Heterogeneous Ni-Boride/Phosphide Anchored Amorphous B-C Layer for Overall Water Electrocatalysis.

The rational design of efficient and economical bifunctional electrocatalysts remained a challenge for overall water electrolysis. In this work, the Ni-boride/ phosphide particles anchored amorphous B-doped carbon layer with hierarchical porous characteristics in Ni foam (Ni3P/Ni3B/B-C/NF) was fabricated for overall water splitting. The Boroncarbide (B4C) power was filled and fixed in the NF interspace through the electroplating and electroless plating, and then annealed in vacuum high temperature. The amorphous B-C layer derived from the B4 C not only speeded up the electron transport, but also cooperate with Ni-boride/phosphide to enhance the electrocatalytic activity for HER and OER synergistically. Furthermore, the hierarchical porous architecture of Ni3P/Ni3B/B-C/NF increased space utilization to load more active materials. The self-supported Ni3P/Ni3B/B-C/NF electrode possessed a low overpotential of 212 and 280 mV to deliver 100 mA cm-2 for HER and OER, respectively, and high stability for 48 h. In particular, the electrolyzer constituted with the Ni3P/Ni3B/B-C/NF bifunctional electrocatalyst only required a voltage of 1.59 V at 50 mA cm-2 for water electrocatalysis under alkaline medium, and demonstrated long-term stability for 48 h. This study provides a new technical path for the development of bifunctional of transition metal borides to promote the application of hydrogen production from water splitting.

S-modified NiFe-phosphate hierarchical hollow microspheres for efficient industrial-level seawater electrolysis.

For sustained hydrogen generation from seawater electrolysis, an efficient and specialized catalyst must be designed to cope with the slow anode reaction and chloride ions (Cl-) corrosion. In this work, an S-modified NiFe-phosphate with hierarchical and hollow microspheres was grown on the NiFe foam skeleton (S-NiFe-Pi/NFF), acting as a bifunctional catalyst to enable industrial-scale seawater electrolysis. The introduction of S distorted the lattice of NiFe-phosphate and regulated the local electronic environment around Ni/Fe active metal, both of which enhanced the electrocatalytic activity. Additionally, the existence of phosphate groups repelled Cl- on the surface and enhanced corrosion resistance, enabling stable long-term operation in seawater. The double-electrode electrolyzer composed of the hollow-structured S-NiFe-Pi/NFF as both cathode and anode exhibited a potential of 1.68 V at 100 mA cm-2 for seawater electrolysis. Particularly, to achieve industrial requirements of 500 mA cm-2, it only required a low cell voltage of 1.8 V and demonstrated a consistent response over 100 h, which outperformed the pair of Pt/C || IrO2. This study provides a feasible idea for the preparation of electrocatalysts that are with both highly activity and corrosion resistance, which is crucial for the implementation of industrial-scale seawater electrolysis.

Nickel Boride/Boron Carbide Particles Embedded in Boron-Doped Phenolic Resin-Derived Carbon Coating on Nickel Foam for Oxygen Evolution Catalysis in Water and Seawater Splitting.

Electrolysis of seawater can be a promising technology, but chloride ions in seawater can lead to adverse side reactions and the corrosion of electrodes. A new transition metal boride-based self-supported electrocatalyst was prepared for efficient seawater electrolysis by directly soaking nickel foam (NF) in a mixture of phenolic resin (PR) and boron carbide (B4 C), followed by an 800 °C annealing. During PR carbonization process, the reaction of B4 C and NF generated nickel boride (Nix B) with high catalytic activity, while PR-derived carbon coating was doped with boron atoms from B4 C (B-CPR ). The B-CPR coating fixed Nix B/B4 C particles in the frames and holes to improve the space utilization of NF. Meanwhile, the B-CPR coating effectively protected the catalyst from the corrosion by seawater and facilitates the transport of electrons. The optimal Nix B/B4 C/B-CPR /NF required 1.50 and 1.58 V to deliver 100 and 500 mA cm-2 , respectively, in alkaline natural seawater for the oxygen evolution reaction.

Three-Dimensional Transition Metal Phosphide Heteronanorods for Efficient Overall Water Splitting.

