Greenly Synthesized\nConducting Polymer Nanotunnels\nwith Metal-Hydroxide Nanobundles in Single Dais for Unmitigated Water\nOxidation

Electrochemical water splitting required efficient electrocatalysts\nto produce clean hydrogen fuel. Here, we adopted greenway coprecipitation\n(GC) method to synthesize conducting polymer (CP) nanotunnel network\naffixed with luminal–abluminal CoNi hydroxides (GC-CoNiCP),\nnamely, GC-Co<sub>1</sub>Ni<sub>2</sub>CP, GC-Co<sub>1.5</sub>Ni<sub>1.5</sub>CP, and GC-Co<sub>2</sub>Ni<sub>1</sub>CP. The active catalyst,\nGC-Co<sub>2</sub>Ni<sub>1</sub>CP/GC, has low oxygen evolution reaction\n(OER) overpotential (307 mV) and a smaller Tafel slope (47 mV dec<sup>–1</sup>) than IrO<sub>2</sub> (125 mV dec<sup>–1</sup>). The electrochemical active surface area (EASA) normalized linear\nsweep voltammetry (LSV) curve exhibited outstanding intrinsic activity\nof GC-Co<sub>2</sub>Ni<sub>1</sub>CP, which required 285 mV to attain\n10 mA cm<sup>–2</sup>. At 1.54 V, the estimated turnover frequency\n(TOF) of GC-Co<sub>2</sub>Ni<sub>1</sub>CP/GC (0.017337 s<sup>–1</sup>) was found to be 3-fold higher than that of IrO<sub>2</sub> (0.0014\ns<sup>–1</sup>). Furthermore, the GC-Co<sub>2</sub>Ni<sub>1</sub>CP/NF consumed a very low overpotential (281 mV) with a small Tafel\nslope of 121 mV dec<sup>–1</sup>. The ultrastability of GC-Co<sub>2</sub>Ni<sub>1</sub>CP for industrial application was confirmed\nby durability at 10 and 100 mA cm<sup>–2</sup> for the OER\n(GC/NF-8 h, 2.0%/100 h, 2.2%) and overall water splitting (100 h,\n3.8%), which implies that GC-Co<sub>2</sub>Ni<sub>1</sub>CP had adequate\nkinetics to address the elevated rates of water oxidation. The effect\nof pH and addition of tetramethylammonium cation (TMA<sup>+</sup>)\nreveal that GC-Co<sub>2</sub>Ni<sub>1</sub>CP follows the lattice\noxygen mechanism (LOM). The solar-powered water electrolysis at 1.55\nV supports the efficacy of GC-Co<sub>2</sub>Ni<sub>1</sub>CP in the\nsolar-to-hydrogen conversion. The environmental impact studies and\nsolar-driven water electrolysis proved that GC-CoNiCP has excellent\ngreenness and efficiency, respectively.