Biowaste-Derived Three-Dimensional Porous Network Carbon and Bioseparator for High-Performance Asymmetric Supercapacitor

To explore renewable resources and reduce pollution, the common biowaste eggshell membrane (ESM) is utilized for electrode materials and separators in asymmetric supercapacitor. This device includes air-activated ESM carbon as the negative electrode, MnO₂ nanoparticle/chemical-activated ESM carbon as the positive electrode, and natural ESM as the separator, achieving a high energy density of 14 W h kg^–1 along with acceptable power density of 150 W kg^–1 and cycling stability (79% capacitance retention after 1000 cycles). Significantly, the air-activated ESM carbon achieves a superior specific capacitance of 478.5 F g^–1 in 1.0 M Na₂SO₄, and the natural ESM based bioseparator displays an impressive ion conductivity and cycling stability. This work demonstrates an operable way to reuse the common biowaste for renewable energy devices with high performance

Hydrothermally Treating High-Ti Cinder for a Near Full-Sunlight-Driven Photocatalyst toward Highly Efficient H₂ Evolution

A major drawback of conventional photocatalysts like TiO₂ is the limit of only working under ultraviolet irradiation. As a solution, visible-light-driven photocatalysts have been explored in recent years but full-sunlight-driven photocatalysts are still lacking. Herein, multielement-codoped (Mn, Fe, Si, Al, S, F, etc.) TiO₂ nanomaterials were prepared from an industrial high-Ti cinder (HiTi) by a two-step hydrothermal method using NaOH and NH₄F (or H₂O) as morphology controlling agents. The prepared HiTi photocatalyst exhibits a strong absorption at near full-sunlight spectrum (300–800 nm). Among all TiO₂-based photocatalysts without any noble metal cocatalyst, the photocatalytic H₂ evolution rate on NaOH- and H₂O-hydrothermally treated HiTi (HiTi-TiO₂) is remarkably superior to the reference P25 TiO₂ powders by a factor of 3.8 and thus is the highest. However, NaOH- and NH₄F-treated HiTi (HiTi-TiO₂-F) shows a lower photoreactivity than HiTi-TiO₂ does. Mechanistic studies show that the multielement-doped TiO₂ can synergistically harvest full span sunlight to greatly increase light absorption, while suppressing the charge recombination and reducing the reaction barriers for efficient water splitting. Importantly, the amount of produced industrial cinder is huge in China, and it is dumped on the ground in very large mounds, which results in serious pollution. This study may open a promising recycling approach to treat the waste for sustainable energy use