Amorphous/Crystalline Heterojunction Ni(OH)₂/Cu₂O(111) for Photoelectrocatalysis NO₃ ^--to-NH₃: Positive Onset...

Area of Science:

• Materials Science
• Electrochemistry
• Environmental Science

Background:

• Nitrate (NO₃^-) reduction to ammonia (NH₃) is crucial for the nitrogen cycle but faces challenges with traditional methods.
• Standalone electrocatalysis and photocatalysis have limitations in efficiency and selectivity for nitrate conversion.
• Developing advanced photoelectrocatalysts is key to overcoming these limitations for sustainable NH₃ synthesis.

Purpose of the Study:

• To construct an efficient amorphous/crystalline heterojunction Ni(OH)₂/Cu₂O photoelectrocatalyst.
• To achieve synergistic photoelectrocatalysis (SPEC) for enhanced NH₃ synthesis from NO₃^- reduction.
• To investigate the mechanism of the heterojunction in accelerating the reaction and improving selectivity.

Main Methods:

• Fabrication of a Ni(OH)₂/Cu₂O heterojunction via photoelectrocatalytic interface regulation.
• Characterization of light absorption and charge separation efficiencies.
• In situ experiments to elucidate the roles of crystalline Cu₂O and amorphous Ni(OH)₂ in the catalytic process.
• Testing the catalyst's performance in simulated fertilizer plant wastewater.

Main Results:

• Achieved ∼100% light absorption and ∼90% charge separation efficiency.
• Demonstrated rapid 98.80% NO₃^- conversion with >97% NH₃ selectivity and >99% Faradaic efficiency (FE).
• Attained a high NH₃ yield of 1316.1 µmol h^-1 cm^-2 with a low onset potential of 0.322 V vs RHE.
• Successfully applied to fertilizer plant wastewater, achieving ∼90% NO₃^- removal and >85% NH₃ selectivity.

Conclusions:

• The Ni(OH)₂/Cu₂O heterojunction enables efficient and selective photoelectrocatalytic NO₃^- reduction to NH₃ via synergistic effects.
• The catalyst demonstrates significant potential for environmental remediation and sustainable ammonia production.
• The study highlights the importance of interface engineering in designing advanced photoelectrocatalytic systems.