Herein, we assessed the capabilities of NiO and Ni(OH)(2) electrodes for L-lactic acid sensing and compared the performances of the corresponding non-enzymatic sensors. Specifically, NiO and Ni(OH)(2) sensors showed high sensitivities, 9.08 and 35.76 mu A/(mM cm(2)) and low detection of limit, 0.53 and 0.59 mM, respectively. Both sensors also show good selectivity and being insensitive to interferents such as I. ascorbic acid, uric acid, and dopamine. Furthermore, electrochemical characterization at variable scan rates revealed that NiO achieves faster sensing than Ni(OH)(2), implying that the above electrodes exhibited different sensing mechanisms. Thus, X-ray photoelectron spectroscopy analysis confirmed that the NiO electrode inherently contained Ni3+ ions acting as active sites for lactate detection and therefore increasing the response speed, whereas Ni(OH)(2) contained no Ni3+ and had to be electrochemically converted into NiOOH prior to analyte detection. Consequently, the NO electrode provided faster and more reliable lactate sensing, thus exhibiting promising non-enzymatic lactate sensor. (C) 2018 Elsevier Ltd. All rights reserved.