Three-dimensional Ni3S2-reduced graphene oxide (rGO) nanosheets composite is directly grown on nickel foam (Ni3S2-rGO@NF) by a one-step hydrothermal process involving in situ sulfurization of NF and reduction of GO. The introduction of GO is found not only to control the aggregation and the growth of Ni3S2 nanosheets, but also to increase the number of active sites and improve conductivity of composite. The heterogeneous Ni3S2-rGO@NF electrode as electrocatalysts for hydrogen evolution reaction (HER) exhibits significantly enhanced catalytic activity in alkaline media. The onset potential of Ni3S2-rGO@NF can be as low as ∼0 mV, which is comparable to platinum, and only a small overpotential of ∼44 mV is needed to reach a benchmark current density of 10 mA/cm2. Moreover, it demonstrates a good stability. All evidences suggest that the in situ surfurization can be considered as an effective way to prepare metal sulfides as electrocatalysts for hydrogen generation.

Intercalated and unmodified TiS2 nanomaterials were synthesized and characterized by UV-Visible-NIR spectroscopy, Powder X-Ray Diffraction, and X-Ray Photoelectron and Ultraviolet Photoelectron Spectroscopy. Photoelectron spectroscopy measurements indicated that CoS and Cu2S appeared to be intercalated between sheets of partially or fully oxidized TiS2, which could be solution processed on conductive oxide substrates. The materials were then applied toward water oxidation and evaluated by cyclic voltammetry, chronoamperometry, and impedance measurements. While unmodified TiS2 was not observed to perform well as an electrocatalyst with overpotentials >3 V in 1 M NaOH electrolyte, CoS intercalation was found to lower the overpotential by ∼1.8–1.44 V at 10 mA/cm2. Conversely, Cu2S intercalation resulted in only a modest increase in performance (>2.3 V overpotential). Impedance measurements indicated that intercalation increased the series resistance in the as-prepared samples but decreased the series resistance in oxidized samples.

Replacing precious and nondurable platinum-based catalysts by economical and commercially available materials is a key issue addressed in contemporary fuel cell technology. Carbon-based nanomaterials display great potential to improve fuel tolerance and reduce the cost and stress on metal scalability. However, their relatively low catalytic activity limits the development and application of these catalysts. In this study, we have synthesized a nitrogen-doped carbon electrocatalyst from metal–organic frameworks and carbon nanotube composites, taking advantage of the existing N in the organic linker in the MOFs with more N added through ammonia treatment. The morphology and composition of synthesized catalysts were characterized by SEM, TEM, XPS, and Raman. The derived catalyst exhibited superior catalytic activity than that of commercial Pt-based catalysts. The N enriched carbon catalyst with high surface area, a graphitic carbon skeleton, and a hierarchical porous structure facilitated the mass and charge transfer during electrolysis.

Developing highly efficient and low-cost electrocatalysts with robust stability for hydrogen evolution reaction (HER) is a significant but challenging work for energy conversion and storage in recent years. In the present work, in situ carbon-decorated Cu3P particles (Cu3P@C) were facially synthesized by a one-pot rapid reaction with the precursors of copper acetylacetonate [Cu(acac)2] and triphenylphosphine (PPh3) at 425 °C for 1 h via a vacuum encapsulation technique. Compared with pure Cu3P particles, the Cu3P@C hybrid catalyst exhibits an enhanced electrocatalytic water-splitting performance for hydrogen evolution with excellent stability. The investigation shows that the hybridization with carbon efficiently facilities the charge transport for the electrochemical reaction. Such results of our study make the present Cu3P@C-based hybrid a promising catalyst for practical applications toward energy conversion and pave way for designing and fast fabricating in situ carbon-decorated HER catalysts from the organometallic precursors.

