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Bismuth(III) sulfide (Bi 2 S 3) is a promising cathode material for aqueous zinc ion batteries (ZIBs), yet suffers from serious capacity issues due to its poor electrical conductivity and microstructural degradations. In this work, Bi 2 S 3 anchored on reduced graphene oxide (rGO) is prepared through hydrothermal reaction and is used as cathode material for aqueous ZIBs. Raman and XPS characterizations confirmed that the oxygen bridge in Bi–O–C heterostructures is successfully created during the hydrothermal synthesis. These oxygen bridges are energy favourable in the Bi 2 S 3 /rGO composite materials and serve as the electron transfer channels for rapid charge compensation during Zn2+ incorporation/extraction. Rotating ring–disc electrode (RRDE) measurements demonstrate improved electrochemical stability of the Bi 2 S 3 /rGO composite material compared to pristine Bi 2 S 3. As a result of these improved characteristics, Bi 2 S 3 /rGO composite shows notably better rate performance and cycling stability than unsupported Bi 2 S 3. Ex-situ X-ray diffraction and XPS characterizations indicate that Zn2+ undergoes a reversible conversion reaction with Bi 2 S 3 to form ZnS/Bi0, rather than being intercalated into Bi 2 S 3 crystal interlayers. The rGO substrate forms chemical bonds with bismuth in the composite material, and the strongly anchored bismuth on the rGO through a Bi–O–C bridge enables a highly reversible conversion reaction. As a result, the Bi 2 S 3 /rGO composite with 8 wt% rGO can deliver a reversible capacity of ∼186 mAh g−1 at the current density of 500 mA g−1 after 150 cycles, showing high promise as Zn-ion battery material. [ABSTRACT FROM AUTHOR]

[Display omitted] • Two strategies for covalent attachment of MOFs to graphene are proposed. • High density of COOH groups on graphene leads to 'desert rose' MOF growth. • The 'desert rose' NiCo MOF/graphene composite is superior as OER electrocatalyst. Highly efficient and stable earth-abundant metal electrocatalysts are of great significance for improving water splitting systems and rechargeable metal–air batteries, in which the oxygen evolution reaction (OER) plays a central part. Among other strategies, anchoring metal–organic frameworks (MOFs) onto conductive materials has proven fruitful towards enhancing their OER performance. Here we explore two strategies for covalent functionalization of graphene flakes as templates for in situ growth of a bimetallic MOF (NiCo-H 2 bpydc) that is formed using 2,2′-bipyridine-5,5′-dicarboxylic acid as the organic linker, and Ni2+/ Co2+ (1:1) as the metal nodes. The graphene template modified with low density functional groups preserves the original octahedral shape of 3D NiCo-H 2 bpydc, while functionalization with high density functional groups transforms the MOF octahedra into nanoflowers with 'desert rose' morphology, leading to increased accessible active sites, electric conductivity and enlarged active surface area, thus boosting the OER performance with a small overpotential (241 mV) at 10 mA cm−2 in alkaline solution. This synthetic strategy therefore presents an efficient pathway towards controlling morphology and properties of graphene supported electrocatalytic materials with excellent OER performance. [ABSTRACT FROM AUTHOR]