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Emerging wearable devices with noninvasive biosensing technologies have sparked substantial interest for constant monitoring of substances in bodily fluids, which might be used to detect human health issues. Uric acid (UA) is a crucial indicator of a high relationship with gout, hyperuricemia, and Lesch–Nyhan syndrome. Therefore, developing a wearable device to noninvasively monitor the UA levels in sweat has drawn enormous attention. In this work, boron-doped graphene quantum dots anchored to carbon nanotubes (BGQDs/CNTs) were proposed as noble-metal-free electrocatalysts for the design of the enzyme-free wearable sensors to monitor the concentration of UA in human sweat. BGQDs could provide extra active sites to enhance the electrocatalytic ability of the UA oxidation reaction. From the results, BGQDs/CNTs exhibit ultrahigh sensitivity of 8.92 ± 0.22 μA μM–1 cm–2 for UA detection compared to pristine CNTs (4.24 ± 0.24 μA μM–1 cm–2). Moreover, density functional theory calculations indicate that B atoms can strengthen the UA molecule adsorption and enlarge electron transfer from the UA molecule to the B-doped graphene sheet, supporting the high sensitivity of BGQDs for UA detection. Hence, this study offers a promising electrocatalyst for using an enzyme-free electrochemical UA sensor with a dependable and steady performance to further the use of wearable electronics.

Recently, urea electrolysis has been regarded as an up-and-coming pathway for the sustainability of hydrogen fuel production according to its far lower theoretical and thermodynamic electrolytic cell potential (0.37 V) compared to water electrolysis (1.23 V) and rectification of urea-rich wastewater pollution. The new era of the “hydrogen energy economy” involving urea electrolysis can efficiently promote the development of a low-carbon future. In recent decades, numerous inexpensive and fruitful nickel-based materials (metallic Ni, Ni-alloys, oxides/hydroxides, chalcogenides, nitrides and phosphides) have been explored as potential energy saving monofunctional and bifunctional electrocatalysts for urea electrolysis in alkaline solution. In this review, we start with a discussion about the basics and fundamentals of urea electrolysis, including the urea oxidation reaction (UOR) and the hydrogen evolution reaction (HER), and then discuss the strategies for designing electrocatalysts for the UOR, HER and both reactions (bifunctional). Next, the catalytic performance, mechanisms and factors including morphology, composition and electrode/electrolyte kinetics for the ameliorated and diminished activity of the various aforementioned nickel-based electrocatalysts for urea electrolysis, including monofunctional (UOR or HER) and bifunctional (UOR and HER) types, are summarized. Lastly, the features of persisting challenges, future prospects and expectations of unravelling the bifunctional electrocatalysts for urea-based energy conversion technologies, including urea electrolysis, urea fuel cells and photoelectrochemical urea splitting, are illuminated.