Preparation Of Stable Cobalt(Nickel) Nitride And Its Catalytic Performance For P-nitrophenol Reduction

The energy and environmental issues associated with economic development are the focus of worldwide attention.Water resources are directly related to human daily life and physical health,so water pollution issues have caused widespread concern.Heavy metal ions,organic matter(hormones,dyes,aromatic compounds,pesticides,etc.)are common contaminants that cause water pollution.Among them,aromatic nitro compounds such as nitrophenol are extremely harmful to humans,animals and plants.The corresponding reduction product,aminophenol,is not only easily biodegradable,but also has a higher added value.Due to the high cost of the conventional precious metal-based catalytic materials,it is necessary to develop a cheap and easy-to-use,easy-to-separate catalyst with good cycle performance.The late transition metal(cobalt,nickel)nitride is a potential catalyst,which has the advantages of being cheap and easy to obtain.This paper is devoted to the study of various methods for preparing structurally stable cobalt(nickel)nitrides.A catalyst system for catalytic reduction of nitrophenol which is highly active and easily separated is obtained by a method of silica coating,self-supporting array construction,and the like.The main contents of the paper are as follows:Firstly,the silica-based coating can effectively solve the problem of easy agglomeration of nitride(Ni3N),thereby facilitating the use and separation of the catalyst.We synthesized silica-coated Ni3N in high yield based on a coordination assembly method.The precursor was obtained by coordination of the silicon source with amino group and metal.The Ni3N@SiO2 catalyst obtained by optimizing the calcination conditions has a good catalytic performance for the reduction of p-nitrophenol,and the catalytic conversion rate reaches 97.8%at 10 min.Selective etching of SiO2 via sodium hydroxide exposes NisN partially,and the catalytic performance is further improved.The conversion rate reaches 99.9%in 4 min.Importantly,the catalyst can be separated using a magnet to facilitate separation and recycling.Secondly,the conventional powder catalyst is generally not easily separated from the reaction medium,and the high temperature is liable to agglomerate,resulting in poor recycling ability,which is disadvantageous for practical use.Even with a magnetic powder catalyst,there is a partial loss of the catalyst after magnetic separation.In response to this problem,we have developed an effective method for immobilizing cobalt-nickel nitride on nickel nitrite(NF)for the preparation of low cost catalysts.The performance was evaluated by the reduction of 4-nitrophenol to 4-aminophenol as a model reaction.After 5 min of reaction at 25?,the conversion can reach 97.6%,which is comparable to most non-precious metal based catalysts.Since the nitride is fixed on the foamed nickel substrate,it can be separated using tweezers,has high stability,and can avoid loss during the separation process.The performance of the catalyst is further improved when it is used at 75?,and the conversion rate is close to 100%within 20 s.Especially after 20 cycles,the activity was well maintained,much better than previously reported catalysts.Finally,based on the low price of biomass cotton,its fibrous structure and its ability to maintain its morphology after calcination,cotton was chosen as a carrier to replace the higher cost foamed nickel.After assembly,the cobalt source is loaded on the cotton and then calcined at a high temperature to obtain a Co4N/C nanomaterial.The catalyst exhibited good performance in catalyzing 4-nitrophenol with a conversion rate of 99.4%at 3 min.Since the spherical form remains after calcination,it can be taken out with tweezers after the reaction,and the reaction is stopped in time.Due to the low cost and natural regeneration of biomass,this method has great practicality.