Piezocatalytic nitrate reduction to ammonia in seawater

The renewable-energy-driven conversion of nitrate in seawater into ammonia ions (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 the mechanical energy of water flow in real seawater, the continuous conversion of NO₃ ^- into NH₄ ⁺ at a rate of 95.0% and with a selectivity of 96.4% is also achieved within 120 min. Our work paves the way for the sustainable conversion of nitrate in seawater into value-added chemicals via renewable natural energy.