Tuning Surface Potential Polarization to Enhance N₂ Affinity for Ammonia Electrosynthesis

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Electrocatalytic nitrogen reduction reaction (NRR) offers a sustainable alternative to the Haber-Bosch process for ammonia synthesis.
• Bismuth tungstate (Bi2WO6) shows promise as an NRR electrocatalyst, but requires activation of its inert basal planes for effective performance.

Purpose of the Study:

• To activate the basal planes of Bi2WO6 for enhanced NRR activity through titanium (Ti) doping.
• To investigate the mechanism of Ti doping on NRR performance using experimental and theoretical methods.

Main Methods:

• Ti doping of Bi2WO6 nanosheets.
• Electrocatalytic performance testing for ammonia synthesis.
• In situ synchrotron radiation-based Fourier transform infrared (SR-FTIR) spectroscopy.
• Density Functional Theory (DFT) calculations.

Main Results:

• Ti doping successfully activated the Bi2WO6 basal planes, enhancing NRR activity.
• Ti doping tuned surface potential, improved N2 adsorption, and weakened the N≡N bond via d(Ti)-p(N) orbital coupling.
• Surface potential polarization facilitated HNN* adsorption on Bi-Ti dual-metal sites.
• Ti-Bi2WO6 nanosheets achieved a Faradaic efficiency of 11.44% and NH3 yield rate of 23.14 µg mg-1 h-1 at -0.2 V vs. RHE with good stability.

Conclusions:

• Ti doping is an effective strategy to activate 2D Bi2WO6 materials for electrocatalytic NRR.
• The study provides insights into the mechanism of NRR on Ti-doped Bi2WO6, aiding the development of advanced electrocatalysts.
• This work demonstrates the synergistic potential of theory and experiment in advancing NRR catalyst design.