Synthesis and characterization of electrocatalysts based on boron and earth-abundant transition metals for electrochemical water splitting

As the world grapples with growing environmental challenges and an ever-‎expanding population, the need for a sustainable alternative to fossil fuels has become ‎an unprecedented challenge. The quest for sustainable energy production strategies has ‎converged on the electrocatalytic water splitting process integrated with renewable ‎energy resources. The successful realization of this process hinges on the development ‎of competent, cost-effective, and earth-abundant electrocatalysts capable of driving ‎both the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) ‎efficiently within the same electrolyte.‎ Over the course of four years of research, this PhD thesis has dedicated extensive ‎efforts to address this challenge by investigating novel electrocatalysts. The following ‎key contributions have been made. 1) Novel Electrocatalysts: Synthesis, ‎characterization, and electrochemical evaluation of newfangled electrocatalysts with ‎the formal composition of Mg1−xTMxB2 (x = 0.025, 0.05, and 0.1; TM = Fe and Co). The ‎study primarily focuses on their performance in both HER and OER under 1.0 M KOH ‎medium. Among these catalysts, Mg0.95Co0.05B2 has demonstrated exceptional HER ‎performance, boasting an overpotential of 470 mV at 10 mA cm−2. The findings ‎suggest a promising direction in the development of highly competent and low-cost ‎electrocatalysts. 2) Transformative Materials: Development of electrocatalysts with a ‎formal composition of V1–xCoxB2 (x = 0, 0.05, 0.1, and 0.2) for use in the oxygen-‎evolving reaction. The incorporation of Co into the VB2 structure has led to a dramatic ‎transformation in morphology, reducing the overpotential to 200 mV at 10 mA cm−2. ‎This performance rivals that of the noble-metal catalyst RuO2 (290 mV) and ‎demonstrates notable durability under 1.0 M KOH conditions. 3) Metal Organic ‎Frameworks (MOFs): Exploration of nanocomposites based on NCM [N = Ni, C = ‎Co, M = Fe, Cu, Zn]/Ni-BDC@NF, directly developed on nickel foam (NF), revealing ‎unique electronic structure modulation. Notably, the NCF/Ni-BDC catalyst ‎demonstrates outstanding OER performance, requiring only 1.35 V versus a reversible ‎hydrogen electrode (RHE) to achieve 10 mA cm–2 current density. This research ‎showcases the potential of 2D MOFs as versatile materials for efficient water splitting. ‎‎4) Heterostructures: Presentation of a high-performance and durable heterostructure ‎of NiMo/CoMoO4 for the alkaline HER, constructed via a two-pot in situ growth ‎strategy on a NF. The heterostructure exhibits low overpotential (102 mV at 10 mA ‎cm–2) and high Faradaic efficiency. It highlights the synergy of metallic and oxide ‎components, demonstrating superior performance in the HER, a crucial element of ‎water electrolysis for carbon-neutral hydrogen production. 5) MOF-Derived ‎Catalysts: Introduction of a nanostructured interface between NiMo/CuO@C derived ‎from Cu-MOF, designed and developed on NF, as a competent HER electrocatalyst in ‎alkaline media. This catalyst shows a low overpotential of 85 mV at 10 mA cm−2, ‎rivalling Pt/C, and exhibits remarkable durability over an extended period of 50 h.‎ This four-year research endeavor culminates in a comprehensive understanding of ‎advanced electrocatalysts for sustainable water splitting. The thesis underscores the ‎significance of these materials in addressing the global need for clean and efficient ‎hydrogen production, offering a pathway towards a more sustainable and eco-friendly ‎energy future.‎