Metallic Ni3S2Films Grown by Atomic Layer Deposition as an Efficient and Stable Electrocatalyst for Overall Water Splitting

We describe the direct preparation of crystalline Ni3S2thin films via atomic layer deposition (ALD) techniques at temperatures as low as 250 °C without postthermal treatments. A new ALD chemistry is proposed using bis(1-dimethylamino-2-methyl-2-butoxy) nickel(II) [Ni(dmamb)2] and H2S as precursors. Homogeneous and conformal depositions of Ni3S2films were achieved on 4 in. wafers (both metal and oxide substrates, including Au and SiO2). The resulting crystalline Ni3S2layers exhibited highly efficient and stable performance as electrocatalysts for both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) in alkaline solutions, with a low overpotential of 300 mV and a high turnover frequency for HER and an overpotential of 400 mV for OER (at a current density of 10 mA/cm2). Using our Ni3S2films as both the cathode and the anode, two-electrode full-cell electrolyzers were constructed, which showed stable operation for 100 h at a current density of 10 mA/cm2. The proposed ALD electrocatalysts on planar surfaces exhibited the best performance among Ni3S2materials for overall water splitting recorded to date.