WxCoyS core-shell grown on hollow-porous carbon fiber (HCF) as synergetic electrocatalysts for efficient water splitting

Porous Carbon Nanofibers Derived from Silk Fibroin through Electrospinning as N-Doped Metal-Free Catalysts for Hydrogen Evolution Reaction in Acidic and Alkaline Solutions

Water electrolysis is considered as one promising strategy for hydrogen production, and thus, preparing electrocatalysts of superior efficiency and low cost for a hydrogen evolution reaction (HER) in a wide pH range is of paramount importance. In this research, N-doped porous carbon nanofibers derived from silk fibroin by KCl chemical activation are successfully synthesized as the metal-free catalyst for the HER under both acidic and alkaline conditions. After chemical activation of KCl, hierarchical porous structures are formed. Besides, it is found that the concentration of KCl in the electrospun membrane will affect the maintenance of the fibrous morphology for the carbonized samples due to the destruction of β-sheets in silk fibroin induced by KCl. The specific surface area of the optimized sample, 4%-SPCNF, increased by nearly nine times compared with that without activation because of the hierarchical pores and large through pores between fibers. Meanwhile, the porosity increases from 59.87 to 80.28% due to the existence of through pores. Moreover, the 4%-SPCNF has remarkable stability and durability since the carbon substrate is resistant against the corrosion of the electrolyte. Our work provides insights into the design and engineering of silk fibroin-derived carbon nanofibers for metal-free catalysts of the HER under acidic and alkaline conditions.

Dual Metal-Loaded Porous Carbon Materials Derived from Silk Fibroin as Bifunctional Electrocatalysts for Hydrogen Evolution Reaction and Oxygen Evolution Reaction

Developing electrocatalysts with high efficiency and long-term stability for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is significant to massively generate hydrogen energy by water splitting. In this work, cobalt and tungsten dual metal-loaded N-doped porous carbon electrocatalysts derived from silk fibroin were successfully prepared through facile carbonization and chemical activation by KCl and applied as efficient electrocatalysts for HER and OER. After chemical activation, the resulting catalysts present a unique hierarchical porous structure with micro-, meso-, and macropores, which is able to expose more implantation sites for catalytic active metals and will in turn promote the efficient diffusion of the electrolyte. The catalyst under the optimized condition (CoW@ACSF) has a specific area of 326.01 m² g^-1. The overpotential at a current density of 10 mA cm ^-2 of CoW@ACSF is 138.42 ± 10.39 mV toward HER and 492.05 ± 19.04 mV toward OER. Furthermore, the overpotential only increases 101.2 mV toward HER and 66.00 mV toward OER after the long-term stability test of chronopotentiometric test over 10 h, which confirms the excellent stability of the CoW@ACSF, owing to its unique carbon shell structure. This work gives an insight into the design and engineering of silk fibroin-derived carbon materials for electrocatalysis toward HER and OER.

Transition metal sulfides meet electrospinning: versatile synthesis, distinct properties and prospective applications

One-dimensional (1D) electrospun nanomaterials have attracted significant attention due to their unique structures and outstanding chemical and physical properties such as large specific surface area, distinct electronic and mass transport, and mechanical flexibility. Over the past years, the integration of metal sulfides with electrospun nanomaterials has emerged as an exciting research topic owing to the synergistic effects between the two components, leading to novel and interesting properties in energy, optics and catalysis research fields for example. In this review, we focus on the recent development of the preparation of electrospun nanomaterials integrated with functional metal sulfides with distinct nanostructures. These functional materials have been prepared via two efficient strategies, namely direct electrospinning and post-synthesis modification of electrospun nanomaterials. In this review, we systematically present the chemical and physical properties of the electrospun nanomaterials integrated with metal sulfides and their application in electronic and optoelectronic devices, sensing, catalysis, energy conversion and storage, thermal shielding, adsorption and separation, and biomedical technology. Additionally, challenges and further research opportunities in the preparation and application of these novel functional materials are also discussed.