HER Catalytic Activity Research Articles

Modulating the surface segregation of PdCuRu nanocrystals for enhanced all-pH hydrogen evolution electrocatalysis

Core–shell PdCuRu trimetallic nanocrystals with a Pd-rich shell can be obtained by leveraging controlled surface segregation, and high-performance HER catalytic activity finally was achieved at all pH values.

Soft magnetic Fe5C2-Fe3C@C as an electrocatalyst for the hydrogen evolution reaction.

Herein, cubic iron carbides encapsulated in an N-doped carbon shell (ICs@NC) were prepared by a simple two-step method. The two-step method included the preparation of iron oxalate dihydrate and the process of calcination with ethylenediamine. By changing the calcination temperature, we could control the type of iron carbide formed. Moreover, the prepared iron carbide@N-doped carbon core-shell particles exhibited regular cubic shapes and soft magnetic properties with high saturation magnetization. More importantly, we investigated the electrocatalytic activity of the iron carbide@N-doped carbon catalysts for the hydrogen evolution reaction (HER). The results show that the Fe5C2-Fe3C@NC catalyst has efficient HER catalytic activity with an overpotential of 209 mV@10 mA cm-2.

Component-controllable cobalt telluride nanoparticles encapsulated in nitrogen-doped carbon frameworks for efficient hydrogen evolution in alkaline conditions

Rational structure design and component-controlled synthesis are attractive and challenging methods to develop materials with unique function for renewable energy conversion such as hydrogen production via water splitting. The earth-abundant and affordable transition metals have been regarded as ideal alternatives to precious platinum. Herein, we report the designed synthesis of component-modified cobalt telluride nanoparticles encapsulated in the nitrogen-doped carbon frameworks with the feature of high surface area and great electron conductivity. Compared with CoTe2/C and CoTe/C, the Co1.11Te2/C presents the highest catalytic activity for HER in 1M KOH due to its structural and component advantages. After a continuous reaction for 20 h or cycling for 1000 cycles, Co1.11Te2/C shows only a little performance loss. This work provides an effective approach to synthesize low-cost and efficient electrocatalysts for HER via rational structural and component design.

Tungsten carbide electrocatalysts prepared from metallic tungsten nanoparticles for efficient hydrogen evolution

Pyrolysis of hexacarbonyl tungsten, W(CO)6, in 1-octadecene has been used to prepare colloidal tungsten, W, nanoparticles (NPs). The obtained W NPs has been spin-coated on graphite (C) electrodes. Heat treatment of the W/C electrodes at elevated temperatures (≥900 °C) allows the preparation of metallic W and tungsten carbide (W2C@WC) thin films. The obtained W2C@WC electrodes were used for hydrogen evolution studies (HER) in 0.5 M H2SO4. Cyclic voltammetry tests for 1000 cycles showed that W2C@WC exhibit long term stability without significant drop in current density. The overpotential defined at 10 mA/cm2 is 310 mV vs. RHE giving an excellent catalytic activity for HER. Materials characterization has been achieved using transmission electron microscopy (TEM), scanning electron microscopy (SEM), and electrochemical impedance spectroscopy (EIS). Here, EIS studies were used to access the charge-transfer resistance of tungsten carbide electrodes.

Transformation from graphitic C3N4 to nitrogen-boron-carbon ternary nanosheets as efficient metal-free bifunctional electrocatalyst for oxygen reduction reaction and hydrogen evolution reaction

A novel type of Nitrogen-Boron-Carbon ternary nanosheets (NBCs) was prepared directly from graphitic-phase carbon nitride (g-C3N4) and achieved high yields. In these NBCs, the molar content of nitrogen and boron can exceed that of carbon, at the same time with good electronic conductivity. It was observed that there is a coexistence tendency for B/N two elements which was able to maintain the aromaticity of micro-regions. The Morphology analysis, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Raman spectrum results point to a two-dimensional conjugated dominated structure. In addition, NBCs exhibited superior electrochemical performance for ORR with much better methanol tolerance and catalytic stability than commercial Pt/C catalyst. NBCs also showed excellent catalytic activity for HER in aqueous solutions over a wide range of pH values, including acidic, neutral and alkaline conditions. These ternary nanosheets of such high N and B content has not been previously reported and potentially open up a broad research and application prospects.

