Controlled Synthesis of Cr-Co0.85 Se Nanoarrays for Water Splitting at an Ultralow Cell Voltage of 1.43 V.

Water splitting has attracted more and more attention as a promising strategy for the production of clean hydrogen fuel. In this work, a new synthesis strategy was proposed, and Co0.85 Se was synthesized on nickel foam as the main matrix. The doping of appropriate Cr amount into the target of Co0.85 Se and the Cr-Co0.85 Se resulted in an excellent electrochemical performance. The doping of Cr introduces Cr3+ ions which substitute Co2+ and Co3+ ions in Co0.85 Se, so that the lattice parameters of the main matrix were changed. It is worth noting that the Cr0.15-Co0.85 Se/NF material exhibits an excellent performance in the oxygen evolution reaction (OER) test. When the current density reaches 50 mA cm-2 for OER, the overpotential is only 240 mV. For the hydrogen evolution reaction (HER) tests, the overpotential is only 117 mV to drive 10 mA cm-2 of current density. Moreover, when the Cr0.15-Co0.85 Se/NF material is used as a two-electrode device for whole water splitting, the required cell voltage is only 1.43 V to reach a current density of 10 mA cm-2 , which is among the lowest values of the published catalysts up to now. In addition, the Cr0.15-Co0.85 Se/NF catalyst also exhibits excellent stability during a long period of water splitting. The experimental result demonstrates that the change of the lattice structure has an obvious influence on the electrocatalytic activity of the material. When an external electric field is applied, it facilitates the rapid electron transfer rate and enhances the electrocatalytic performance and stability of the material.