Confined synthesis of well-dispersed NiCo2S4 nanowires on nitrogen-doped reduced graphene oxide aerogel for efficient electrocatalytic overall water splitting

The development of facile and cost-efficient synthetic strategies to prepare highly active catalysts is essential for water electrolysis. Here, a confined synthetic strategy is developed to fabricate NiCo2S4 with controllable morphology (nanowires vs nanosheets) anchored on nitrogen-doped reduced graphene oxide (N-rGO) aerogels. Specifically, well-dispersed NiCo2S4 nanowires are finely wrapped in the high conductive N-rGO (NiCo2S4 NWs/N-rGO) to provide abundant active sites and accelerate the electron/ion diffusion between the electrode and electrolyte. Consequently, the NiCo2S4 NWs/N-rGO aerogel electrode exhibits much enhanced electrocat-alytic activity for both HER and OER with low overpotentials of 96 and 230 mV at a current density of 10 mA cm-2, respectively. Moreover, an alkaline electrolyzer assembled by two NiCo2S4 NWs/N-rGO elec-trodes exhibits superior performance for overall water splitting with a small cell voltage of 1.556 V at 10 mA cm-2. This work demonstrates a simple and manageable route to construct conductive carbon-support transition metal-based nanocomposites for electrocatalysis.