Preparation Of Co₃o₄/Red Phosphorus Composite Photocatalyst And Its Visible-light Photocatalytic Performance

Photocatalytic technology can directly use solar energy to decompose organic pollutants,and can also convert solar energy into hydrogen energy.The photocatalytic activities of traditional TiO₂ and ZnO photocatalysts are limited to the ultraviolet region.Therefore,there is a need to develop stable and efficient visible-light-driven photocatalyst.Red phosphorus semiconductor has photocatalytic activity under visible light illumination.However,the photo-induced electrons and holes of red phosphorus semiconductors are easy to recombine,thereby limiting the photocatalytic performance.In order to improve the red phosphorus semiconductor photocatalytic performance,in this paper,the Co₃O₄/red phosphorus?Co₃O₄/RP?composite material was prepared,and the surface was modified by the co-catalyst.The catalyst was analyzed by a series of characterizations,and the photocatalytic performance of the catalyst in the reaction was evaluated by degradation of malachite green?MG?and photocatalytic hydrogen production.Firstly,Co₃O₄/RP composite photocatalyst was prepared by facile hydrothermal and mechanically grinding method.A series of characterizations showed that Co₃O₄nanocrystals were assembled on the surface of the RP.Compared with pure RP,the loading of Co₃O₄ on RP was beneficial to enhance the light absorption in the visible light range.The Co₃O₄/RP demonstrated notably high photocatalytic activity over a wide range of composition than the bare Co₃O₄ and RP for the degradation of MG in aqueous phase under visible light irradiation.The reaction rate constant of 10%Co₃O₄/RP heterojunction(0.1464 min^-1)is about 3.2 times as high as that of pure RP(0.0457 min^-1),and 15.3 times than that of the bare Co₃O₄(0.0096 min^-1).The experimental results of adding different sacrificial agents showed that·O₂^-and h⁺played a major role in the photocatalytic degradation of MG.The cycle experiments showed that the catalyst had a high photocatalytic stability.Co₃O₄ nanocrystals inhibit the photoelectron-hole pairs recombination of red phosphorus semiconductor,and the visible light absorbance has been improved.Consequently,the RP photocatalytic performance has been enhanced.Secondly,the property of photocatalytic water splitting hydrogen production with Co₃O₄/RP photocatalyst was studied under visible light irradiation.The experimental results showed that the H₂ production rate of 10%Co₃O₄/RP composite material reached 65.1 mol·g^-1·h^-1,which was 59.2 times of the unmodified RP(1.1mol·g^-1·h^-1).The composite catalysts of Co-10%Co₃O₄/RP and Pt-10%Co₃O₄/RP were synthesized by simple photoreduction method.A series of characterizations showed that Co element deposition on the surface of 10%Co₃O₄/RP,compared with10%Co₃O₄/RP,the 0.5%Co-10%Co₃O₄/RP improved the hydrogen production performance in photocatalytic water splitting.The cycle experiments show that the catalyst has high photocatalytic stability.Compared with noble metal Pt,the hydrogen production rate of 0.5%Co-10%Co₃O₄/RP(82.7 mol·g^-1·h^-1)was 1.2 times of0.5%Pt-10%Co₃O₄/RP(67.6 mol·g^-1·h^-1),which means that low-cost transition metal Co is expected to replace high-cost noble metal Pt and becomes an excellent catalyst.