Cuncai Lv

Ni12P5 Nanoparticles as an Efficient Catalyst for Hydrogen Generation via Electrolysis and Photoelectrolysis

The exploitation of a low-cost catalyst is desirable for hydrogen generation from electrolysis or photoelectrolysis. In this study we have demonstrated that nickel phosphide (Ni12P5) nanoparticles have efficient and stable catalytic activity for the hydrogen evolution reaction. The catalytic performance of Ni12P5 nanoparticles is favorably comparable to those of recently reported efficient nonprecious catalysts. The optimal overpotential required for 20 mA/cm(2) current density is 143 ± 3 mV in acidic solution (H2SO4, 0.5 M). The catalytic activity of Ni12P5 is likely to be correlated with the charged natures of Ni and P. Ni12P5 nanoparticles were introduced to silicon nanowires, and the power conversion efficiency of the resulting composite is larger than that of silicon nanowires decorated with platinum particles. This result demonstrates the promising application potential of metal phosphide in photoelectrochemical hydrogen generation.

The hierarchical nanowires array of iron phosphide integrated on a carbon fiber paper as an effective electrocatalyst for hydrogen generation

The development of an effective, non-precious electrocatalyst for the hydrogen evolution reaction (HER) is highly desirable for the commercial application of hydrogen as a clean and renewable energy and remains a substantial challenge. Herein, a hierarchical nanowires array (HNA) of iron phosphide (FeP) nanowires coated with iron phosphide nanorods grown on a carbon fiber paper (CFP) was constructed which exhibited remarkable catalytic activity in the HER. The overpotential required for the current density of 20 mA cm−2 is as small as 45 and 221 mV in acidic and basic solution, respectively, corresponding to Tafel slopes of 53 and 134 mV dec−1. The effective catalytic activity of the CFP–FeP HNA in the HER, together with its long-term stability and nearly 100% faradaic efficiency in water electrolysis, make the CFP–FeP HNA one of the best non-noble electrocatalysts described to date. The prominent catalytic activity of CFP–FeP HNA is correlated to the large number of active sites for the HER, and the fast electron transport from the CFP to the FeP nanorods mediated by FeP nanowires.

Tungsten Sulfide Enhancing Solar-Driven Hydrogen Production from Silicon Nanowires

Tungsten sulfides, including WS2 (crystalline) and WS3 (amorphous), were introduced to silicon nanowires, and both can promote the photoelectrochemical hydrogen production of silicon nanowires. In addition, more enhancement of energy conversion efficiency can be achieved by the loading of WS3, in comparison with loading of WS2. Polarization curves of WS3 and WS2 suggest that WS3 has higher catalytic activity in the hydrogen evolution reaction than WS2, affording higher energy conversion efficiency in silicon nanowires decorated with WS3. The higher electrocatalytic activity of WS3 correlates with the amorphous structure of WS3 and larger surface area of WS3, which result in more active sites in comparison with crystalline WS2.

Graphene Porous Foam Loaded with Molybdenum Carbide Nanoparticulate Electrocatalyst for Effective Hydrogen Generation.

A facile method is developed for the synthesis of graphene porous foam (Gr PF) loaded with dispersed molybdenum carbide (Mo2 C) nanoparticles; the material exhibits effective catalytic activity in the hydrogen evolution reaction (HER). Mo2 C/Gr PF is synthesized by the carbonization of glucose and the carbothermal reduction of hexaammonium molybdate in a confined space defined by the intervals between sodium chloride nanoparticles. The synthesis in the confined space results in thin Gr PF (≈8 nm) loaded with aggregation-free small Mo2 C nanoparticles [(13±2) nm]. The overpotential required for a current density of 20 mA cm(-2) in the electrochemical hydrogen generation is as small as 199 mV in acidic solution and 380 mV in basic solution. The performance is superior to that of a Mo2 C/C composite and compares favorably to those reported for Mo2 C nanostructures. The Mo2 C/Gr PF affords stable water electrolysis in both acidic and basic solution and exhibits nearly 100 % faradaic efficiency. The prominent performance, long-term stability, and high faradic efficiency make Mo2 C/Gr PF a promising HER catalyst for practical hydrogen generation from water electrolysis.

Phase separation synthesis of trinickel monophosphide porous hollow nanospheres for efficient hydrogen evolution

A facile and scalable approach to synthesize trinickel monophosphide (Ni3P) porous hollow nanospheres (PHNs) has been developed, the resultant Ni3P PHNs exhibiting excellent catalytic activity in the hydrogen evolution reaction (HER). The formation of the Ni3P PHNs correlates with phase separation during the thermal annealing of amorphous nickel–phosphorus nanospheres that affords crystalline Ni–Ni3P nanoparticles, and the subsequent selective removal of nickel. The overpotential required for the current density of 20 mA cm−2 is as small as 99 mV in acidic solution. The performance compares favorably with that of other metal phosphides, and is superior to that of transition metal dichalcogenides, carbides, borides, and nitrides. The faradaic efficiency of the Ni3P PHNs is 96%, and the Ni3P PHNs are stable during the long-term electrolysis of water. Density functional theory calculations suggest that a Ni–Ni bridge site and the sites on the top of the P atoms are the active sites during the HER. The scalable production, low cost, excellent catalytic activity, and long-term stability suggest promising application potential for Ni3P PHNs.

