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• A novel binary metal sulfide Ni 3 Bi 2 S 2 is predicted to be synthesized from Bi 2 S 3 and Ni powder using DFT calculation. • Ni 3 Bi 2 S 2 proved a high-capacity, high-reversible, and easy-synthesized anode for sodium-ion batteries first. • Heterojunction-like Ni 3 Bi 2 S 2 /NiS-G composites surpassing most of the recently-reported same-type of sodium-ion batteries. In the context of scalable electrode production via ball-milling, achieving high cycling stability and electrochemical performance in bifunctional anodes for sodium ion batteries (SIBs) is crucial yet remains a significant challenge. To address these objectives, we have developed a unique hybrid anode nanocomposite characterized by its local multiphase nature. This composite involves the incorporation of novel ternary-Ni-Bi-S/binary-Ni-S nanomaterials onto exfoliated graphite nanosheets (Ni 3 Bi 2 S 2 /NiS-G) through a facile ball-milling process. Our combined experimental and theoretical investigations suggest that the interactions between graphite nanosheets and the layered structure of Ni 3 Bi 2 S 2 /NiS, along with the discharge products of Na 2 S, play pivotal roles in enhancing the Na+ diffusion rate and stability of the hierarchical configuration anode. Upon testing, the novel Ni 3 Bi 2 S 2 /NiS-G shows overwhelmingly higher electrochemical performance compared to the Ni 3 Bi 2 S 2 /NiS counterpart, the Ni 3 Bi 2 S 2 /NiS-G delivered a reversible capacity of 489.9 mAh/g at 0.2 A/g after 400 cycles, and displayed a high capacity of 387.3 and 339.6 mAh/g after 500 cycles at 1 A/g and 2 A/g, respectively, yielding a high capacity retention ratio of 84.8 % and 82.8 % of the 1st cycle. This work provided a novel approach for developing new bifunctional anode electrodes with high capacity and rate performance as well as superior cycling stability. [ABSTRACT FROM AUTHOR]

[Display omitted] • Multifunctional Co atoms are doped on the twin Mn 0.3 Cd 0.7 S homojunction surface. • Co atoms regulate S electron property and build a fast H-migration channel at S sites. • H migration endows sufficient H to sustain HER and reduces the H 2 evolution barrier. • Co atoms on the cubic phase act as OER active sites to enhance oxidation activity. • The Z-scheme interfacial charge-transfer mechanism is achieved. Low kinetics of water dissociation, unfavorable hydrogen adsorption, and high water-oxidation barriers restrict the photocatalytic overall water splitting (OWS) efficiency over sulfides. Herein, multifunctional Co atoms are doped on the twin Mn 0.3 Cd 0.7 S homojunction surface for efficient photocatalytic hydrogen (H 2) and oxygen (O 2) evolution. An ultrafast hydrogen atom (H*) migration channel bridging the water dissociation/H 2 evolution step is established between cubic-S and hexagonal-S sites by introducing Co atoms, facilitating the HER kinetics. Specifically, Co atoms regulate the electron properties of neighboring S atoms and weaken their charge accumulation, which promotes cubic-S sites to capture sufficient H* from the water dissociation zone and accelerates hexagonal-S sites to release H 2 through the H* migration channel. Meanwhile, unsaturated Co atoms on the cubic phase as oxygen evolution reaction (OER) sites promote water deprotonation and optimize the kinetics of the rate-determining step to form OOH* intermediate, enhancing water oxidation activity. Co atoms strengthen the internal electric field of the homojunction and local polarized electric field by increasing the work function difference between the two phases and introducing the high spin polarization, inhibiting the bulk and surface recombination of photogenerated carriers. The Co 0.01 Mn 0.29 Cd 0.7 S exhibits visible-light-driven H 2 and O 2 evolution rates of 443.12 and 219.67 μmol g−1 h−1, about 50 times that of the Mn 0.3 Cd 0.7 S. This work provides some guidance for the design of homojunction photocatalysts with efficient OWS performance. [ABSTRACT FROM AUTHOR]