We report the development of MOF-derived nitrogen-doped carbon/ Co 3 O 4 nanocomposites (Co 3 O 4 @NCs) with core−shell structures as an efficient electrocatalyst for the artificial nitrogen fixation at room temperature and atmospheric pressure in 0.05 M H 2 SO 4 . It exhibits a high NH 3 yield of 42.58 μg h −1 mg cat.−1 and a faradaic efficiency of 8.5% at −0.2 V versus reversible hydrogen electrode. Experimental results show that the great N 2 reduction reaction performance of Co 3 O 4 @NCs originates from the synergistic effects of N-doped carbon and Co 3 O 4 with significant oxygen vacancy. In addition, we speculate that the core−shell structure can further enhance the electrochemical activity for producing NH 3 .

Bovine mastitis is a common disease occurring in dairy farms and can be caused by more than 150 species of pathogenic bacteria. One of the most common causative organisms is Streptococcus agalactiae, which is also potentially harmful to humans and aquatic animals. At present, research on S. agalactiae in China is mostly concentrated in the northern region, with limited research in the southeastern and southwestern regions. In this study, a total of 313 clinical mastitis samples from large-scale dairy farms in five regions of Sichuan were collected for isolation of S. agalactiae. The epidemiological distribution of S. agalactiae was inferred by serotyping isolates with multiplex polymerase chain reaction. Susceptibility testing and drug resistance genes were detected to guide the clinical use of antibiotics. Virulence genes were also detected to deduce the pathogenicity of S. agalactiae in Sichuan Province. One hundred and five strains of S. agalactiae (33.6%) were isolated according to phenotypic features, biochemical characteristics, and 16S rRNA sequencing. Serotype multiplex polymerase chain reaction analysis showed that all isolates were of type Ia. The isolates were up to 100% sensitive to aminoglycosides (kanamycin, gentamicin, neomycin, and tobramycin), and the resistance rate to β-lactams (penicillin, amoxicillin, ceftazidime, and piperacillin) was up to 98.1%. The TEM gene (β-lactam-resistant) was detected in all isolates, which was in accordance with a drug-resistant phenotype. Analysis of virulence genes showed that all isolates harbored the cfb, cylE, fbsA, fbsB, hylB, and α-enolase genes and none harbored bac or lmb. These data could aid in the prevention and control of mastitis and improve our understanding of epidemiological trends in dairy cows infected with S. agalactiae in Sichuan Province.