One-step construction of a transition-metal surface decorated with metal sulfide nanoparticles: A high-efficiency electrocatalyst for hydrogen generation

Corrosion-resistant titanium-based electrodes synergistically stabilized with polymer for hydrogen evolution reaction

The economic and reasonable design of highly stable and corrosion-resistant electrodes is fundamental to achieving the industrial-scale hydrogen productions via water electrolysis, but electrodes' premature failures are often caused by corrosion and stress damage. Therefore, these challenges are successfully solved by utilizing conductive and crack-resistant polyaniline "stabilizer" with a mild chemical plating process to construct the catalytic electrode on a titanium substrate (15 %PANI-NiB@Ti) in the present work. The 15 %PANI-NiB@Ti catalytic electrodes have been in continuous operation for 350 h at the current density of 200 mA cm-2 with the high efficiency of 98.4 % in a 323.15 K environment. With the high economy and universality, the catalytic electrodes have good catalytic performance and reliability in the extreme industrial environments, such as high temperature, air, and high current density. Except for the above advantages, the 15 %PANI-NiB@Ti catalytic electrodes also have good cracking resistance, which provides a novel and feasible approach to the industrial application of transition metal catalytic electrodes.

Recent Advancements in Ascribing Several Platinum Free Electrocatalysts Pertinent to Hydrogen Evolution from Water Reduction

The advancement of a sustainable and scalable catalyst for hydrogen production is crucial for the future of the hydrogen economy. Electrochemical water splitting stands out as a promising pathway for sustainable hydrogen production. However, the development of Pt-free electrocatalysts that match the energy efficiency of Pt while remaining economical poses a significant challenge. This review addresses this challenge by highlighting latest breakthroughs in Pt-free catalysts for the hydrogen evolution reaction (HER). Specifically, we delve into the catalytic performance of various transition metal phosphides, metal carbides, metal sulphides, and metal nitrides toward HER. Our discussion emphasizes strategies for enhancing catalytic performance and explores the relationship between structural composition and the performance of different electrocatalysts. Through this comprehensive review, we aim to provide insights into the ongoing efforts to overcome barriers to scalable hydrogen production and pave the way for a sustainable hydrogen economy.

A sulfur defective Mn-doped Ni3S2-xnanosheet for enhanced overall water splitting

Non-precious and stable electrocatalysts towards both oxygen and hydrogen evolution reaction (OER/HER) are essential for effective overall water splitting in alkaline solution. In this study, a sulfur defective and manganese-doped nickel sulfide nanosheet that uniformly grown on nickel foam substrate (Mn-Ni₃S_2-x@NF) is synthesized. In alkaline solution, the Mn-Ni₃S_2-x@NF showed a low overpotential of 76 and 110 mV for OER and HER at 10 mA cm^-2, respectively, together exhibiting excellent stability for both OER and HER reaction. It was confirmed by the experimental results that sulfur defects and Mn-doping synergistically optimized the electronic structure of Mn-Ni₃S_2-xwith increased electrical conductivity and enhanced OER/HER activity. Moreover, amorphous nickel oxyhydroxide (NiOOH) was observed byin situRaman during the OER condition, suggesting NiOOH is the active phase for OER reaction. Furthermore, the electrolyzer assembled by Mn-Ni₃S_2-x@NF merely needs 1.46 V to reach 10 mA cm^-2and shows good stability as well. This study provides a feasible way to prepare high-efficiency bifunctional catalysts for overall water splitting.

Synthesis of Self-Supported Cu/Cu3P Nanoarrays as an Efficient Electrocatalyst for the Hydrogen Evolution Reaction

Owing to the energy crisis and environmental pollution, it is essential to develop cheap, environmentally friendly and sustainable energy to replace noble metal electrocatalysts for use in the hydrogen evolution reaction (HER). We report herein that a Cu/Cu3P nanoarray catalyst was directly grown on the surfaces of Cu nanosheets from its Cu/CuO nanoarray precursor by a low-temperature phosphidation process. In particular, the effects of phosphating distance, mass ratio and temperature on the morphology of Cu/Cu3P nanoarrays were studied in detail. This nanoarray, as an electrocatalyst, displays excellent catalytic performance and long-term stability in an acid solution for electrochemical hydrogen generation. Specifically, the Cu/Cu3P nanoarray-270 exhibits a low onset overpotential (96 mV) and a small Tafel slope (131 mV dec−1).

