Excellent Electrocatalytic Hydrogen Evolution Reaction Performances of Partially Graphitized Activated-Carbon Nanobundles Derived from Biomass Human Hair Wastes

-CoOTe ( = S, Se, and P) with Oxygen/Tellurium Dual Vacancies and Banana Stem Fiber-Derived Carbon Fiber s Battery-Type Cathode and Anode Materials for Asymmetric Supercapacitor

In this work, we demonstrated the synthesis of anions (X = selenium (Se), sulfur (S), and phosphorus (P)) doped cobalt oxytelluride (X-CoOTe) with oxygen and tellurium dual vacancies using hydrothermal methods, followed by selenization, sulfurization, and phosphorization reactions. Especially, the Se-CoOTe-modified nickel foam (Se-CoOTe/NF) electrode delivered a higher specific capacity (752.95 C/g) and an extremely lower charge transfer resistance (0.87 Ω) than S-CoOTe/NF and P-CoOTe/NF due to the higher metallic conductivity of Se. Both oxygen and tellurium vacancies facilitate higher charge transfer conductivity, specific capacity, and stability. On the other hand, banana stem core fiber-derived activated carbon fiber (AC) with exfoliated carbon sheet, cracked surface, and corresponding high surface area boosts the excellent cycle stability up to 4000 cycles with capacitance retention of 100.29%. Thus, the asymmetric device (Se-CoOTe/NF//AC/NF) exhibited an extendable cell voltage (1.55 V), higher energy density (155.6 W h kg-1) at a power density (1356.2 W kg-1), and generous long-term stability (100% retention up to 10 000 cycles) in a liquid alkaline electrolyte. In the practicability test, the proposed asymmetric device mutually showed an increased operating voltage from 1.55 to 4.65 V for a three-series connection. In a three-series connection, a single white LED and an LED string glowed efficiently. This new finding will be very useful to develop tellurium-based chalcogenides and biowaste-derived carbon for energy storage applications.

Waste-Derived Catalysts for Water Electrolysis: Circular Economy-Driven Sustainable Green Hydrogen Energy

The sustainable production of green hydrogen via water electrolysis necessitates cost-effective electrocatalysts. By following the circular economy principle, the utilization of waste-derived catalysts significantly promotes the sustainable development of green hydrogen energy. Currently, diverse waste-derived catalysts have exhibited excellent catalytic performance toward hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and overall water electrolysis (OWE). Herein, we systematically examine recent achievements in waste-derived electrocatalysts for water electrolysis. The general principles of water electrolysis and design principles of efficient electrocatalysts are discussed, followed by the illustration of current strategies for transforming wastes into electrocatalysts. Then, applications of waste-derived catalysts (i.e., carbon-based catalysts, transitional metal-based catalysts, and carbon-based heterostructure catalysts) in HER, OER, and OWE are reviewed successively. An emphasis is put on correlating the catalysts' structure-performance relationship. Also, challenges and research directions in this booming field are finally highlighted. This review would provide useful insights into the design, synthesis, and applications of waste-derived electrocatalysts, and thus accelerate the development of the circular economy-driven green hydrogen energy scheme.