Hydrothermal nickel selenides as efficient electrodes in alkaline media: application to supercapacitors and the...

The advancement of active electrochemical materials is pivotal for enhancing energy conversion and storage technologies, which is essential for a sustainable future. Furthermore, achieving cost-effective technologies necessitates avoiding the use of noble metals and low-throughput processes that require high vacuum or high temperatures. Herein, we describe in detail a simple solution-based protocol to obtain a series of phase-controlled nickel selenide nanomaterials. The electrochemical performance of these materials, influenced by the phase and morphology, has been further analyzed. To showcase the application of these materials, two technologies are considered: (i) supercapacitors; and (ii) the methanol oxidation reaction (MOR). In particular, the Ni₃Se₄-based electrode in 1 M KOH shows an initial specific capacitance of 1903.5 F g^-1 at a discharge current of 0.1 mA and displays a notable stability for over 3000 cycles. Furthermore, in an alkaline medium with methanol, this electrode produces a current density of 95.5 mA cm^-2, facilitating methanol-to-formate conversion with a faradaic efficiency of up to 95.7% during a continuous 20-hour test. This research underscores the potential of nickel selenide nanomaterials in driving the next generation of energy storage and conversion technologies.