Nickel sulfide nanorods decorated on graphene as advanced hydrogen evolution electrocatalysts in acidic and alkaline media

Nowadays, the fabrication of robust and earth-abundant hydrogen evolution electrocatalysts with noble-metal-like catalytic activities is still facing great challenges. In this report, nanorod (NR)-shaped nickel sulfide (NiS) is successfully decorated on graphene (Gr) by utilizing carbon cloth (CC) as a substrate (NiS-Gr-CC). Benefiting from the NR morphology and strong interfacial synergetic effect between NiS and Gr, the NiS-Gr-CC electrocatalyst shows good catalytic activity for hydrogen evolution reaction (HER). Specifically, the low Tafel slopes of 46 and 56 mV dec^-1 along with the small overpotentials of 66 and 71 mV at 10 mA cm^-2 are obtained in the acidic and alkaline electrolytes, respectively. Density functional theory results indicate that the combination of NiS and Gr can optimize the adsorption energy of H* during the HER process. The long-term durability measurement result reveals that our NiS-Gr-CC heterostructure has good electrocatalytic cycling stability (∼80 h) in both acidic and alkaline electrolytes. These results confirm that the NiS-Gr-CC heterostructure is a promising candidate for hydrogen evolution electrocatalyst with high catalytic activity.

Synergistic Electrocatalytic Hydrogen Evolution in Ni/NiS Nanoparticles Wrapped in Multi-Heteroatom-Doped Reduced Graphene Oxide Nanosheets

Hydrogen production is a key driver for sustainable and clean fuels used to generate electricity, which can be achieved through electrochemical splitting of water in alkaline solutions. However, the hydrogen evolution reaction (HER) is kinetically sluggish in alkaline media. Therefore, it has become imperative to develop inexpensive and highly efficient electrocatalysts that can replace the existing expensive and scarce noble-metal-based catalysts. Herein, we report on the rational design of nonprecious heterostructured electrocatalysts comprising a highly conductive face-centered cubic nickel metal, a nickel sulfide (NiS) phase, and a reduced graphene oxide (rGO) doped with phosphorous (P), sulfur (S), and nitrogen (N) in one ordered heteromaterial named Ni/NiS/P,N,S-rGO. The Ni/NiS/P,N,S-rGO electrode shows the best performance toward HER in 1.0 M KOH media among all materials tested with an overpotential of 155 mV at 10.0 mA cm^-2 and a Tafel slope of 135 mV dec^-1. The performance is comparable to the herein used Pt/C-20% benchmark catalyst examined under the same experimental conditions. The chronoamperometry and chronopotentiometry measurements have reflected the high durability of the Ni/NiS/P,N,S-rGO electrode for technological applications. At the same time, the current catalyst showed a high robustness and structure retention after long-term HER performance, which is reflected by SEM, XRD, and XPS measurements.

Novel Aggregation-Induced Emission Materials/Cadmium Sulfide Composite Photocatalyst for Efficient Hydrogen Evolution in Absence of Sacrificial Reagent

This work focuses on the development of a novel organic–inorganic photoactive material composited by aggregation-induced emission luminogens (AIE) and CdS. Tetraphenylethene-based AIE (TPE-Ca) is synthesized on CdS to form CdS/TPE-Ca electrode, due to its suitable band structure and potential capability of renewable energy production. The CdS/TPE-Ca electrode presents over three-fold improved photocurrent density and dramatically reduced interfacial resistance, compared with the pure CdS electrode. In addition, the engineering of the band alignment allows the holes to accumulate on the valance band of TPE-Ca, which would partially prevent the CdS from photo-corrosion, thus improving the stability of the sacrificial-free electrolyte photoelectrochemical cell.

Potentiostatic electrodeposition of Ni-Se-Cu on nickel foam as an electrocatalyst for hydrogen evolution reaction

Development of cost-effective and efficient earth-abundant catalysts for hydrogen evolution reaction (HER) is a great challenge. In this study, by one-step potentiostatic electrodeposition, the Ni-Se-Cu electrocatalyst on nickel foam was fabricated as a binder-free HER electrocatalyst. As compared with Ni-Se electrocatalysts, such fabricated Ni-Se-Cu electrocatalyst exhibited prominent electrocatalytic activity to the HER in alkaline electrolyte. This Ni-Se-Cu electrocatalyst exhibits a small overpotential of 136 mV to achieve a current density of 10 mA·cm^-2 and high electrochemical stability. The remarkable HER properties of Ni-Se-Cu electrocatalyst mainly originate from high electronic conductivity induced by Cu-doping. This work shows a cheap and simple avenue to develop high efficient non-noble electrochemical electrocatalysts for HER.

