Interfacial Coordinational Bond Triggered Photoreduction Membrane for Continuous Light-Driven Precious Metals Recovery

Chemical/electric energy-driven processes dominate the traditional precious metal (PM) recovery market. The renewable energy-driven selective PM recycling approach crucial for carbon neutrality is under exploration. Herein, via an interfacial structure engineering approach, coordinational-active pyridine groups are covalently integrated onto the photoactive semiconductor SnS₂ surface to construct Py-SnS₂. Triggered by the preferred coordinational binding force between PMs and pyridine groups, together with the photoreduction capability of SnS₂, Py-SnS₂ shows significantly enhanced selective PM-capturing performance toward Au³⁺, Pd⁴⁺, and Pt⁴⁺ with recycling capacity up to 1769.84, 1103.72, and 617.61 mg/g for Au³⁺, Pd⁴⁺, and Pt⁴⁺, respectively. Further integrating the Py-SnS₂ membrane into a homemade light-driven flow cell, 96.3% recovery efficiency was achieved for continuous Au recycling from a computer processing unit (CPU) leachate. This study reported a novel strategy to fabricate coordinational bonds triggered photoreductive membranes for continuous PM recovery, which could be expanded to other photocatalysts for broad environmental applications.

Bandgap Shrinkage and Charge Transfer in 2D Layered SnS2 Doped with V for Photocatalytic Efficiency Improvement

Effects of electronic and atomic structures of V-doped 2D layered SnS₂ are studied using X-ray spectroscopy for the development of photocatalytic/photovoltaic applications. Extended X-ray absorption fine structure measurements at V K-edge reveal the presence of VO and VS bonds which form the intercalation of tetrahedral OVS sites in the van der Waals (vdW) gap of SnS₂ layers. X-ray absorption near-edge structure (XANES) reveals not only valence state of V dopant in SnS₂ is ≈4⁺ but also the charge transfer (CT) from V to ligands, supported by V L_α,β resonant inelastic X-ray scattering. These results suggest V doping produces extra interlayer covalent interactions and additional conducting channels, which increase the electronic conductivity and CT. This gives rapid transport of photo-excited electrons and effective carrier separation in layered SnS₂ . Additionally, valence-band photoemission spectra and S K-edge XANES indicate that the density of states near/at valence-band maximum is shifted to lower binding energy in V-doped SnS₂ compare to pristine SnS₂ and exhibits band gap shrinkage. These findings support first-principles density functional theory calculations of the interstitially tetrahedral OVS site intercalated in the vdW gap, highlighting the CT from V to ligands in V-doped SnS₂ .

Tin sulphide nanoflowers anchored on three-dimensional porous graphene networks as high-performance anode for sodium-ion batteries

The SnS₂ nanoflowers anchored on three dimensional porous graphene were easily constructed with nickel foam (NF) as supported backbone through the dip-coating method followed by one-step controllable hydrothermal growth and mild reduction. The interconnected SnS₂ nanoflowers with cross-linking nanosheets and rich pores assembled to form one layer of continuous network structure, which tightly adhered on the surface of graphene. The porous graphene supported by NF built a conductively integral highway that is preferable for the charge transfer kinetics, while the hierarchical pores from the SnS₂ nanoflowers and NF are particularly beneficial for mitigating the volume expansion and promoting electrolyte penetration. The as-constructed Ni foam/reduced graphene oxide/SnS₂ (NF/RGO/SnS₂) composite exhibited dramatically enhanced reversible capacity, remarkable rate capability, and long-term cycling stabilities without the use of any binders and conductive additives. Especially, NF/RGO/SnS₂ composite remained the specific capacity as high as 561.9 mA h g^-1 at the current densities of 1000 mA g^-1 after continuous tests for 160 cycles, which is much higher than conventional SnS₂/RGO composite. With the advantages of unique architecture and excellent sodium storage performances, the NF/RGO/SnS₂ composite shows promising application potential in the sodium ion batteries.

Strain tunable magnetism in SnX2 (X = S, Se) monolayers by hole doping

By first-principles calculations, the magnetism of hole doped tin dichalcogenides SnX₂ (X = S, Se) monolayers is systematically studied. It is found that a phase transition from nonmagnetic to ferromagnetic ground state appears once above the critical hole density (~10¹⁴ cm⁻²). The spin magnetic moment can maintain a magnitude of 1.0 μ_B/hole with excellent stability of ferromagnetic state. Furthermore, we demonstrate that strain is very useful to modulate the DOS near the valence band, resulting in the reduction of the critical hole density to ~10¹³ cm⁻² when the strain reaches 4% (6%) in SnS₂ (SnSe₂), which can be realized in common field effect transistors. Moreover, the phonon dispersion calculations for the strained SnX₂ monolayers indicate that they can keep the dynamical stability under the hole doping. Therefore, the strain tunable magnetic transition in hole doped tin dichalcogenides indicates their potential promising applications in spintronic devices.