Sihua Wu,Jinhui Zou,Baohua Zhang,Jiantian Lu,Guan Rong Lin,Yuwei Zhang,Li Niu
Nickel oxide (NiO) nanozyme, as an excellent oxidase mimic, have been widely used in fluorescence biological detection, water pollutant analysis, food safety and cell imaging. However, to fully achieve these applications, it is still a great challenge to regulate its crystalline micro/nanostructure and composites to achieve high enzyme activity and high specific surface area. Here, we applied a very simple thermal annealing treatment to restructure the calcined precursor of NiO. Importantly, it was found that oxygen vacancy (OV) concentration of the targeted NiO nanozyme is significantly increased while the annealing atmosphere is argon rather than air. Moreover, the as-prepared novel NiO sample (NiO-OV) nanosheets achieved ca. 2-fold enhancement in specific surface area. It is believed that the higher OV concentration and the larger specific surface area will increase the enzyme activity by accelerating electron transfer rate and increasing catalytic interfaces. The significant improvement of enzyme activity of NiO-OV was verified by the fluorescence "turn-on" experiment of Amplex red (AR). Finally, using NiO-OV/AR system, we constructed a highly sensitive enzyme sensor on L-Cys with a detection limit of 37.8 nM. It also displayed an excellent specificity for ten typical amino acid interferences.
Qimin Peng,Xiaoling Zhuang,Longgui Wei,Luyan Shi,Tayirjan Taylor Isimjan,Ruobing Hou,Xiulin Yang
Graphical A thorny challenge : A nanothorn-like superhydrophilic Nb−CoSe 2 /CC (CC=carbon cloth) catalyst is fabricated through a facile in-situ hydrothermal selenization and Ar annealing strategies. The catalyst illustrates an excellent oxygen evolution activity (297 mV at 200 mA cm −2 ), outstanding long-term durability, and good overall water splitting performance (1.93 V at 500 mA cm −2 ). Developing cost-effective, highly active, and robust electrocatalysts for oxygen evolution reaction (OER) at high current density is a critical challenge in water electrolysis since the sluggish kinetics of the OER significantly impedes the energy conversion efficiency of overall water splitting. Here, a 1D nanothorn-like Nb−CoSe 2 /CC (CC=carbon cloth) structure was developed as an efficient OER catalyst. The optimized Nb−CoSe 2 /CC catalyst exhibited remarkable OER performance with the low overpotentials of 220 mV at 10 mA cm −2 and 297 mV 200 mA cm −2 and a small Tafel slope (54.1 mV dec −1 ) in 1.0 m KOH electrolyte. More importantly, the Nb−CoSe 2 /CC electrode displayed superior stability after 60 h of continuous operation. In addition, cell voltages of 1.52 and 1.93 V were required to achieve 10 and 500 mA cm −2 for the electrolyzer made of Nb−CoSe 2 /CC (anode) and the Pt/C (cathode). Density functional theory (DFT) calculations combined with experimental results revealed that incorporating niobium into the CoSe 2 could optimize the adsorption free energy of the reaction intermediates and enhance the conductivity to improve the catalytic activity further. Additionally, the super-hydrophilicity of Nb−CoSe 2 /CC resulting from the surface defects increased the surface wettability and facilitated reaction kinetics. These results indicate that Nb−CoSe 2 /CC intrinsically enhances OER performance and possesses potential practical water electrolysis applications.
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