Designing In Situ Grown Ternary Oxide/2D Ni-BDC MOF Nanocomposites on Nickel Foam as Efficient Electrocatalysts for Electrochemical Water Splitting

Ebrahim Sadeghi; Naeimeh Sadat Peighambardoust; Sanaz Chamani; Umut Aydemir

doi:10.1021/acsmaterialsau.2c00073

Designing In Situ Grown Ternary Oxide/2D Ni-BDC MOF Nanocomposites on Nickel Foam as Efficient Electrocatalysts for Electrochemical Water Splitting

ACS Mater Au. 2022 Dec 28;3(2):143-163. doi: 10.1021/acsmaterialsau.2c00073. eCollection 2023 Mar 8.

Authors

Ebrahim Sadeghi^{1

2}, Naeimeh Sadat Peighambardoust¹, Sanaz Chamani¹, Umut Aydemir^{1

3}

Affiliations

¹ Koç University Boron and Advanced Materials Applications and Research Center (KUBAM), Sariyer, Istanbul34450, Turkey.
² Graduate School of Sciences and Engineering, Koç University, Sariyer, Istanbul34450, Turkey.
³ Department of Chemistry, Koç University, Sariyer, Istanbul34450, Turkey.

Abstract

The security of future energy, hydrogen, is subject to designing high-performance, stable, and low-cost electrocatalysts for hydrogen and oxygen evolution reactions (HERs and OERs), for the realization of efficient overall water splitting. Two-dimensional (2D) metal-organic frameworks (MOFs) introduce a large family of materials with versatile chemical and structural features for a variety of applications, such as supercapacitors, gas storage, and water splitting. Herein, a series of nanocomposites based on NCM/Ni-BDC@NF (N=Ni, C=Co, M:F=Fe, C=Cu, and Z=Zn, BDC: benzene dicarboxylic acid, NF: nickel foam) were directly developed on NF using a facile yet scalable solvothermal method. After coupling, the electronic structure of metallic atoms was well-modulated. Based on the XPS results, for the NCF/Ni-BDC, cationic atoms shifted to higher oxidation states, favorable for the OER. Conversely, for the NCZ/Ni-BDC and NCC/Ni-BDC nanocomposites, cationic atoms shifted to lower oxidation states, advantageous for the HER. The as-prepared NCF/Ni-BDC demonstrated prominent OER performance, requiring only 1.35 and 1.68 V versus a reversible hydrogen electrode to afford 10 and 50 mA cm^-2 current densities, respectively. On the cathodic side, NCZ/Ni-BDC exhibited the best HER activity with an overpotential of 170 and 350 mV to generate 10 and 50 mA cm^-2, respectively, under 1.0 M KOH medium. In a two-electrode alkaline electrolyzer, the assembled NCZ/Ni-BDC (cathode) ∥ NCF/Ni-BDC (anode) couple demanded a cell voltage of only 1.58 V to produce 10 mA cm^-2. The stability of NCF/Ni-BDC toward OER was also exemplary, experiencing a continuous operation at 10, 20, and 50 mA cm^-2 for nearly 45 h. Surprisingly, the overpotential after OER stability at 50 mA cm^-2 dropped drastically from 450 to 200 mV. Finally, the faradaic efficiencies for the overall water splitting revealed the respective values of 100 and 85% for the H₂ and O₂ production at a constant current density of 20 mA cm^-2.