Exploring the high catalytic performances of Cu–Co–O/N-doped carbon materials toward the hydrogenation reduction and advanced oxidation reactions of 4-nitrophenol (PNP)

Abstract

This work reports the high catalytic performances of Cu–Co–O/N-doped carbon materials toward the hydrogenation reduction and advanced oxidation reactions of 4-nitrophenol (PNP). By incorporating Cu²⁺ and Co²⁺ with atomic ratios from 1 : 9 to 1 : 4, 1 : 2, 1 : 1, 9 : 1, and 19 : 1, catalysts prepared at 500 °C in air via sol–gel method demonstrated superior catalytic ability toward the two reactions than those prepared at 600 °C. The crystalline phase of the catalyst with an atomic ratio of 1 : 1 was determined to be CuO and Cu_0.92Co_2.08O₄, and a reaction time of 4.5 min and activity parameter of 300 s⁻¹ g⁻¹ could be obtained for the reduction reaction of PNP over this CuO–Cu_0.92Co_2.08O₄/N-doped carbon material when the NaBH₄ : PNP molar ratio was 100 : 1. The activity parameters were 300 s⁻¹ g⁻¹ and 294 s⁻¹ g⁻¹ for catalysts with Cu²⁺ : Co²⁺ atomic ratios of 1 : 9 and 19 : 1, respectively, and the main contribution toward the catalytic performance is discussed in terms of oxygen vacancies or synergistic effects. The CuO–Cu_0.92Co_2.08O₄/N-doped carbon material also had desirable catalytic ability toward the advanced oxidation reaction of PNP using peroxymonosulfate (PMS) as an oxidation agent, whereby an activity parameter of 51.7 s⁻¹ g⁻¹ could be obtained when the PMS : PNP molar ratio was 14 : 1. Our results provide new insights into promoting the catalytic property of transitional oxide-based catalysts.