Greenly Synthesized Conducting Polymer Nanotunnels with Metal-Hydroxide Nanobundles in Single Dais for Unmitigated Water Oxidation

Abstract

Electrochemical water splitting required efficient electrocatalysts to produce clean hydrogen fuel. Here, we adopted greenway coprecipitation (GC) method to synthesize conducting polymer (CP) nanotunnel network affixed with luminal−abluminal CoNi hydroxides (GC-CoNiCP), namely, GC-Co 1 Ni 2 CP, GC-Co 1.5 Ni 1.5 CP, and GC-Co 2 Ni 1 CP. The active catalyst, GC-Co 2 Ni 1 CP/GC, has low oxygen evolution reaction (OER) overpotential (307 mV) and a smaller Tafel slope (47 mV dec −1 ) than IrO 2 (125 mV dec −1 ). The electrochemical active surface area (EASA) normalized linear sweep voltammetry (LSV) curve exhibited outstanding intrinsic activity of GC-Co 2 Ni 1 CP, which required 285 mV to attain 10 mA cm −2 . At 1.54 V, the estimated turnover frequency (TOF) of GC-Co 2 Ni 1 CP/GC (0.017337 s −1 ) was found to be 3-fold higher than that of IrO 2 (0.0014 s −1 ). Furthermore, the GC-Co 2 Ni 1 CP/NF consumed a very low overpotential (281 mV) with a small Tafel slope of 121 mV dec −1 . The ultrastability of GC-Co 2 Ni 1 CP for industrial application was confirmed by durability at 10 and 100 mA cm −2 for the OER (GC/NF-8 h, 2.0%/100 h, 2.2%) and overall water splitting (100 h, 3.8%), which implies that GC-Co 2 Ni 1 CP had adequate kinetics to address the elevated rates of water oxidation. The effect of pH and addition of tetramethylammonium cation (TMA + ) reveal that GC-Co 2 Ni 1 CP follows the lattice oxygen mechanism (LOM). The solar-powered water electrolysis at 1.55 V supports the efficacy of GC-Co 2 Ni 1 CP in the solar-to-hydrogen conversion. The environmental impact studies and solar-driven water electrolysis proved that GC-CoNiCP has excellent greenness and efficiency, respectively.