Piezocatalytic nitrate reduction to ammonia in seawater

Renewable energy-driven conversion of nitrate in seawater to ammonia ion (NH4+) is a promising strategy for concurrent marine environmental remediation and sustainable chemical production. Herein, a seawater piezocatalytic nitrate reduction reaction (NitRR) is demonstrated for efficient NH4+ production by employing MnPS3 nanosheets (NSs) as a new type of piezocatalyst. It is shown that the Mn and P dual sites promote the adsorption and activation of NO3− ions via an asymmetric side-on mode. Moreover, the lattice strain of MnPS3 NSs induced by the external mechanical vibration further weakens the N-O bond. With the additional contribution of the active hydrogen supplied by the S sites, the MnPS3 NSs exhibit an NH4+ production rate of 2.75 mmol h−1 g−1 in simulated seawater without sacrificial agents. By utilizing mechanical energy of water flow in real seawater, continuous conversion of NO3− to NH4+ at a rate of 95.0% and selectivity of 96.4% is also achieved within 120 min. Our work paves the way for sustainable conversion of nitrate in seawater to value-added chemicals via renewable natural energy.