Coordination environment engineering of MoS2-based nanocomposite by Ni atom incorporation for enhanced peroxymonosulfate activation

Ni-doped MoS2 can activate PMS effectively to degrade organic pollutants because the Ni doping can modulate the adsorption energy barrier of MoS2 to PMS molecule. However, how the coordination environment between Ni and MoS2 affects the activation of PMS to generate active species is poorly understood. In this paper, Ni substitutional or Ni adsorptive doping of MoS2 supported on TiO2/N-doped carbon nanofibers (designated as Nisub-MTC or Niads-MTC, respectively) were synthesized and used as PMS activators to degrade tetracycline (TC), respectively. In the case of Niads-MTC that the Ni atoms adsorb atop of S vacancies in MoS2, the reaction kinetic constant for TC degradation can reach 0.3381 min−1 within 10 min in Niads-MTC/PMS/Vis system. That is 1.84 times higher than that in Nisub-MTC/PMS/Vis system (0.1835 min−1), where the Mo sites in MoS2 are substituted with Ni atoms. This possibly due to that the Ni adsorptive doping can improve the regional activity of Mo-S bonds, which is more efficient than increasing the S vacancies by Ni substitutional doping. DFT calculations further support that the lower adsorption energy barriers of PMS were obtained on Ni adsorptive doping MoS2. Moreover, the main active species and possible TC degradation pathways were proposed. This work provides a new insight for designing metal doped heterogeneous catalysts with suitable coordination environments to improve PMS activation efficiency.