Enhancing catalytic performance of Fe and Mo co-doped dual single-atom catalysts with dual-enzyme activities for sensitive detection of hydrogen peroxide and uric acid

Single-atom catalysts (SACs) have attracted much attention due to their excellent catalytic activity, but the improvement of atomic loading which means that weight fraction (wt%) of metal atom was still facing great challenges. In this work, iron and molybdenum co-doped dual single-atom catalysts (Fe/Mo DSACs) was prepared for the first time by using the soft template sacrifice strategy, which improved significantly the atomic load and exhibited both the oxidase-like (OXD) activity and the dominant peroxidase-like (POD) activity. Further experiments reveal that Fe/Mo DSACs can not only catalyze O2 to generate O2•- and 1O2, but also catalyze H2O2 to generate a large number of •OH, which caused 3, 3', 5, 5'-tetramethylbenzidine (TMB) to be oxidized to oxTMB, accompanied by the color changing from colorless to blue. The steady-state kinetic test showed that Michaelis-Menten constant (Km) values and the maximum initial velocity values (Vmax) of the POD activity of Fe/Mo DSACs were 0.0018 mM and 12.6 × 10-8 M s-1, respectively. The corresponding catalytic efficiency was tens of times higher than Fe SACs and Mo SACs, which proves that the synergistic effect between Fe and Mo has significantly improved the catalytic ability. Based on the excellent POD activity of Fe/Mo DSACs, a colorimetric sensing platform combined with TMB was proposed to realize the sensitive detection of H2O2 and uric acid (UA) in a wide range, with limits of detection as low as 0.13 and 0.18 μM, respectively. Finally, accurate and reliable results were obtained in the detection of H2O2 in cells, and of UA in human serum and urine.