Pulse-Driven Active-Site Switching on Bromine-Modified Cu Enables Sequential 2e^- + 6e^- Nitrate-to-Ammonia Conversion

Area of Science:

• Electrochemistry
• Catalysis
• Materials Science

Background:

• Electrocatalytic nitrate reduction to ammonia (NO3RR) faces challenges due to kinetic mismatches in the 8-electron transfer process.
• Steady active-site electronic states often lead to increased energy consumption and product selectivity issues.

Purpose of the Study:

• To develop a strategy for reversible and self-adaptive regulation of copper active sites for efficient NO3RR.
• To match the distinct reaction kinetics of the (2+6)-electron pathway for NO3RR using pulsed electroreduction electrolysis (PE).

Main Methods:

• Utilized trace-Br-modified Cu/Cu2O catalysts (Br-Cu) with pulsed electroreduction electrolysis (PE).
• Integrated in situ spectroscopy and Density Functional Theory (DFT) calculations for mechanistic investigations.
• Employed a continuous-flow electrochemical cell for long-term electrolysis and ammonia recovery.

Main Results:

• Achieved a reversible and tunable Cuδ+ (0 < δ < 1) state under PE, selectively favoring the 2-electron and 6-electron transfer steps.
• Delivered a 94% Faradaic efficiency for ammonia production.
• Demonstrated high NO3- conversion and NH3 selectivity over 700 hours of continuous operation, with efficient ammonia recovery from aquaculture tailwater.

Conclusions:

• Presented a robust strategy for programmable self-adaptive electronic modulation of catalysts.
• Enabled sustainable ammonia electrosynthesis with high efficiency and selectivity.
• Showcased the potential for practical applications in areas like aquaculture wastewater treatment.