Unveiling\nthe Multifunction of SCoFeCS: Remarkably\nBoosting Electrocatalytic Activity in Renewable Energy-Powered Overall\nAlkaline Water Splitting

We developed core–shell structured (CS) CoFe hydroxides\ncoated by a defective RGO shell via solvothermal (SCoFeCS) and hydrothermal\n(HCoFe@RGO) methods. SCoFeCS provided more active sites with a transmissive\ncorridor and high conductivity, with a large surface area, to ameliorate\nthe catalytic efficiency. The optimal SCoFeCS displays exceptional\ntrifunctional properties for H<sub>2</sub> and O<sub>2</sub> evolution,\nUOR, and MSWO at low potentials (OER: 299 mV; 112 mV dec<sup>–1</sup>, UOR: 1.40 V; 72 mVdec<sup>–1</sup>, and MSWO: 1.50 V; 82\nmVdec<sup>–1</sup>). SCoFeCS shows higher catalytic efficiency\nthan HCoFe@RGO (359 mV; 299 mV dec<sup>–1</sup>) due to strong\nsynergistic coupling between CoFe and the rGO matrix. The calculated\nareas under MOOH formation peaks for SCoFeCS, HCoFe@RGO, and SCo@RGO\nare 2.603 × 10<sup>–5</sup> AV, 1.139 × 10<sup>–5</sup> AV, and 1.079 × 10<sup>–5</sup> AV and active sites\nare 3.249 × 10<sup>16</sup>, 1.422 × 10<sup>16</sup>, and\n1.347 × 10<sup>16</sup>, respectively. The superaerophobicity\nof SCoFeCS is validated by the fast gas bubble evolution from the\nSCoFeCS surface. The ultrastability of SCoFeCS for industrial application\nwas confirmed by durability at 10/100 mA cm<sup>–2</sup> for\nOER (GC: 24 h, 2.4%/-; NF: 100 h, 3.2/5.1%), UOR (100 h/2.8%), MMSWO\n(100 h/3.4%), and overall water splitting (100 h, 2.7%/4.1%). The\neffect of pH and the addition of tetramethylammonium cation (TMA<sup>+</sup>) reveal that SCoFeCS follows the lattice oxygen mechanism\n(LOM). The multiapplications of SCoFeCS proposed to be an auspicious\ncatalyst for fuel cell applications.