The development of low-cost electrocatalysts with excellent activity and durability for both the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) poses a huge challenge in water splitting. In this study, a simple and scalable strategy is proposed to fabricate 3 D heteronanorods on nickel foam, in which nickel molybdenum phosphide nanorods are covered with cobalt iron phosphide (P-NM-CF HNRs). As a result of the rational design, the P-NM-CF HNRs have a large surface area, tightly connected interfaces, optimized electronic structures, and synergy between the metal atoms. Accordingly, the P-NM-CF HNRs exhibit a remarkably high catalytic activity for the OER under alkaline conditions and wide-pH HER. For overall water splitting, the catalyst only requires a voltage of 1.53 V to reach a current density of 10 mA cm-2 in 1 m KOH with prominent stability, and the activity is not degraded after stability testing for 36 h. This new strategy can inspire the design of durable nonprecious-metal catalysts for large-scale industrial water splitting.

Electrospun single iron atoms dispersed carbon nanofibers as high performance electrocatalysts toward oxygen reduction reaction in acid and alkaline media.

The metal (Fe/Co), nitrogen co-doped carbon represent an important class of oxygen reduction reaction (ORR), which can be obtained via the thermal treatment of transition-metal macrocycles (TMMs). However, the N4-chelate complex with metal atom (M-N4) moieties as major activity site for ORR are easily destroyed to form inorganic metal species during simple pyrolysis of TMMs. In this report, polyacrylonitrile (PAN) nanofibers were prepared by electrospinning containing a small amount of hemin (chloroprotoporphyrin IX iron(III), TMMs). The electrospun nanofibers were converted into Fe, N co-doped carbon nanofibers (Fe-N-CNFs) through preoxidized and thermal treatment. The PAN macromolecules can prevent hemin from aggregation during the process of pyrolysis. The Fe elemental mapping demonstrated that Fe species probably existed in a single atom state. The Fe K-edge X-ray absorption fine structure spectrum of Fe-N-CNFs proved that the Fe-N4 moieties have been successfully reserved. The X-ray photoelectron spectra of Fe-N-CNFs indicated that the amount of Fe-N4 moieties increased with the increased percent of hemin. Therefore, the Fe-N-CNFs exhibited the higher catalytic activity for ORR compared with Pt electrocatalysts. Furthermore, the Fe1-N-CNFs displayed higher stability and methanol tolerance than Pt/C.

Ternary NiFeZr layered double hydroxides: a highly efficient catalyst for the oxygen evolution reaction.

Transition metal layered double hydroxides (LDHs) have attracted wide public attention as highly promising non-precious metal electrocatalysts. Herein a ternary NiFeZr LDH was reported with excellent OER catalytic activity, benefiting from the rapid charge transfer caused by the synergistic effect of the doping of Zr and three-dimensional nanosheet structures.

Co2B and Co Nanoparticles Immobilized on the N-B-Doped Carbon Derived from Nano-B4C for Efficient Catalysis of Oxygen Evolution, Hydrogen Evolution, and Oxygen Reduction Reactions.

A novel hybrid electrocatalyst of Co2B and Co nanoparticles immobilized on N-B-doped carbon derived from nano-B4C (Co2B/Co/N-B-C/B4C) is in situ synthesized by pyrolysis of nano-B4C supporting Co(OH)2 nanoparticles with melamine. The Co2B and Co nanoparticles are formed and anchored on the generated N and B codoped carbon and undecomposed B4C. The hybrid exhibits remarkable catalytic performances toward the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR)-a very small potential of 1.53 V at 10 mA cm-2 for the OER and a high catalytic kinetics and superior durability for the ORR-which are superior to the RuO2 and Pt/C catalyst, respectively. Most impressively, the hybrid delivers a very small potential gap of 710 mV, which is lower than those of most bifunctional electrocatalysts reported. In addition, the hybrid also shows a satisfying hydrogen evolution reaction performance offering a small overpotential of 220 mV at 10 mA cm-2 and wonderful stability. The excellent trifunctional catalytic performances issue from synergetic effects of Co2B, metal Co, Co/N-doped carbon, and B self-doped carbon coexisting in the hybrid with good interaction mutually. This work provides a new-type efficient multifunctional catalyst for regenerative fuel cell and overall water-splitting technologies.

Tungsten-coated nano-boron carbide as a non-noble metal bifunctional electrocatalyst for oxygen evolution and hydrogen evolution reactions in alkaline media.

