Sulfur-Bridge Engineering Enables Reverse Hydrogen Spillover to Atomic Cu for Nitrate-to-Ammonia Electrocatalysis

Area of Science:

• Electrochemistry
• Catalysis
• Materials Science
• Green Chemistry

Background:

• Copper-based catalysts show promise for electrocatalytic nitrate reduction (NO3RR) to ammonia.
• Challenges include nitrite accumulation and insufficient hydrogen supply at high current densities.
• Developing efficient catalysts is crucial for sustainable ammonia synthesis.

Purpose of the Study:

• To design and synthesize a novel catalyst for enhanced electrocatalytic nitrate reduction.
• To investigate the mechanism of hydrogen transfer and its role in accelerating ammonia synthesis.
• To optimize catalyst performance for high yield, selectivity, and durability.

Main Methods:

• Anchoring isolated Cu atoms into a hollow Co3S4 framework (Cu-Co3S4).
• Electrochemical characterization and computational studies to elucidate the catalytic mechanism.
• Tuning Cu site density to balance intermediate adsorption and hydrogen supply.

Main Results:

• The Cu-Co3S4 catalyst features a sulfur-bridged asymmetric active center.
• Co3S4 acts as an efficient hydrogen donor via reverse hydrogen spillover, accelerating nitrogen intermediate hydrogenation.
• Optimized Cu1.01wt%-Co3S4 achieved an NH3 yield rate of 94.52 mg h-1 mgcat.-1 and 95.18% Faradaic efficiency at -0.8 V.
• Exceptional durability (>300 h at -200 mA cm-2) and performance in zinc-nitrate batteries were demonstrated.

Conclusions:

• Coupling intermediate activation with hydrogenation kinetics is vital for high-efficiency NO3RR.
• The sulfur bridge plays a key role in mediating hydrogen transfer.
• This work provides guiding principles for designing advanced electrocatalysts for sustainable ammonia production.