Designing catalysts at atomic level fine-tune the electronic structure of surface-active site for efficient water splitting, is a highly desirable approach but also poses significant challenges. This study focuses on the synthesis of a series of electronically tunable metal single-atom (M−SAs) catalysts: M 9 @S-Ni(OH) 2 (M=Pt, Mn, Fe or Cu). Experimental results reveal that introduction of trace S-heteroatoms and metal atoms into Ni(OH) 2 lattice can effectively modulate the electronic structure of M 9 @S-Ni(OH) 2 through modulation of p-d and d-d orbital hybridization, resulting in exceptional performance in water electrolysis. Among M 9 @S-Ni(OH) 2 , Pt 9 @S-Ni(OH) 2 and Fe 9 @S-Ni(OH) 2 exhibit excellent hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) performance, respectively, the overpotential requiring only 7 mV and 269 mV, respectively, at current density of 10 mA cm −2 . (−) Pt 9 @S-Ni(OH) 2 ||Fe 9 @S-Ni(OH) 2 (+) presents a high current density of 531.07 mA cm −2 at cell-voltage of 1.80 V in overall-water splitting (OWS), which is 14.07 times higher than that of the commercial (−) Pt/C||IrO 2 (+) (37.86 mA cm −2 ) system. This work achieves the development of cost-effective and stable electrocatalysts, offering a solution for large-scale and sustainable water-hydrogen conversion.
The development of composite materials is a key area of research for enhancing the electrochemical performance of electrode materials. In this study, NiCo–S nanostructured hybrid electrode materials were prepared on nickel foam (NF) by using binary metal–organic frameworks (MOFs) as the sacrificial template through a two-step hydrothermal method. Ni–MOF was then deposited on the surface of NiCo–S/NF through the hydrothermal method and subsequently converted into Ni(OH) 2 through a subsequent alkalization treatment. The duration of the Ni–MOF hydrothermal process was varied as a parameter. NiCo–S@Ni–MOF/NF was prepared through hydrothermal reaction for 6 h, 9 h and 12 h, followed by heating in a 6 M KOH solution at 75 ∘ C for 6 h in a water bath. The electrode materials with the best morphology and electrochemical properties were obtained when the hydrothermal reaction time was 6 h. The optimized electrode had a specific capacity of 2533.2 F ⋅ g − 1 at 1 A ⋅ g − 1 and a capacity retention rate of 60.8% at 10 A ⋅ g − 1 , which indicated good rate performance. Additionally, the electrode material demonstrated excellent cycling stability, with a capacity retention rate of 95.3% after 5000 cycles at 50 mV ⋅ s − 1 . The energy density of the hybrid supercapacitor device assembled from this electrode material was 33.5 Wh ⋅ kg − 1 when the power density was 849.89 W ⋅ kg − 1 at a current density of 1 A ⋅ g − 1 .
Exploiting two-dimensional nanomaterials as photo-based theranostic agents is promising for the highly efficient ablation of deep-tissue-buried tumors. However, they are limited by their poor absorption in the second near-infrared-light (NIR-II) bio-window (1000–1300 nm) and intrinsic nonbiodegradability. Herein, defect-rich sulfur-doped Ni(OH)2 (S-Ni(OH)2) nanosheets decorated with bovine serum albumin (BSA) as a novel theranostic agent is developed, which can accomplish multimodal-imaging-guided photothermal ablation of mouse cancers in the NIR-II bio-window. Sulfur doping extends the absorption spectra of Ni(OH)2 nanosheets from the visible to NIR-II bio-window, affording highly efficient photothermal conversion (58.20% for 1064 nm), entailing it to become an excellent contrast agent for photoacoustic imaging. Further, because of their intrinsic paramagnetic property, they can be applied for magnetic resonance imaging. Owing to the abundant defective sites in S-Ni(OH)2 nanosheets, they exhibit response to the tumor microenvironment, resulting in effective biodegradation and excretion from the body. In vivo toxicity experiments indicated that S-Ni(OH)2-BSA NSs delivered no appreciable toxicity and good biocompatibility. This work provides an avenue for the rational design of effective theranostics agents.
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