Efficient and Stable Degradation of <i>p</i> -Nitrophenol over Zinc-Doped Cobalt Oxide for Wastewater Treatment

The selective catalytic reduction of p-nitrophenol (PNP) to p-aminophenol (PAP) not only mitigates the toxicity of industrial wastewater but also enables resource recovery, representing a promising strategy for sustainable pollutant treatment and wastewater purification. In this study, a zinc-doped cobalt oxide catalyst synthesized via a one-step hydrothermal method was applied to the selective reduction of PNP to PAP. The catalyst demonstrated complete PNP degradation (100%), full selectivity toward PAP (100%), and excellent stability. Isotope tracing experiments were conducted to address the debated issue about the source of activated atomic hydrogen (H*) in the selective reduction of PNP. The results revealed that water acts as the primary source of H* for the catalytic reduction, while sodium borohydride functions as an electron donor. Furthermore, the zinc-doped cobalt oxide catalyst was still robust for PNP degradation in real water samples. This work offers an active and stable catalyst for the selective catalytic reduction of other nitroaromatic pollutants in waste effluents.