A boronization-induced amorphous-crystalline interface on a Prussian blue analogue for efficient and stable seawater splitting

Unleashing the room temperature boronization: Blooming of Ni-ZIF nanobuds for efficient photo/electro catalysis of water

Water splitting provides an environmental-friendly and sustainable approach for generating hydrogen fuel. The inherent energetic barrier in two-core half reactions such as the Hydrogen Evolution Reaction (HER) and Oxygen Evolution Reaction (OER) leads to undesired increased overpotential and constrained reaction kinetics. These challenges pose significant challenges that demand innovative solutions to overcome. One of the efficient ways to address this issue is tailoring the morphology and crystal structure of metal-organic frameworks (MOF). Nickel Zeolite Imidazolate Framework (Ni-ZIF) is a popular MOF and it can be tailored using facile chemical methods to unleash a remarkable bifunctional electro/photo catalyst. This innovative solution holds the capability to address prevailing obstacles such as inadequate electrical conductivity and limited access to active metal centers due to the influence of organic ligands. Thereby, applying boronization to the Ni-ZIF under different duration, one can induce blooming of nanobuds under room temperature and modify oxygen vacancies in order to achieve higher reaction kinetics in electro/photo catalysis. It can be evidenced by the 24-h boronized Ni-ZIF (BNZ), exhibiting lower overpotentials as electrocatalyst (OER-396 mV & HER-174 mV @ 20 mA/cm2) in 1 M KOH electrolyte and augmented gas evolution rates when employed as a photocatalyst (Hydrogen-14.37 μmol g-1min-1 & Oxygen-7.40 μmol g-1min-1). The 24-h boronization is identified as the optimum stage of crystalline to amorphous transformation which provided crystalline/amorphous boundaries as portrayed by X-Ray diffraction (XRD) and High Resolution-Transmission Electron Microscopy (HR-TEM) analysis. The flower-like transformation of 24-BNZ, characterized by crystalline-amorphous boundaries initiates with partial disruption of Ni-N bonds and formation of Ni-B bonds as evident from X-ray Photoelectron Spectroscopy (XPS). Further, the 24-h BNZ exhibit bifunctional catalytic activities with pre-longed stability. Overall, this work presents a comprehensive study of the electrocatalytic and photocatalytic water splitting properties of the tailored Ni-ZIF material.

Ruthenium Oxide Nanoparticles Immobilized on Ti3C2 MXene Nanosheets for Boosting Seawater Electrolysis

Seawater electrolysis represents a viable alternative for large-scale synthesis of hydrogen (H2), which is recognized as the most promising clean energy source, without relying on scarce fresh water. However, high energy cost and harmful chlorine chemistry in seawater limited its development. Herein, an effective catalyst based on a ruthenium nanoparticle-Ti3C2 MXene composite loaded on nickel foam (RuO2-Ti3C2/NF) with an open, fine, and homogeneous nanostructure was devised and synthesized by electrodeposition for high performance and stable overall seawater splitting. To drive a current density of 100 mA cm-2, the RuO2-Ti3C2/NF electrode required a small overpotential of 85 and 351 mV for HER and OER in 1 M KOH with only a slight increase in 1 M KOH seawater (156 and 378 mV for, respectively, HER and OER). An assembled RuO2-Ti3C2/NF-based two-electrode cell required an overpotential of only 1.84 V to acquire 100 mA cm-2 in 1 M KOH seawater and maintained its activity for over 25 h. This low cell voltage effectively prevented chlorine electrochemical evolution without anode protection. These promising results open up new avenues for the effective conversion of abundant seawater resources to hydrogen fuel.