Herein, tungsten-coated nano-boron carbide (W-WB4-WCx/B4C) particles were prepared by heating a mixture of B4C and W powder using a spark plasma coating (SPC) method. During the discharge treatment process, metal W in the mixture is activated and reacts with B4C to form WCx, WB4, and graphite nanoribbons. The oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) performance of W-WB4-WCx/B4C is tested in an alkaline solution, and the results show that the W-WB4-WCx/B4C composite electrocatalyst exhibits a low overpotential of 0.36 V at 10 mA cm-2 for the OER, a small overpotential of -0.19 V (j = 10 mA cm-2) for the HER, as well as good stability. The significantly enhanced electrocatalytic performance of the W-WB4-WCx/B4C composites is attributed to their unique structure, in which WCx and WB4 not only improve the catalytic activity for the OER and HER, but also effectively anchor the W coating on the substrate.

Preparation and Characterization of Zirconia-Coated Nanodiamonds as a Pt Catalyst Support for Methanol Electro-Oxidation.

Zirconia-coated nanodiamond (ZrO2/ND) electrode material was successfully prepared by one-step isothermal hydrolyzing from ND-dispersed ZrOCl2·8H2O aqueous solution. High-resolution transmission electron microscopy reveals that a highly conformal and uniform ZrO2 shell was deposited on NDs by this simple method. The coating obtained at 90 °C without further calcination was mainly composed of monoclinic nanocrystalline ZrO2 rather than common amorphous Zr(OH)4 clusters. The ZrO2/NDs and pristine ND powder were decorated with platinum (Pt) nanoparticles by electrodeposition from 5 mM chloroplatinic acid solution. The electrochemical studies indicate that Pt/ZrO2/ND catalysts have higher electrocatalytic activity and better stability for methanol oxidation than Pt/ND catalysts in acid.

Inhibiting the oxidation of diamond during preparing the vitrified dental grinding tools by depositing a ZnO coating using direct urea precipitation method.

Oxidation of diamond during the manufacturing of vitrified dental grinding tools would reduce the strength and sharpness of tools. Zinc oxide (ZnO) coating was deposited on diamond particles by urea precipitation method to protect diamond in borosilicate glass. The FESEM results showed that the ZnO coating was formed by plate-shaped particles. According to the TG results, the onset oxidation temperature of the ZnO-coated diamond was about 70 °C higher than the pristine diamond. The EDS results showed that ZnO diffused into the borosilicate glass during sintering. As the result, the bending strength of the composites containing ZnO-coated diamond was increased by 24% compared to that of the composites containing pristine diamond.

A hybrid of titanium nitride and nitrogen-doped amorphous carbon supported on SiC as a noble metal-free electrocatalyst for oxygen reduction reaction.

A novel noble metal-free catalyst, with nitrogen-doped amorphous carbon and titanium nitride particles supported on SiC (NC-TiN/SiC), was synthesized. The NC-TiN/SiC catalyst exhibited excellent oxygen reduction reaction activities as well as superior stability and methanol tolerance. The catalytic activities were attributed to the synergistic effect of TiN and NC.

Redox properties of undoped 5 nm diamond nanoparticles.

This paper demonstrates the promoting effects of 5 nm undoped detonation diamond nanoparticles on redox reactions in solution. An enhancement in faradaic current for the redox couples Ru(NH(3))(6)(3+/2+) and Fe(CN)(6)(4-/3-) was observed for a gold electrode modified with a drop-coated layer of nanodiamond (ND), in comparison to the bare gold electrode. The ND layer was also found to promote oxygen reduction. Surface modification of the ND powders by heating in air or in a hydrogen flow resulted in oxygenated and hydrogenated forms of the ND, respectively. Oxygenated ND was found to exhibit the greatest electrochemical activity and hydrogenated ND the least. Differential pulse voltammetry of electrode-immobilised ND layers in the absence of solution redox species revealed oxidation and reduction peaks that could be attributed to direct electron transfer (ET) reactions of the ND particles themselves. It is hypothesised that ND consists of an insulating sp(3) diamond core with a surface that has significant delocalised pi character due to unsatisfied surface atoms and C[double bond, length as m-dash]O bond formation. At the nanoscale surface properties of the particles dominate over those of the bulk, allowing ET to occur between these essentially insulating particles and a redox species in solution or an underlying electrode. We speculate that reversible reduction of the ND may occur via electron injection into available surface states at well-defined reduction potentials and allow the ND particles to act as a source and sink of electrons for the promotion of solution redox reactions.