mo doped ni2p nanorings seawater electrolysis hydrogen

Mo-Doped Ni₂P Nanorings Enhance Seawater Electrolysis for Hydrogen Production

The Global Energy Crisis and the Need for Sustainable Hydrogen Production

The increasing reliance on fossil fuels has precipitated a global energy crisis, intensifying environmental pollution and accelerating climate change. A viable pathway toward sustainable energy production involves water electrolysis, wherein renewable electricity facilitates the generation of high-purity hydrogen (H₂) a promising alternative fuel.

Challenges with Seawater Electrolysis

Current hydrogen production technologies predominantly use pure water; however, the limited availability of this resource poses significant challenges. Seawater, with its vast coverage of the Earth's surface, provides an inexhaustible hydrogen source.

Although seawater is abundant, its use in hydrogen production is challenging due to its complex composition, which contains significant concentrations of salts such as chloride, sodium and magnesium.

When utilizing seawater for electrolysis, two primary challenges emerge:

• Unwanted chemical reactions: Chlorine in seawater reacts more readily than oxygen, creating competition that hampers efficiency.
• Electrode degradation: Elevated chloride concentrations accelerate corrosion, diminishing both the system's efficiency and longevity.

Advancements in Seawater Electrolysis Catalysts

Researchers are actively designing advanced catalytic materials to facilitate direct seawater electrolysis. These catalysts aim to optimize oxygen generation while resisting chlorine-induced corrosion, making large-scale hydrogen production more feasible.

The Evolution of Doped-Ni₂P Electrocatalysts

The search for cost-effective alternatives to precious metal catalysts in water splitting is intensifying. Transition metal phosphides (TMPs) have emerged as promising candidates due to their tunable compositions high conductivity and advantageous electronic properties.

Nickel phosphide (Ni₂P) has emerged as a particularly promising transition metal phosphide (TMP). However, TMPs face key challenges, including limited active sites, structural instability during reactions and susceptibility to chlorine-induced degradation (CER poisoning).

Overcoming Challenges with MO-Doped Ni₂P

To overcome these challenges, doping Ni₂P with molybdenum (Mo) has yielded promising improvements. The interaction between Mo and Ni enhances electronic properties, promotes better adsorption of active species and leads to structural enhancements due to lattice distortion. However, the limited surface exposure of Mo-doped Ni₂P remains a key barrier to optimizing its catalytic efficiency for water splitting.

Recent Advancements in Mo-Doped Ni₂P Nanocomposite Design

In light of these challenges our research team under the leadership of Sasanka Deka from the Department of Chemistry at the University of Delhi, has designed an innovative nanocomposite-based electrocatalyst. This catalyst offers both high efficiency and cost-effectiveness for seawater splitting. Our approach involved the development of a torus-shaped Mo-doped Ni₂P nanoparticle (NP) via shape engineering.

Novel Approach for Torus-Shaped Nanoparticles

To accomplish this we employed a novel high-temperature approach aimed at increasing exposure to the (0001) facets. By elevating the concentration of the capping agent and phosphorus precursor at 350°C, we triggered a pronounced Kirkendall effect, promoting outward diffusion and resulting in the formation of torus-shaped particles as the central portion of spherical Ni₂P particles disappeared.

Optimizing Mo-Doped Ni₂P for Direct Seawater Electrolysis

This distinctive morphology provides a greater surface area and an increased density of unsaturated surface atoms compared to traditional spherical particles, as confirmed by surface area-to-volume ratio calculations. This represents the first successful production and application of monodispersed torus-shaped nanoparticles as electrocatalysts for direct seawater electrolysis (SWE).

Achievements and Performance Metrics

Our optimized design introduced novel donut-shaped Mo-doped Ni₂P nanoparticles and achieved one of the lowest cell voltages for overall water splitting (OWS) in direct SWE applications, along with remarkable stability. These findings are published in the journal Small.

When the Mo₀.₁Ni₁.₉P||Mo₀.₁Ni₁.₉P pair serves as bifunctional electrocatalysts for overall water splitting in an alkaline environment, it demands only 1.45 V in 1.0 M KOH and 1.47 V in alkaline seawater at a current density of 10 mA/cm².

Stability and Performance Under Industrial Conditions

The pair also demonstrates excellent stability maintaining consistent performance for more than 80 hours at 400 mA/cm² in alkaline seawater.

As a proof of concept, a video illustrating the direct conversion of solar energy to hydrogen is provided, employing the present electrolyzer and Mo₀.₁Ni₁.₉P||Mo₀.₁Ni₁.₉P pair of electrodes. In this demonstration, a DIY solar panel kit was directly connected to the anode and cathode, where Mo ₀.₁Ni₁.₉P paste was deposited.

A commercially available solar panel (Electronic Spices Solar Panel for DIY, 70 mm x 70 mm) was sourced from Amazon and utilized as a power generator to operate the two-electrode electrolyzer in the video. Credit: The authors 

video

Electrochemical Performance of Mo-Doped Ni₂P Nanorings

Mo-doped Ni₂P nanorings exhibit a significantly improved electrochemical performance for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline electrolytes when compared to undoped Ni₂P and other morphologies.

Key Metrics of Mo₀.₁Ni₁.₉P Catalyst

The optimized Mo₀.₁Ni₁.₉P catalyst demonstrates low overpotentials, favorable Tafel slopes and superior turnover frequencies mass activities and exchange current densities.

With industrially relevant current densities of 500 and 1000 mA/cm² the catalyst operates at record-low voltages of 1.81 and 1.86 V at 25°C and 1.77 and 1.82 V at 75°C for overall alkaline seawater splitting.

Excellent Stability in Harsh Conditions

Furthermore, it exhibits outstanding stability under the challenging conditions of industrial 30 wt% KOH.

Conclusion: Advancements in Mo-Doped Ni₂P Electrocatalysts for Large-Scale Hydrogen Production

In summary, the improvements are attributed to the dual active metal centers and the distinctive ring-shaped structure. The latest synthesis approach introduces a uniquely shaped Mo-doped Ni₂P electrocatalyst, demonstrating considerable potential for large-scale industrial production. Moreover, it provides key insights into the surface chemistry mechanisms at work.

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"Discover the Future of Hydrogen Production with Mo-Doped Ni₂P Nanorings"

The breakthrough in seawater electrolysis with Mo-doped Ni₂P nanorings is reshaping hydrogen production. With unprecedented efficiency and stability, this innovative catalyst is poised to revolutionize renewable energy. Learn more about the science behind this cutting-edge technology and its potential for industrial applications in sustainable hydrogen generation.

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• Earth Day Harsh Reality Blog - Understand the urgent environmental challenges and how innovations like seawater electrolysis are part of the solution.

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