Protected Metallic MoS2 Nanosheets Outlast Pristine Metallic MoS2 Nanosheets for Hydrogen Evolution Reaction

Functionalizing nanosheets of metallic molybdenum disulfide (MoS2) provides a synthetic chemical route for controlling the electronic properties and stability within the traditionally thermally unstable metallic state. Metallic MoS2 nanosheets have been studied for HER due to their higher reactivity for HER, earth abundance, low-cost, and non-toxicity, which makes metallic MoS2 a candidate to replace platinum for HER. The functionalized nanosheets are more stable to the thermally initiated phase transformation from the metallic 1T phase to the semiconducting 2H phase. Furthermore, we show for an exemplary functionalized sample (Et2NPh-MoS2) that functionalization leads to better stability and long-term performance under HER conditions. These results provide a framework for understanding and controlling the balance between catalytic activity and stability for these unique 2D materials. Chemically-exfoliated, metallic (1T) MoS2 nanosheets are functionalized with organic phenyl rings containing electron donating or withdrawing groups. We find that MoS2 functionalized with the most electron donating functional group (p-(CH3CH2)2NPh-MoS2) is the most efficient catalyst for HER in this series, with initial activity similar to the pristine metallic phase of MoS­­­­­­ 2. The p-(CH3CH2)2NPh-MoS2 is more stable than unfunctionalized metallic MoS2 and outperforms unfunctionalized metallic MoS2 for continuous H2 evolution within 10 min under the same conditions. With regards to the entire studied series, the overpotential and Tafel slope for catalytic HER are both directly correlated with the electron donating strength of the pendant group on the phenyl ring. The results are consistent with a mechanism involving ground-state electron donation or withdrawal to/from the MoS2 nanosheets, which modifies the electron transfer kinetics and catalytic activity of the MoS2 sheet. We show that the functional groups preserve the metallic feature of the MoS2 films, inhibiting conversion to the thermodynamically stable semiconducting state (2H) when annealed at 150 °C for 24 h in a nitrogen atmosphere. We propose that this protection is critical to maintaining the catalytically active state of 1T MoS2 nanosheets. Our results demonstrate a strong correlation between the electron donating strength of substituents and the surface energetics, electron transfer resistance, and the HER catalytic activity of functionalized MoS2 nanosheets.

Engineering Ultrathin C3N4 Quantum Dots on Graphene as a Metal-Free Water Reduction Electrocatalyst

Developing an efficient electrocatalyst with the desired architectural and electronic properties is paramount for water splitting. Here, we apply theoretical calculations to experimental studies to uncover the influence of structure engineering (quantizing and support coupling) on the HER catalytic activity and develop an optimized C3N4 hybrid catalyst. Impressively, the desired atom-thick C3N4 quantum dots on graphene (CNQDs@G) has been successfully obtained and achieves HER performance with low overpotential (110 mV) at 10 mA cm–2, large exchange current density (3.67 μA cm–2), and long-term durability, better than those of many metallic catalysts. In combination with the experimental results, DFT calculations also disclose that the HER catalytic activity of CNQDs@G originates from bisynergetic effects: one between G and CNQDs and another between the edge pyridinic-N sites and the molecular sieve structure.

1T@2H-MoSe2 nanosheets directly arrayed on Ti plate: An efficient electrocatalytic electrode for hydrogen evolution reaction

Few-layered MoSe2 nanosheets with mixed 1T/2H phase were successfully arrayed on a Ti substrate (forming 1T@2H-MoSe2/Ti) through a facile one-step solvothermal process. After testing different synthesis conditions, it was found that the optimal process involves a temperature of 200 °C and a reaction time of 12 h. Structural characterizations reveal that the morphology of 1T@2H-MoSe2 consists of edge-terminated nanosheets with one to five layers, composed of a mixed 1T/2H phase dominated by the 1T one. The 1T@2H-MoSe2/Ti electrode shows excellent HER catalytic activity, with a small onset potential (−120 mV vs. reversible hydrogen electrode, RHE) and an electrode potential of only −133 mV (vs. RHE) to achieve a current density of 20 mA·cm−2. This excellent electrocatalytic activity is due to the synergistic effects of 1T metallic phase, few-layered nanosheet morphology, and direct growth of 1T@2H-MoSe2on the Ti substrate. In addition, the 1T@2H-MoSe2/Ti electrode shows excellent stability towards long-term electrolysis. This is due to the long-term stability of the valence states of Mo and Se, as shown by post-electrolysis X-ray photoelectron spectroscopy analysis.