Recently, highly active, easy-to-make, and efficient bifunctional electrocatalysts have attracted tremendous attention because of their potential applications in clean energy. Herein, we report a simple, one-step approach for fabricating three-dimensional (3D) Ni–P nanorod arrays by direct phosphorization of commercial nickel foam (Ni foam) with different times. When used as a 3D electrode for oxygen evolution reaction, the obtained Ni–P nanorods with two hours of phosphatization treatment display high activity with an overpotential of 270 mV required to generate a current density of 30 mA/cm2 and excellent stability in 1.0 M KOH. Additionally, the Ni–P nanorod arrays are also highly active for electrocatalyzing the hydrogen evolution reaction in the alkaline media. As a result, the bifunctional Ni–P catalysts enabled a highly performed overall water splitting, in which a low applied external potential of 1.6 V led to a stabilized catalytic current density of 10 mA/cm2 over 12 h.

Electrocatalytic water splitting for the production of H2 is increasingly becoming a significant method to mitigate the current energy crisis and environmental pollution. However, oxygen evolution reaction (OER), a slow four-electron progress, is the bottle neck of water splitting. Thus, developing new, low cost, and effective catalysts for OER is a research hotspot in material and energy resource fields. Therefore, the research of nonprecious, metal-based OER catalysts has been popular. In this work, it is validated that 3D hollow Co(OH)2 nanoflowers synthesized by a facile template-based strategy at room temperature are effective electrocatalysts for OER. The catalysts display high activity with a current density of 10 mA/cm2 at an overpotential of 310 mV and a small Tafel slope of 68.9 mV/dec in alkaline condition. It’s noteworthy that this material is stable for over 20 h of chronopotentiometry. This work offers a simple and promising way to prepare efficient and durable electrocatalysts.

Herein, we report the synthesis of Cu(OH)2 nanobelts with high yield at low cost by a simple aqueous solution reaction. The Cu(OH)2-FTO electrode was then fabricated by a facile electrophoresis deposition method with the as-prepared Cu(OH)2 nanobelts, which require no binding agents. By subsequent heat treatment at 300 °C for 2 h, the Cu(OH)2-FTO electrode was converted to the CuO-FTO electrode. The investigation of electrocatalysis of the Cu(OH)2-FTO and CuO-FTO electrodes for water oxidation was conducted in a 0.2 M phosphate buffer solution at pH 12. The CuO-FTO electrode can catalyze water oxidation with an impressive onset overpotential of 370 mV and an overpotential of 500 mV for a current density of 1 mA/cm2 with a low Tafel slope of 57 mV/dec. This facile fabrication strategy is appealing for realizing the practical application of Cu-based electrocatalysts for water oxidation and is expected to be extended to prepare other heterocatalyst electrodes.

The transition metal compound catalysts have been taken a great part in renewable energy conversion and storage systems. Herein, we report the uniform CoFe2O4 nanoparticles with abundant oxygen vacancies and specific active surface exposed through the simple hydrothermal reaction for improving the electrocatalytic performance and stability. They show good electrocatalytic performance for hydrogen evolution reaction in 0.5 M H2SO4 with an onset potential of 20 mV, the overpotential of 45 mV (at j = 10 mA/cm2), and remarkable long-term stability more than 100 h at different current densities and better oxygen reduction reaction activity with lower overpotential in 0.1 M KOH. Moreover, the home-made primary Zn–air batteries, using CoFe2O4 nanoparticles as an air–cathode display the high open-circuit voltage of 1.47 V and the maximum power density of 142 mW/cm2. The two-series-connected batteries fabricated by CoFe2O4 nanoparticles can support a light-emitting diode to work for more than 48 h.

NiO nanoparticles (NPs) were synthesized at different annealing temperatures via a thermal decomposition process and characterized using X-ray diffraction, scanning electron microscopy, and UV-vis spectroscopy. The NiO NPs prepared at higher annealing temperature (400 °C) were shown excellent adsorption and photocatalytic activity toward textile dyes reactive black 5 (RB-5) and methylene blue (MB). About 87.2% of RB-5 in 60 min and 70.2% of MB in 5 h was removed using NiO NPs synthesized at 400 °C. The photocatalytic degradation of MB was found to increase with an increase in the annealing temperature of the catalyst. Moreover, the kinetic study revealed that the adsorption and photocatalytic activity of NiO NPs followed the second and first-order kinetics, respectively. The enhanced performance of NiO NPs toward dye removal might be related to its optical and structural properties.