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Because of its low thermodynamic voltage (0.37 V), the urea oxidation reaction (UOR) is an ideal method to replace the OER, accelerate the anodic oxidation reaction and reduce the energy consumption of overall water splitting. In this work, bimetallic selenide with a hollow nanocube structure exhibits remarkable catalyst activity towards the UOR. A hierarchical MOF-based Prussian blue analogue (PBA) is constructed by growing Ni–Co PBA on an MOF–Ni template. By controlling the reaction time and temperature, the Ni–Co Prussian blue analogue (denoted as PBA@MOF–Ni) has the morphology of nanocubes evenly growing on flower-like MOF–Ni. After the selenide reaction by a solvothermal method, PBA@MOF–Ni is converted to Co–Ni/Se (denoted as PBA@MOF–Ni/Se), which has a structure with hollow nanocubes and maintains the shape of a flower. This hierarchical MOF-based PBA selenide exhibits good catalytic activity due to the addition of MOFs and the synergistic effect of bimetals. PBA@MOF–Ni/Se can be used as both a cathode and an anode in urea electrolysis. In particular for the UOR, the performance of PBA@MOF–Ni/Se is much better than that for the OER. In the performance comparison between urea electrolysis and water splitting, PBA@MOF–Ni/Se∥PBA@MOF–Ni/Se only needs 1.49 V to reach 10 mA cm−2, which is much lower than the voltage required for water splitting.

Highly active, ultra-long duration and cost-effective catalysts are imminently required for the development of electrolytic appliances for H2 generation. Herein, we propose a novel and facile strategy to fabricate P doped CoS2 nanosheet arrays on carbon cloth (Co-S-P/CC) as bifunctional electrocatalysts toward hybrid water electrolysis, in which the tardy anodic oxygen evolution reaction (OER) is substituted by a more favorable kinetic and thermodynamic ethanol oxidation reaction (EOR). Benefitting from the abundant active sites of Co-S-P nanosheets and the robust adhesion between Co-S-P and CC, the binder-free self-supported bifunctional Co-S-P/CC electrodes have satisfactory electrocatalytic activities and stabilities toward the EOR and hydrogen evolution reaction (HER). Notably, owing to the more favorable kinetics and thermodynamics of the EOR compared to those of the OER catalyzed by the Co-S-P/CC electrode, the required cell voltage for hybrid water electrolysis (1.63 V) is remarkably decreased compared to water electrolysis (1.77 V). Furthermore, the oxidation product acetic acid is more valuable than raw ethanol or oxygen from water splitting alone. This work may broaden the horizons in exploring and designing novel electrocatalysts, which can integrate the HER with other small organic molecule oxidation reactions for multifarious energy-related applications.

To meet the ever-increasing need for high-efficiency energy storage in modern society, porous carbon materials with large surface areas are typically employed for electrical double-layer capacitors to achieve high gravimetric performances. However, their poor volumetric performances come from low packing density and/or high pore volume resulting in poor volumetric capacitance, which would limit their further applications. Here, a novel and one-step molten salt synthesis of a three-dimensional, densely nitrogen-doped porous carbon (NPC) material by using low-cost and eco-friendly tofu as the nitrogen-containing carbon source is proposed. Hierarchically porous carbon with a specific surface area of 1202 m2 g−1 and a high nitrogen content of 4.72 wt% and a bulk density of ∼0.84 g cm−3 is obtained at a carbonation temperature of 750 °C. As the electrode material for a supercapacitor, the NPC electrode shows both ultra-high specific volumetric and gravimetric capacitances of 360 F cm−3 and 418 F g−1 at 1 A g−1 (based on a three-electrode system), respectively, and excellent cycling stability without capacitance loss after 10 000 cycles at a high charge current of 10 A g−1 in KOH electrolyte. Moreover, the as-assembled symmetric supercapacitor exhibits not only an excellent cycling stability with 97% capacitance retention after 10 000 cycles, but also a high volumetric energy density up to 27.68 W h L−1 at a current density of 0.2 A g−1, making this new method highly promising for compact energy storage devices with simultaneous high volumetric/gravimetric energy and power densities.

A novel Pd/polyaniline/CFC electrode is prepared by electroless deposition of palladium (Pd) onto three-dimensional polyaniline networks. The polyaniline matrix on the carbon fiber cloth (CFC) in the reduction state is electro-synthesized by cyclic voltammetry and has a lower vertex potential of −0.4 V vs. Ag/AgCl. The particle size of the Pd coated on the polyaniline chains is gradiently distributed. The as-prepared Pd/polyaniline/CFC electrode is characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FITR) and X-ray diffraction (XRD). The hydrogen peroxide (H2O2) electro-reduction reaction in H2SO4 solutions on the Pd/polyaniline/CFC electrode is investigated using cyclic voltammetry (CV), linear sweep voltammetry (LSV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS). The results reveal that the electrode exhibited high catalytic activity and excellent stability in the strong oxidizing solution of H2O2 and H2SO4. Polyaniline itself shows electro-catalytic activity towards H2O2 to some extent involving the chemical–electrochemical (C–E) coupling mechanism.

In this article, direct growth of Co3O4 with different morphologies on nickel foam is successfully achieved via a simple hydrothermal method by changing the volume ratio between ethanol and water. The morphology and structure of the as-prepared samples are examined by scanning electron microscopy, transmission electron microscopy, X-ray diffraction and Fourier transform infrared spectroscopy. The electrochemical performance of the Co3O4 electrodes is investigated as pseudocapacitor material by cyclic voltammetry and galvanostatic charge/discharge test in 3 mol L−1 KOH solution. Results show that the solvent composition plays an important role not only in the morphology but also in the capacitance. Co3O4 with a honeycomb structure obtained from the volume ratio of C2H5OH/H2O = 1 exhibits the highest capacitive performance, 2509.4 F g−1 at 1 A g−1 and 1754 F g−1 at 10 A g−1, which is much larger than that prepared in the pure water and pure ethanol solvent. The electrode also has a satisfactory cycling performance with capacity retention of 74% after 1000 cycles at 10 A g−1. The enhanced electrochemical performance is ascribed to the honeycomb nanostructure allowing facile electrolyte flow which speeds up electrochemical reaction kinetics. These findings may open up the opportunity for optimizing the hydrothermal synthesis conditions to control the morphology and performance of the products.