Synergistic dual active sites in metal-organic framework-on-metal hydroxide heterostructures for enhanced...

The electrocatalytic nitrate reduction reaction (NO₃RR) plays a vital role in sustainable ammonia (NH₃) production and environmental restoration. Although some metal-organic frameworks (MOFs) have shown promise as electrocatalysts for NO₃RR, their current performance is limited, highlighting the need for innovative design strategies to improve their efficiency. In this study, a MOF-on-metal hydroxide heterostructured electrocatalyst with interfacial dual active sites is designed to optimize NO₃RR for NH₃ production. The electrocatalyst is synthesized by growing the MOF cobalt(II)-coordinated 4-(2,4,5-tripyridin-4-ylphenyl)pyridine) (or Co-TEPB) nanosheets around Fe-doped cobalt fluorohydroxide (or Fe-Co(OH)F) nanowires. Our theoretical and experimental studies reveal that integrating the MOF with the metal hydroxide leads to electronic coupling between Fe-Co(OH)F and Co-TEPB at the interface. While the Fe sites facilitate the adsorption and activation of NO₃^-, and the Co sites in Fe-Co(OH)F promote H₂O decomposition, providing active surface-adsorbed hydrogen (H_ads) species for the hydrogenation of nitrogen-containing intermediates on adjacent Fe sites. This synergistic process effectively reduces the energy barriers involved in the NO₃RR. Additionally, the engineered heterointerface accelerates electron transfer, resulting in exceptional NO₃RR performance that yields NH₃ at a rate of 22.45 ± 0.48 mg h^-1 cm^-2 and with a Faradaic efficiency of 99.63 ± 0.34 %, both of which surpass those of most reported MOF-based electrocatalysts. These findings provide valuable insights into the design of high-performance NO₃RR electrocatalysts, advancing the field toward more efficient and sustainable solutions for NH₃ production and environmental remediation.