Metal Organic Framework Derived Electrocatalyst for Water Splitting Application

Abstract

Hydrogen, derived from renewable sources is credited as a clean and energy-abundant fuel, presenting significant promise for fostering a sustainable future. Water is a rich resource among all on the Earth’s surface. It is applicable as a raw source for green Hydrogen production. Green Hydrogen is generated through an “electrochemical water splitting” process that incorporates two mechanisms. These half-cell mechanisms are called “Hydrogen Evolution reaction (HER) and Oxygen Evolution Reaction (OER)”. However renewable processes suffer a slow kinetics. To promote the separation of hydrogen and oxygen molecules through water, electrocatalyst is necessitated. So electrocatalysts are critical in the creation of green H2 production. Commonly, commercial metal catalysts like” Platinum, Iridium, and Ruthenium” are employed for their exceptional performance. Yet, these materials are not suitable for industrial application due to excessive cost and scarcity of resources in nature. These constraints pose challenges for their widespread application in large-scale electrolysis processes. To commercialize the process efficiently, it is necessary to substitute rare metals with base metals, which should be highly conductive as electrocatalysts and can improve their activity, selectivity, and stability. Because of their availability, remarkable catalytic activity, and stability, modified transition metals in a transform of “Metal-Organic Frameworks (MOFs)” have shown promise as a viable alternative to costly metals. These crystalline materials possess porosity and unique structural characteristics, which enable them exceptional candidates for electrochemical water splitting. Notably, the catalyst material's physical structural morphology plays a critical role in shaping its effectiveness in boosting the process. Hence, optimization of the composition and structure of catalysts is vital to enrich the proficiency of the “water splitting” development. In existing research work, three series of catalysts are designed for water splitting application study. The project's main objective is to synthesize stable and active metal electrocatalyst for “water splitting” belonging to the transition metal family. The study focused on synthesizing and modifying the Zeolite Imidazole Framework (ZIF 67) as a working electrode catalytic material for “overall water-splitting applications”. To lift the performance of ZIF-67 catalyst is further modified by conjugating with the carbon xxii support. For instantly reduced graphene oxide (rGO), graphitic carbon nitride (g-C3N4), and, multi-walled carbon nanotubes (MWCNT) are cast-off which also take part in the improvement of the stability of catalyst. These materials offered promising results due to their low overpotential for OER and HER activity. The composite materials are synthesized through solvothermal heat treatment process. Different physical characteristic techniques like “X-ray diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive x ray spectroscopy (EDX), Fourier-transform infrared spectroscopy (FTIR), Brunauer Emmett Teller analysis (BET), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy” are applied to investigate the properties of prepared materials. Electrochemical techniques “Linear sweep voltammetry (LSV), Cyclic voltammetry (CV), Electrochemical impedance spectroscopy (EIS), and Chronopotentiometry” are applied to measure the effectiveness of the catalyst. In the first series, ZIF-67 MOF and 1,3,5,6,8 wt. % composites of g-C3N4 @ZIF 67 have been synthesized. From the designed series, 3wt% g-C3N4@ZIF-67 composite needed less overpotential for OER (200 mV) and HER (-176 mV) with the stability test for 24 hrs. In the second part of the work, ZIF-67-derived CoS2 and 1,3,5,8wt% composites with MWCNT have been synthesized The synthesized catalyst series demonstrates prominent activity for electrochemical water-splitting applications. Among series, 5wt% MWCNT@CoS2 composite needed low overpotential -153 mV for “Hydrogen Evolution Reaction and 186 mV for Oxygen Evolution Reaction”. The optimized catalyst demonstrated remarkable stability, maintaining its efficacy for 40 hours. In the third phase of our research, the catalyst was modified with reduced graphene oxide (rGO) to form Fe-Co/C@rGO. Among the series, the 5wt% composite (rGO@Fe Co/NC) outstandingly performed with less requisite extrapotential values; -148 and 120mV for “Hydrogen and Oxygen evolution reaction”. Meanwhile, the composite catalyst maintained stability for 24 hour deprived of significant degradation