Silicon nanowires loaded with iron phosphide for effective solar-driven hydrogen production

Iron phosphide (FeP) was introduced onto silicon nanowires (SiNWs) via precursor loading and phosphorization. The resultant SiNWs/FeP shows remarkably enhanced photoelectrochemical hydrogen production in comparison with bare SiNWs. The solar power conversion efficiency of SiNWs/FeP is as high as 2.64%, which is 94% of that of SiNWs modified with Pt particles, and is larger than those of silicon-based photocathodes loaded with other non-precious electrocatalysts such as transition metals and their chalcogenides. The faster reaction rate of the hydrogen evolution reaction (HER) on the surface of the SiNWs/FeP than that of the bare SiNWs was confirmed by an electrochemistry impedance experiment (EIS). The investigations over the EIS spectra and the flat band potential show that the onset potential of cathodic photocurrent is mainly influenced by the reaction rate of the HER on the surface of the photocathode. The transient photocurrent experiments also suggest the faster kinetics of the HER on the surface of the SiNWs/FeP in comparison with that of the bare SiNWs. This result demonstrates a convenient approach to SiNWs loaded with a highly effective electrocatalyst and its promising application potential in photoelectrochemical hydrogen generation.

Facile synthesis of hollow carbon microspheres embedded with molybdenum carbide nanoparticles as an efficient electrocatalyst for hydrogen generation

In an attempt to exploit efficient and stable non-precious-metal electrocatalysts for hydrogen production from water electrolysis in both acid and basic solution, hollow carbon microspheres embedded with molybdenum carbide nanoparticles are prepared via ultrasonic spray pyrolysis. The as-synthesized catalyst exhibits superior activity in hydrogen evolution reaction (HER) with a small overpotential of 203 mV in acidic solution and 346 mV in basic solution to reach a current density of 20 mA cm−2. The enhanced electrochemical activity should be ascribed to the effects of the anchored structure. The catalyst can work stably in both acidic and basic solution with 100% faradaic efficiency. These excellent properties make the catalyst a promising electrocatalyst in the HER.

Phosphorus doped single wall carbon nanotubes loaded with nanoparticles of iron phosphide and iron carbide for efficient hydrogen evolution

The development of low-cost and high-performance non-precious metal electrocatalysts for the hydrogen evolution reaction (HER) is highly desirable for the wide range of applications of molecular hydrogen as a clean renewable energy source. Here phosphorus doped single wall carbon nanotubes loaded with nanoparticles of iron carbide and iron phosphide are synthesized cost-effectively and time-efficiently using a one-pot and one-step chemical vapor deposition method, and exhibit superb catalytic activity for the HER. The nanohybrid electrocatalyst produces a current density of 20 mA cm−2 at an overpotential of 157 mV in acid solution and 331 mV in basic solution. The Tafel slope is 60.8 mV dec−1 in acid solution and 87.6 mV dec−1 in basic solution. The catalyst can work stably in both acidic and basic solutions with 100% faradaic efficiency. The superb performance correlates with the doping of single wall carbon nanotubes with phosphorus, and the synergistic effect of iron phosphide and iron carbide.

Ultrafast synthesis of molybdenum carbide nanoparticles for efficient hydrogen generation

A facile and ultrafast synthesis of molybdenum carbide coated with few-layer carbon (MoC/C) has been developed, and the effect of reducing the thickness of the carbon coating on its catalytic activity in the hydrogen evolution reaction (HER) has been demonstrated. MoC/C produces a current density of 20 mA cm−2 at an overpotential of 144 mV and a Tafel slope of 63.6 mV dec−1 in 0.5 M H2SO4, and works stably under long-term electrolysis. MoC/C is one of the most active carbide electrocatalysts reported thus far, although MoC is not even the most active phase of molybdenum carbide and MoC/C has a small surface area. Complementary density functional theory calculations have afforded insight into this novel catalyst design, showing that increasing the thickness of the carbon layer leads to the composite system losing the characteristics of MoC and behaving more like a carbon surface, and thereby resulting in a reduction in HER activity.

Self-supported tungsten/tungsten dioxide nanowires array as an efficient electrocatalyst in the hydrogen evolution reaction

In this study, a tungsten/tungsten dioxide (W/WO2) nanowires array (NA) was constructed on a carbon paper (CP) (W/WO2 NA@CP) through the thermal annealing of tungsten trioxide (WO3) NA. W/WO2 NA@CP was proven to be an efficient hydrogen evolution cathode with a strong durability in acidic solutions. W/WO2 NA@CP needs an overpotential of 297 mV to drive a current density of 10 mA cm−2 and 340 mV to drive a current density of 20 mA cm−2. The catalytic activity of W/WO2 NA@CP maintains for at least 50 h in potentiostatic electrolysis. In addition, W/WO2 NA@CP shows nearly a 100% faradaic efficiency during hydrogen generation. The prominent catalytic activity of W/WO2 NA@CP correlates with a large number of active sites for the hydrogen evolution reaction and fast electron transport from the CP to W/WO2 nanowire.