In-situ growing low-crystalline Co9S8-Ni3S2 nanohybrid on carbon cloth as a highly active and ultrastable electrode for the oxygen evolution reaction

ABSTRACT The highly active electrodes for the oxygen evolution reaction (OER) are vital for boosting the overall efficiency of electrocatalytic water splitting to produce hydrogen fuel. Here we demonstrate a facile in-situ sulfurization strategy to construct an additive-free electrode with low-crystalline Co9S8-Ni3S2 nanohybrid under the joint effects of fast sulfurization and lattice-mismatched growth. The Co9S8-Ni3S2 nanohybrid exhibits semi-spherical architecture constructed with interconnected nanoflakes, and contains mesopores with an average pore size of 12.66 nm. The crystalline degrees of Ni3S2 and Co9S8 in the nanohybrid are estimated to be as low as 18.66% and 5.46%, respectively. For OER in 1 M KOH, the electrode attains a benchmark of 10 mA cm−2 at a very low overpotential (η10) of 220 mV and impressively demonstrates the outstanding OER stability lasting for 900 h at about 50 mA cm−2, which highlights its great potential applications in water splitting devices. More importantly, this work discloses the crucial contribution from low-crystalline Co9S8-Ni3S2 nanohybrid to the high-efficiency OER, the key role of dynamic balance related to electroctatalytic activity in sustaining the ultralong-term stability, and the mechanisms behind the matter evolutions from Co9S8-Ni3S2 into CoOOH-NiOOH species.