Pd surface functionalization of 3D electroformed Ni and Ni-Mo alloy metallic nanofoams for hydrogen production

The paper presents some experimental results regarding the functionalization of 3D electroformed Ni and Ni-Mo alloy nanofoams with Pd nanoclusters, as potential cathodic materials suitable for HER during seawater electrolysis. The electrodeposition from aqueous electrolytes containing NiCl2 and NH4Cl has been applied to prepare the 3D Ni nanofoams. Ni-Mo alloys have been electrodeposited involving aqueous ammonium citrate type electrolytes. Pd surface functionalization has been performed using both electroless and electrochemical procedures. Pd content varied in the range of 0.5 – 8 wt.%, depending on the applied procedure and the operation conditions. The use of a porous structure associated with alloying element (i.e. Mo) and Pd surface functionalization facilitated enhanced performances from HER view point in seawater electrolyte (lower Tafel slopes). The determined Tafel slope values ranged from 123 to 105 mV.dec-1, suggesting the Volmer step as rate determining step. The improvement of the HER catalytic activity may be ascribed to a synergistic effect between the high real active area of the 3D electroformed metallic substrate, Ni alloying with a left transition metal and surface modification using Pd noble metal.

A theoretical study on the surface and interfacial properties of Ni3P for the hydrogen evolution reaction

DFT study on the catalytic activity for HER on low-index Ni3P crystal surfaces.

A nanoporous metal phosphide catalyst for bifunctional water splitting

Nanoporous Ni–Fe–P prepared by dealloying exhibits excellent bifunctional catalytic activity for HER and OER under alkaline conditions.

Theoretical insights into the effective hydrogen evolution on Cu3P and its evident improvement by surface-doped Ni atoms.

On the basis of the first-principles DFT computations, we have systematically investigated the structures and hydrogen evolution reaction (HER) catalytic activities for pristine and Ni-doped Cu3P systems. It was revealed that the (11[combining macron]0) surface could be the one with the most exposure for the Cu3P structure. The calculated free energy values of H* (ΔGH*) are in the range from 0.012 to 0.320 eV, reflecting the HER activity on the (11[combining macron]0) surface, which is consistent with the experimentally reported results. Our computed results also reveal that the top sites over P atoms as well as the bridge and hollow sites composed of Cu atoms can make the main contribution to the HER activity on the (11[combining macron]0) surface, and the hollow sites (ΔGH* ≈ 0 eV) can serve as the most active sites due to the considerably flexible structural features. Furthermore, we have proposed an effective strategy through doping Ni to significantly improve the HER catalytic activity on the (11[combining macron]0) surface by effectively optimizing the adsorption state of H* based on the case that Ni and Cu have the opposite ability to bind with H. All these doped systems can uniformly possess high HER activity, and particularly some doped structures with the appropriate Ni-atom number can even exhibit considerably high HER activity over a wide range of H coverage, indicating the more excellent catalytic performance. It is worth mentioning that the surface-metal-atoms for these Ni-doped systems can still exhibit flexible behavior, which can also be beneficial for realizing high HER activity. These fascinating theoretical insights at the atomic level can be advantageous for achieving highly efficient non-precious HER electrocatalysts based on copper phosphide and even other transition metal phosphides in the near future.

Ultrasmall Ru2P nanoparticles on graphene: a highly efficient hydrogen evolution reaction electrocatalyst in both acidic and alkaline media.

Ultrasmall ruthenium phosphide nanoparticles grown on reduced graphene oxide nanosheets (Ru2P/RGO-20) are reported as a highly efficient hydrogen evolution reaction (HER) catalyst. It achieves a current density of -10 mA cm-2 at extremely low overpotentials of -22 and -13 mV under acidic and alkaline conditions, respectively, superior to those of commercial Pt/C.