Deep eutectic solvent-assisted in-situ synthesis of nanosheet-packed Ni3S2 porous spheres on Ni foam for high-performance supercapacitors

Herein, self-supported Ni₃S₂ spherical clusters packed with well-defined nanosheets developed on Ni foam (NF) were rationally fabricated via a novel low-temperature solvothermal sulfurization approach in a choline chloride/ethylene glycol (Ethaline)-based deep eutectic solvent (DES). The DES-based sulfurization process drove an interesting time-dependent surface restructuring and phase transformation that occurred on the Ni substrate, leading to the in-situ formation of a Ni₃S₂ layer with controllable architecture. Pre-deposition of a Ni interlayer on the NF substrate provides more assessable electrochemical surface area and reaction sites, which favored fast crystal nucleation/growth and structural reconstruction. Benefiting from the integrated design and unique 3D interdigital architecture, the optimized Ni₃S₂_5/Ni/NF with a sulfurization time of 5 h exhibits a high specific capacitance (specific capacity) of 5,633 mF cm^-2 (860.6 μAh cm^-2) at a current density of 10 mA cm^-2, and maintains 87.7% of initial specific capacitance after 1,000 charge-discharge process at a current density of 20 mA cm^-2. This facile DES-driven solvothermal sulfurization strategy for the fabrication of integrated metal sulfides-based electrode materials could be promising for practical applications in high-performance electrochemical devices.

Molybdenum Nitride Electrocatalysts for Hydrogen Evolution More Efficient than Platinum/Carbon: Mo2N/CeO2@Nickel Foam

To produce hydrogen economically by electrolysis of water, one needs to develop a non-precious-metal catalyst that is as efficient as platinum metal. Here, we prepare such a catalyst by growing a layer of Mo₂N over a layer of CeO₂ deposited on nickel foam (NF) [hereafter, Mo₂N /CeO₂@NF] and show that the activity of this self-supported catalyst for hydrogen evolution in 1.0 M KOH is more efficient than that of the Pt/C electrode, achieving a current density of 10 mA/cm² at a fairly low overpotential of 26 mV. Furthermore, after a long-time electrochemical stability test for 24 h at a fixed current density, the overpotential needed to attain a current density of 10 mA/cm² is increased only by 6 mV, implying the huge potential of this method to prepare a super HER activity electrode for water splitting.

A one-pot "shielding-to-etching" strategy to synthesize amorphous MoS2 modified CoS/Co0.85Se heterostructured nanotube arrays for boosted energy-saving H2 generation

In this study, a facile one-pot "shielding-to-etching" strategy has been designed for the synthesis of amorphous MoS2 modified CoS/Co0.85Se heterostructured nanotube arrays (a-MoS2/CoS/Co0.85Se HNTs) as a highly efficient electrocatalyst for boosted energy-saving H2 production, using Co(OH)x(CO3)y nanorods as the template. Interestingly, these multi-composition and hollow structured products were achieved in a controllable manner via only a one-pot synthesis, in which the nanorods with shielding layers were firstly obtained and then converted into nanotubes through further etching reaction. Benefiting from the combined nature of multiple-component hollow nanostructures, the electronic structure of the electrocatalyst is efficiently modulated, the electron transfer and ion diffusion pathways are effectively shortened and abundant active sites are created, which leads to excellent activity for urea oxidation and hydrogen evolution reactions with the as-prepared a-MoS2/CoS/Co0.85Se HNTs being employed as the electrodes. As a result, the whole urea electrolysis cell exhibits a driven voltage of only 1.42 V to achieve a current density of 10 mA cm-2, surpassing most reported transition-metal-based electrocatalysts. Moreover, a battery-assisted urea electrolyzer was assembled as well to demonstrate the feasibility of practical less-energy-intensive H2 generation. The method developed in this work is expected to broaden the way of designing and synthesizing multiple-component hollow nanostructures for various applications.