Due to the “ligand effect” and “ensemble effect”, incorporating phosphorus into nickel metal is a promising strategy to prepare an electrocatalyst for the hydrogen evolution reaction (HER). Herein, uniform NiPx nanospheres are deposited on electrode substrates by a simple and fast electrosynthesis method. As expected, the NiPx nanospheres can act as an excellent HER catalyst in a neutral buffer solution. It requires a low overpotential of 230 mV to achieve a current density of 10 mA cm−2, and the stability has been proven to be outstanding by long-term electrolysis.

Sponge-like Ni3N/NC was prepared through a facile approach and was examined as a catalyst for the oxygen evolution reaction (OER). This material can efficiently catalyze water oxidation to reach a current density of 10 mA cm−2 with a small overpotential of 310 mV in 1.0 M KOH aqueous solution. The high efficiency can be attributed to the good electronic conductivity, large specific surface area and fast mass diffusion ability of Ni3N/NC.

Hollow metal oxide materials with nanometer-to-micrometer dimensions have attracted tremendous attention because of their potential applications in energy conversion and storage systems. Numerous efforts have been focused on developing versatile methods for the rational synthesis of various hollow structures to act as efficient water oxidation catalysts. In this work, a unique porous and hollow CoO tetragonal prism-like structure has been successfully synthesized via a facile and efficient co-precipitation method with polyvinylpyrrolidone (PVP K30) followed by a heating treatment of the resulted precipitates. The as-prepared porous and hollow CoO microprisms displayed a high activity and stability for water oxidation in 1.0 M KOH solution. To reach a current density of 10 mA/cm2, a low overpotential of 280 mV is required. The remarkable activity can be attributed to the synergistic effect between two different but well-distributed CoO crystalline phases, uniform particle size, ameliorative crystallinity, high surface area and the low mass transfer resistance benefitted from the unique porous structure.PVP-assisted synthesis of porous CoO prisms is reported. The porous CoO microprisms, which are highly uniform and have discrete tetragonal prism-like structure, display enhanced activity for electrocatalytic water oxidation.Download high-res image (120KB)Download full-size image

The development of new materials/structures for efficient electrocatalytic water oxidation, which is a key reaction in realizing artificial photosynthesis, is an ongoing challenge. Herein, a Co(OH)F material as a new electrocatalyst for the oxygen evolution reaction (OER) is reported. The as-prepared 3D Co(OH)F microspheres are built by 2D nanoflake building blocks, which are further woven by 1D nanorod foundations. Weaving and building the substructures (1D nanorods and 2D nanoflakes) provides high structural void porosity with sufficient interior space in the resulting 3D material. The hierarchical structure of this Co(OH)F material combines the merits of all material dimensions in heterogeneous catalysis. The anisotropic low-dimensional (1D and 2D) substructures possess the advantages of a high surface-to-volume ratio and fast charge transport. The interconnectivity of the nanorods is also beneficial for charge transport. The high-dimensional (3D) architecture results in sufficient active sites per the projected electrode surface area and is favorable for efficient mass diffusion during catalysis. A low overpotential of 313 mV is required to drive an OER current density of 10 mA cm−2 on a simple glassy carbon (GC) working electrode in a 1.0 m KOH aqueous solution.

Water splitting is an attractive way to produce recyclable hydrogen energy resource. The oxygen evolution reaction (OER) is the rate-determine step of water electrolysis. The exploring of low-cost, highly efficient and durable electrocatalysts for OER is thus extremely important. In this work, we developed a facile two-phase protocol to fabricate an α-Co(OH)2 using sodium oleate as the phase-transfer surfactant. The crystallinity and structure of the α-Co(OH)2 was regulated by heat treatments toward enhanced electrocatalytic OER activity. With the calcination of the as-prepared α-Co(OH)2 at 200 °C, a networked and well-dispersed CoO nanoparticles were formed. The CoO sample afforded an OER current density of 10 mA cm−2 under a low overpotential of 312 mV in a 1 mol L−1 KOH aqueous solution. The high activity of the CoO material is believed to be associated with its ultra-small particle size and plentiful open spaces in the material, both of which can provide abundant surface catalytic sites.Download high-res image (184KB)Download full-size image

Aligned cobalt metal nanoparticles were prepared from the pyrolysis of cobalt oxalate nanoplate precursors for efficient electrocatalytic water oxidation. The 2D morphology of the precursor guided the 2D alignment of the derived cobalt metal nanoparticles. The as-prepared Co@CoOx electrocatalyst requires an ultra-low overpotential of 289 mV to achieve a current density of 10 mA cm−2 on a simple glassy carbon (GC) electrode in a 1 M KOH aqueous solution. The metallic nature of the bulk of the electrocatalyst and the compact alignment of the nanoparticles can facilitate the inner- and inter-particulate charge transfers.

•A NiSe/NF electrode was conveniently prepared from electrodeposition method.•The uniform and dense coverage of NiSe on NF provided plentiful surface catalytic sites.•The electrode is bifunctional for both electrocatalytic HER and OER in an alkaline electrolyte.•The electrode is extremely efficient for OER.•A two-electrode water electrolyser based on this janus electrode showed efficient and stable water splitting performance under low cell voltages.Water electrolysis is a feasible way for large-scale production of hydrogen gas. If the electricity is provided by a solar cell, we can convert the sustainable solar energy into chemical energy. In this technology, the development of water splitting electrocatalysts contributes significantly to enhance the solar-to-hydrogen efficiency. Herein, an electrodeposited NiSe/NF electrode is reported with superior electrocatalytic activities for both water reduction and oxidation. A water electrolysis cell was fabricated using this cheap, easily-obtained, efficient and robust electrode as both anode and cathode to achieve high water splitting current density of 20 mA cm−2 at cell voltage around 1.50 V.Download high-res image (179KB)Download full-size image

An ultrathin Fe-based film was prepared by electrodeposition from an FeII solution through a fast and simple cyclic voltammetry method. The extremely low Fe loading of 12.3 nmol cm–2 on indium tin oxide electrodes is crucial for high atom efficiency and transparence of the resulted film. This Fe-based film was shown to be a very efficient electrocatalyst for oxygen evolution from neutral aqueous solution with remarkable activity and stability. In a 34 h controlled potential electrolysis at 1.45 V (vs NHE) and pH 7.0, impressive turnover number of 5.2 × 104 and turnover frequency of 1528 h–1 were obtained. To the best of our knowledge, these values represent one of the highest among electrodeposited catalyst films for water oxidation under comparable conditions. The morphology and the composition of the catalyst film was determined by scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray, and X-ray photoelectron spectroscopy, which all confirmed the deposition of Fe-based materials with FeIII oxidation state on the electrode. This study is significant because of the use of iron, the fast and simple cyclic voltammetry electrodeposition, the extremely low catalyst loading and thus the transparency of the catalyst film, the remarkable activity and stability, and the oxygen evolution in neutral aqueous media.Keywords: electrocatalysis; film preparation; iron; oxygen evolution; water splitting;

Due to the “ligand effect” and “ensemble effect”, incorporating phosphorus into nickel metal is a promising strategy to prepare an electrocatalyst for the hydrogen evolution reaction (HER). Herein, uniform NiPx nanospheres are deposited on electrode substrates by a simple and fast electrosynthesis method. As expected, the NiPx nanospheres can act as an excellent HER catalyst in a neutral buffer solution. It requires a low overpotential of 230 mV to achieve a current density of 10 mA cm−2, and the stability has been proven to be outstanding by long-term electrolysis.