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Owing to their high catalytic activity, transition metal hydroxides are promising electrocatalysts for non-enzymatic glucose sensors. The hydroxyl functionalities in Co1–xNix hydroxide/mixed anionic hydroxides play a vital role in their electrochemical activation via conversion to an oxyhydroxide catalyst and thus impact their sensitivity to small molecule (glucose) oxidation. Herein, we report the rational synthesis of M2(OH)4–n(An–) compositions (0 > n ≤ 2) with hydroxide (OH)-rich and OH-deficient phases, viz., CoNi-hydroxide nitrate (CoNi-HN) and CoNi-hydroxide carbonate (CoNi-HC), by using different solvents of ethanol and water, under solvo/hydrothermal conditions, respectively. The OH-rich CoNi-HN phase exhibited enhanced pre-activation efficiency, which accelerated the glucose oxidation kinetics, and beneficial morphological features (flower-like structures with interconnected nanosheets). The OH-rich CoNi-HN catalyst, which is the first report for a glucose sensor, exhibited superior sensing property with a high sensitivity of ∼136 μA mM–1 cm–2. The structure–(sensing) property relationship was analyzed in detail by tailoring the morphology to form an OH-rich graphene oxide (GO) hybrid. The CoNi-HN/GO hybrid exhibited improved glucose oxidation, delivering a wide glucose-sensing range, with a sensitivity of ∼268 μA mM–1 cm–2, a low detection limit of 28.5 μM (S/N = 3), and good selectivity. The excellent sensitivity of this hybrid was attributed to the synergism between the OH-rich CoNi-HN phase and the OH-rich interfaces between GO and CoNi-HN, as well as a unique flower-like morphology with interconnected nanosheets. Insights into the critical role of hydroxyl groups in the electrocatalytic performance of transition-metal-based catalysts have been emphasized in this work.
Gayathri et al. (Thu,) studied this question.