Structural evolution of CrN nanocube electrocatalysts during nitrogen reduction reaction

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Metal nitrides are promising for electrochemical nitrogen reduction reaction (NRR) to synthesize ammonia under ambient conditions.
• Developing efficient, stable, and noble-metal-free electrocatalysts for NRR is crucial for sustainable ammonia production.

Purpose of the Study:

• To investigate templated chromium nitride porous microspheres as a novel electrocatalyst for NRR.
• To evaluate the catalytic performance, stability, and structural evolution of chromium nitride nanocubes (NCs) during NRR.

Main Methods:

• Synthesis of templated chromium nitride porous microspheres composed of nanocubes.
• Electrochemical characterization of the catalyst for NRR performance (NH3 yield and Faradaic efficiency).
• Advanced structural and chemical analysis using STEM, EELS, and EDX to probe catalyst evolution.

Main Results:

• The chromium nitride NCs catalyst demonstrated high stability and an NH3 yield of 31.11 μg h-1 mgcat.-1 with a 16.6% Faradaic efficiency in 0.1 M HCl.
• Physical characterization revealed partial oxidation of the CrN NCs during the reaction.
• STEM-TEM, EELS, and EDX analysis showed an O-rich core and N-rich shell structure in the NCs post-NRR.

Conclusions:

• Templated chromium nitride porous microspheres are efficient noble-metal-free electrocatalysts for NRR.
• The observed gradient nitrogen distribution (N-rich shell) in CrN NCs after NRR is a unique feature contributing to catalyst stability and performance.
• This study highlights the potential of tailored metal nitrides for sustainable ammonia synthesis.