Activating rhodium phosphide-based catalysts for the pH-universal hydrogen evolution reaction.

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Developing highly active and stable platinum-free electrocatalysts is crucial for efficient hydrogen production via water splitting.
• Existing catalysts often face limitations in terms of cost, stability, or activity across diverse pH conditions.

Purpose of the Study:

• To report a novel electrocatalyst composed of rhodium phosphide (Rh2P) nanoparticles encapsulated in N-doped carbon (NC) for the hydrogen evolution reaction (HER).
• To evaluate the catalytic performance and stability of the Rh2P@NC catalyst in various pH environments and compare it with commercial platinum on carbon (Pt/C).
• To elucidate the catalytic mechanism using density functional theory (DFT) calculations.

Main Methods:

• Synthesis of Rh2P nanoparticles coated with an N-doped carbon shell (Rh2P@NC).
• Electrochemical characterization of HER performance, including overpotential measurements at 10 mA cm⁻², in acidic (0.5 M H2SO4), neutral (1.0 M PBS), and basic (1.0 M KOH) media.
• Long-term stability testing of the catalyst.
• Density functional theory (DFT) calculations to investigate the electronic structure and reaction mechanism.

Main Results:

• The Rh2P@NC catalyst exhibited excellent HER activity with low overpotentials: ~9 mV in acid, ~46 mV in neutral, and ~10 mV in base.
• The catalyst demonstrated superior performance and stability compared to commercial Pt/C catalysts across the tested pH range.
• DFT calculations indicated that phosphorus incorporation lowers proton adsorption energy on Rh/NC, facilitating hydrogen generation.
• The synthetic strategy was extended to other transition metal phosphides/N-doped carbon heterostructures, showing broad applicability.

Conclusions:

• The novel Rh2P@NC catalyst offers a highly active and stable platinum-free alternative for hydrogen evolution reaction.
• This catalyst exhibits state-of-the-art performance in acidic and basic media, paving the way for efficient and cost-effective hydrogen production.
• The developed synthetic approach for transition metal phosphide/N-doped carbon heterostructures holds promise for future electrocatalyst design.