Rationally Designed Ag@polymer@2-D LDH Nanoflakes for Bifunctional Efficient Electrochemical Sensing of 4-Nitrophenol and Water Oxidation Reaction

The rational design and demonstration of a facile sequential template-mediated strategy to construct noble-metal-free efficient bifunctional electrocatalysts for efficient oxygen evolution reaction (OER) and electrocatalytic detection of hazardous environmental 4-nitrophenol (4-NP) have continued as a major challenging task. Herein, we construct a novel Ag@polymer/NiAl LDH (designated as APL) nanohybrid as an efficient bifunctional electrocatalyst by a simple hydrolysis method. The well-fabricated APL/GCE exhibited an extensive linear range from 0.1 to 100 μM in optimized conditions. It showed a detection limit (LOD) of 0.0096 μM (9.6 nM) (S/N = 3) for 4-NP in pH 6 by differential pulse voltammetry (DPV). Meanwhile, the newly fabricated APL exhibited outstanding OER activity with a very low overpotential of 259 mV to deliver 10 mA cm^-2 current density (J) at a scan rate of 5 mV/s. The Tafel plot value of APL is low (97 mV/dec) compared to that of the benchmark RuO₂ due to a fast kinetic reaction. Besides, the durability of the electrocatalyst was assessed by a chronoamperometry test (CA) for 36 h at 1.55 mV vs RHE, and the long-term cycling stability was analyzed by using cyclic voltammetry (CV); after 5000 cycles, the electrocatalyst was highly stable. These demonstrated results could lead to an alternative electrocatalyst construction for the bifunctionally efficient electrochemical sensing of 4-nitrophenol and oxygen evolution reaction.

Chemically modified self-doped biocarbon via novel sulfonation assisted sacrificial template method for high performance flexible all solid-state supercapacitor

The development of lignin-based carbon electrodes for high-performance flexible, solid-state supercapacitors in next-generation soft and portable electronics, has received much attention. Herein, a self-doped multi-porous lignin-based biocarbon (SUMBC) has been prepared via a simple sulfonation assisted sacrificial template method for the effective formation of oxygenated C-S-C moieties in the carbon network. In this proposed method, the sulfonate moieties in lignin are responsible for the successful decoration of oxygen enriched C-S-C moieties as well as for creating the optimal multilevel porous architecture (ultra-micropores, micropores and mesopores) in the carbon matrix with a large surface area (3149 m² g^-1). Because the sulfonate functionalities yield more sulfur species and induce further defects into carbon framework, in the activation process, these sulfur functionalities produce additional narrow micropores. Benefiting from the above unique feature, the supercapacitor (SC) with the SUMBC electrode delivers excellent capacitive behavior in both acidic (2 M H₂SO₄) and alkaline (6 M KOH) liquid electrolytes. More prominently, the all-solid state, symmetric supercapacitors assembled by SUMBC show outstanding capacitance of ~140 F g^-1 at 0.5 A g^-1 in two different devices and reveals high energy density (~5.41 W h kg^-1 at 0.5 k W kg^-1 power density) and excellent stability. In addition, the solid-state supercapacitors manifest a remarkable flexibility at different bending angles. Hence, the present work provides a new strategy for the preparation of efficient biocarbons via a facile sulfonation assisted sacrificial template method; moreover, the high-performance all-solid supercapacitors based on sulfonated modified lignin has great potential in the field of portable and wearable energy storage devices.