Synergistic Incorporating RuO 2 and NiFeOOH Layers onto Ni 3 S 2 Nanoflakes with Modulated Electron Structure for Efficient Water Splitting.

Synergistic electronic modulations is an effective strategy to develop efficient and stable electrocatalysts for the electrochemical hydrogen production via water splitting. Herein, tremella-like Ni 3 S 2 @RuO 2 and Ni 3 S 2 @NiFeOOH heterostructures catalysts are constructed on Ni foams (NF) by coupling RuO 2 and NiFeOOH on Ni 3 S 2 nanoflake arrays. The resulting Ni 3 S 2 @RuO 2 /NF electrode exhibits top-level hydrogen evolution reaction electrocatalysis with an extremely low overpotential of 12 mV at 10 mA cm -2 and a Tafel slope of 30.7 mV dec -1 , as well as the as-obtained Ni 3 S 2 @NiFeOOH/NF electrode with tunable binding energy for OH* intermediates shows remarkable oxygen evolution reaction electrocatalysis with an overpotential of 227 mV at 10 mA cm -2 . The electrolyzer employing Ni 3 S 2 @RuO 2 /NF electrode for cathodic H 2 production and Ni 3 S 2 @NiFeOOH/NF for anodic O 2 production merely needs a low voltage of 1.47 V to drive 10 mA cm -2 with excellent durability. The combined theoretical calculation and X-ray photoelectron spectroscopy investigation reveal that heterogeneous configuration can induce electron transfer from Ni 3 S 2 to RuO 2 through NiRu/SRu bonds, and thus tailor the d-band center and optimize the activated H 2 O/H* Gibbs free energies for enhanced hydrogen evolution reaction on Ni 3 S 2 @RuO 2 . This study may shed new light on the construction of heterostructures as highest-performing electrocatalysts and offer unique insight into the theory mechanism.