Bio-inspired Nickel-Iron Based Organogel: An Efficient and Stable Bifunctional Electrocatalyst for Overall water splitting in high current density

Abstract

ABSTRACT. Developing platinum group metal (PGM) free electrocatalyst remains prime challenges for cost effective green hydrogen (H2) production. Herein, mimicking the PSII catalyst, a bimetallic organo gel of Nickel (Ni2+), iron (Fe3+) and benzotriazole (NiFe-gel) is developed as efficient electrocatalyst. The developed synthetic strategy is simple and scalable and most importantly, no binder is required for gel loaded electrode preparation. The respective gel based electrode showed excellent bifunctional, both OER and HER, water electrolysis activity in low as well as high current density (η10: 110 mV and η1000: 260 mV for OER, and η10: 88 mV and η1000: 324 mV for HER), low Tafel slope and outstanding stability for 100 h current density of 1A cm ̶ 2. The two electrode electrolyser using the developed NiFe-gel in both anode and cathode for overall water splitting attain current density of 10 mA cm-2 and 1A cm-2 at a potential of 1.49 V and 1.89 V, respectively. Most significantly, NiFe-gel loaded anion exchange membrane based 4 cm2 alkaline water electrolysis (AEMAWE) attain current density of 1.08 A cm-2 at 50 ⁰C and 2V, and showed stability for at least 100 h. Very nominal performance reduction was observed on scale-up of electrolyser from 4 cm2 to 9 cm2 and the performance is better than the targeted AEMAWE performance of ≥1A cm-2 at 2V. The excellent performance is attributed to the synergistic electronic interaction between Fe3+ and Ni2+, interaction of nitrogen rich triazole moieties attached with metal site, similar to the PS II system, and porous electrode microstructure. Thus NiFe-gel might be alternative as a potential PGM free electrocatalyst for industrial scale hydrogen production through water electrolysis.