ZIF-67anchored on sulfur-doped carbon nitride as oxygen evolution electrocatalysts

Abstract

MOF materials can change their electrical conductivity and structural properties by forming a hybrid with graphite carbon nitride (g-C₃N₄), and can be considered for energy conversion and storage technologies as an interesting class of functional materials and precursors of inorganic materials. In this work, nano-hybrids based on ZIF-67 with sulfur-doped carbon nitride were fabricated. g-C₃N₄ was first synthesized by pyrolyzing urea, then g-C₃N₄/ZIF-67 was formed by hydrothermal technique, and finally it was modified with thioacetamide (TAA) to transform into S-g-C₃N₄/ZIF-67 catalytic material with higher electrochemical active surface area. The mass ratio of ZIF-67 to g-C₃N₄ and g-C₃N₄/ZIF-67 to TAA as well as hydrothermal temperature were investigated by linear sweep voltammetry in order to screen the optimal composite material for oxygen evolution reaction (OER). When the doping amount of g-C₃N₄ in ZIF-67 was 50 mg (the mass ratio of Co(NO₃)₂⸱6H₂O to g-C₃N₄ was 25:1), that of TAA was 20 mg (the mass ratio of g- C₃N₄/ZIF-67 to TAA was 3:2), and the hydrothermal reaction was at 150 °C for 2 h, the prepared composite exhibited the lowest overpotential (289 mV). I-t test and cyclic voltammetry cycle also proved that S-g-C₃N₄/ZIF-67 (150 °C) has relatively good stability. Therefore, sulfur-doped carbon nitride supported ZIF-67 composite can expose more active sites, improve the conduction efficiency and ion transport capacity, and accelerate the process of OER kinetics, which provides a new way for the preparation of ZIF-67 derivatives for OER catalysts.