic activity close to RuO2 towards water splitting[12,13]. Hierarchical structures constructed by ultrathin two-dimensional nanosheets in-situ growth on heteroatoms doped rGO is in favour of exposing more active sites, and shortening the distance of charge diffusion. We integrated a new way of constructing Co9S8/N,S-rGO hierarchical structures through polyol refluxing, sulfurization and calcination process This Co9S8/N,S-rGO hierarchical architectures which Co9S8 nanosheets with thickness of 3∼4 nm vertically and densely grew on N,S-rGO nanosheets were favoured for exposing surface actives sites and facilitating electron transport, which exhibited high-efficient oxygen evolution electrocatalytic performance and robust durability for electrolytic water in alkaline media
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