Two-dimensional (2D) materials have attracted attention for electrochemical energy storage applications because of their unique physical and chemical properties. However, the facile synthesis of thin 2D sheets remains a challenge. Herein, we demonstrate the formation of 3D assembly of thin Co–Al spinel sheets and carbon composite through a facile two steps process: hydrothermal synthesis of CoAl Layered double hydroxide (LDH) followed by heating of this LDH at high temperature to form CoAl2O4/C. This composite with a high specific surface area (SSA) of 102.7 m2 g–1 showed enhanced energy storage application. The CoAl2O4/C is capable of delivering specific capacitance of 1394 F g–1 under 1 A g–1 current density with 87% capacitance retention after 5000 cycles. For asymmetric supercapacitor (ASC), the CoAl2O4/C and activated carbon (AC) were used as cathode and anode, respectively. The device CoAl2O4/C//AC exhibits a high energy density of 76.34 W h kg–1 at a power density of 750.045 W kg–1 with good cyclic durability of 79% after 10 000 cycles. The improved electrochemical activity may be due to the 3D assembly of thin 2D Co–Al spinel nanosheets that allows easy electron and mass transport, high surface area, synergistic interaction among different components, etc. for which Co–Al spinel/C composite will find application in energy storage.

Hydrogen production from water electrolysis is of great interest for attaining sustainable clean energy storage and conversion, but the required working voltage (>1.23 V) in water splitting limits its applications in industrial expansion. Therefore, replacing the oxygen evolution reaction (OER) with a more favorable anodic oxidation reaction, which can provide more valuable products and less working voltage, will be of great significance for the upcoming expansion of hydrogen production in industrial applications. In this report, a two-dimensional (2D) amorphous sheet-like nickel oxide encapsulated on the nitrogendoped carbon (NiO x /CN x ) composite was synthesized for the urea oxidation reaction (UOR) and ethanol oxidation reaction (EOR). Remarkably, the catalyst shows 1.647, 1.378, and 1.354 V vs. reversible hydrogen electrode (RHE) potential at 10 mA/cm 2 current density for OER, UOR, and EOR, respectively, with good stability. The overall water, urea, and ethanol electrolyses of NiO x /CN x were carried out by coupling with commercial Pt/C as a cathode which shows only 1.626, 1.43, and 1.414 V cell potential at 20 mA/cm 2 current density. The catalyst also shows excellent chronopotentiometric and dynamic stability toward all the electrolyses. The high catalytic activity of NiO x /CN x may be attributed to the synergistic interaction between the support and materials, amorphous structure, 2D sheet-like morphology, porous structure, and high electrochemical surface area. This finding shows that NiO x /CN x nanosheets can replace noble metal-based catalysts for efficient anodic oxidation reactions.

A growing interest in the electrochemical conversion of biomass-derived compounds is attributed to the extremely high sustainability of this process, which has the potential to generate value-added products and renewable electricity from biowastes. The design and synthesis of a high surface area-interconnected porous network of metal nanomaterials are desirable for their application in the field of catalysis. In this work, the synthesis of the carbon-supported Ag nanoparticle aerogel (Ag–aerogel–CN x ) for electrocatalytic hydrogenation of 5-(hydroxymethyl)­furfural (HMF) is studied. The conversion of HMF to 2,5-hexanedione (HD) via ring opening using ambient pressure and temperature is demonstrated. Here, water is used as the hydrogen source and silver is used as the metal catalyst, which eliminates the use of H2 gas and the conventional method of hydrogenation that uses high pressure and temperature, which makes this reduction process more practical and efficient to produce HD. We investigated the most favorable potential for high Faradic efficiency and provided a plausible reduction path from HMF to HD. The production of HD is strongly dependent on the cathode potential and the nature of the electrolyte. The tuning of the cathodic potential can give high Faradic efficiency and suppress the other undesired byproducts like H2. A high Faradic efficiency of 78% and selectivity of 77% are observed for the conversion of HMF to HD on Ag–aerogel–CN x at −1.1 V versus Ag/AgCl in 0.5 M H2SO4. This direct six-electron reduction of HMF to HD can provide a new route to produce valuable intermediates from biomass.