Doping phosphorus into Co3O4: A new promising pathway to boost the catalytic activity for peroxymonosulfate activation

Abstract

Recently, Co3O4 has been widely utilized as heterogeneous catalyst for peroxymonosulfate (PMS) activation to eliminate various organic pollutants. However, for practical applications, the catalytic efficiency of pure Co3O4, limited by its simple monometal oxide component, needs further improvement. In a departure from the conventional doping method employing metal elements as dopants, herein, it is demonstrated that non-metal element doping offers a new and promising avenue to optimize the property of Co3O4 and thus improve its catalytic performance. This was exemplified by phosphorus (P)-doped Co3O4 (P-Co3O4), which was obtained by a simple low-temperature annealing of commercial Co3O4 using NaH2PO2 as the P source. Noticeably, owing to the presence of P dopants (0.15 wt%), the cobalt sites in P-Co3O4 exhibited higher affinity, easier electron transfer, and stronger bond-weakening ability for PMS relative to those in non-doped Co3O4, which led to a boosted catalytic activity. The degradation of rhodamine B (RhB) by P-Co3O4/PMS was verified to be SO4−- and 1O2-dominated and underwent a multistep mineralization pathway, and its kinetic rate constant (0.139 min−1) was 4.5 times that (0.031 min−1) of RhB degradation by Co3O4/PMS. Moreover, the P-Co3O4 exhibited excellent reusability, without obvious catalytic activity loss after six successive runs. Our work presents an unconventional strategy for designing cost-effective and efficient heterogeneous cobalt-based catalysts for PMS activation.