Fabrication of strong bifunctional electrocatalytically active hybrid Cu–Cu2O nanoparticles in a carbon matrix

Earth-abundant copper-based hybrid Cu–Cu2ONPs@C in the carbon matrix exhibited enhanced OER and HER catalytic activity compared to pure Cu2O and CuNPs@C.

Nickel telluride as a bifunctional electrocatalyst for efficient water splitting in alkaline medium

Ni3Te2 has been reported as a highly efficient OER electrocatalyst with an overpotential of 180 mV at 10 mA cm−2 and also showing HER catalytic activity in alkaline medium.

Improving the electrocatalytic activity for hydrogen evolution reaction by lowering the electrochemical impedance of RuO2/Ni-P

In this paper Ni-P, RuO2 and RuO2/Ni-P composites were deposited on Ni plates through pulsed electrodeposition method, and their activities for HER in alkaline solution were studied comparatively. Scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) analysis confirmed the formation of every composite. The electrochemical impedance spectroscopy (EIS) showed that Ni-P/Ni had lower charge transfer resistance at high overpotential and higher charge transfer resistance at low overpotential than RuO2/Ni. While Ni-P/Ni exhibited lower catalytic activity for HER at low overpotential and higher catalytic activity at high overpotential than RuO2/Ni. Meanwhile, RuO2/Ni-P/Ni had the lowest charge transfer resistance and highest catalytic activity among the three electrodes at both low and high overpotentials. It indicated that RuO2/Ni-P/Ni with less Ni-P and RuO2 exhibited enhanced catalytic activity for HER than both RuO2/Ni and Ni-P/Ni, due to an electron charge transfer synergistic effect of RuO2 and Ni-P.

Bimetallic iron cobalt oxide self-supported on Ni-Foam: An efficient bifunctional electrocatalyst for oxygen and hydrogen evolution reaction

Water electrolysis offers an efficient way to store energy derived from renewable sources in the form of hydrogen. However, the practical implication of this technology is hindered by the lack of efficient earth abundant catalyst capable of accelerating both half reaction of water electrolysis. In this regards, herein; we have prepared a highly active composite electrode by depositing hierarchical spinel iron cobalt oxide on the surface of nickel foam. The layered morphology of iron cobalt oxide is ideal for effective transfer of electrolyte and facile dissipation of gaseous product. Moreover, intimate contact between the catalyst and the current collector caused a significant reduction in charge transfer resistance. Consequently, composite electrode displayed enhanced catalytic activity for HER and OER, achieving the benchmark current density of 10mAcm−2 at a low overpotential of 205mV and 244mV respectively. In addition, a two-electrode alkaline water electrolyzer constructed by employing the composite electrode as anode and cathode yielded a current density of 10mAcm−2 at an applied potential of only 1.62V. The long-lasting stability of iron cobalt oxide-Ni foam electrode along with its exceptional catalytic activity makes it a promising alternative to substitute the precious metal catalyst used in commercial water electrolyzer.

Facile electrodeposition of cauliflower-like S-doped nickel microsphere films as highly active catalysts for electrochemical hydrogen evolution

Self-supported cauliflower-like S-doped Ni microspheres grown on a Cu wire (NiSx/CW) are fabricated via a facile, one-step electrodeposition approach in ethaline, which exhibit highly active and durable HER catalytic activity in alkaline solution.

Nano-structured hybrid molybdenum carbides/nitrides generated in situ for HER applications

A highly efficient, low-cost (precious-metal-free), highly stable nanohybrid electrocatalyst containing carbon-supported molybdenum carbide and nitride nanoparticles of size ranging from 8 to 12 nm exhibit excellent HER catalytic activity.

Synthesis of MoS2(1−x)Se2x and WS2(1−x)Se2x alloys for enhanced hydrogen evolution reaction performance

An excellent HER catalytic activity confirmed with overpotentials of 141 mV (MoS2(1−x)Se2x) and 167 mV (WS2(1−x)Se2x) at 10 mA·cm−2.