Sonication-Induced Boladipeptide-Based Metallogel as an Efficient Electrocatalyst for the Oxygen Evolution Reaction

Bioinspired, self-assembled hybrid materials show great potential in the field of energy conversion. Here, we have prepared a sonication-induced boladipeptide (HO-YF-AA-FY-OH (PBFY); AA = Adipic acid, F = l-phenylalanine, and Y = l-tyrosine) and an anchored, self-assembled nickel-based coordinated polymeric nanohybrid hydrogel (Ni-PBFY). The morphological studies of hydrogels PBFY and Ni-PBFY exhibit nanofibrillar network structures. XPS analysis has been used to study the self-assembled coordinated polymeric hydrogel Ni-PBFY-3, with the aim of identifying its chemical makeup and electronic state. XANES and EXAFS analyses have been used to examine the local electronic structure and coordination environment of Ni-PBFY-3. The xerogel of Ni-PBFY was used to fabricate the electrodes and is utilized in the OER (oxygen evolution reaction). The native hydrogel (PBFY) contains a gelator boladipeptide of 15.33 mg (20 mmol L^-1) in a final volume of 1 mL. The metallo-hydrogel (Ni-PBFY-3) is prepared by combining 15.33 mg (20 mmol L^-1) of boladipeptide (PBFY) with 3 mg (13 mmol L^-1) of NiCl₂·6H₂O metal in a final volume of 1 mL. It displays an ultralow Tafel slope of 74 mV dec^-1 and a lower overpotential of 164 mV at a 10 mA cm^-2 current density in a 1 M KOH electrolyte, compared to other electrocatalysts under the same experimental conditions. Furthermore, the Ni-PBFY-3 electrocatalyst has been witnessed to be highly stable during 100 h of chronopotentiometry performance. To explore the OER mechanism in an alkaline medium, a theoretical calculation was carried out by employing the first-principles-based density functional theory (DFT) method. The computed results obtained by the DFT method further confirm that the Ni-PBFY-3 electrocatalyst has a high intrinsic activity toward the OER, and the value of overpotential obtained from the present experiment agrees well with the computed value of the overpotential. The biomolecule-assisted electrocatalytic results provide a new approach for designing efficient electrocatalysts, which could have significant implications in the field of green energy conversion.