Abstract
Oxygen evolution reaction (OER) is a pivotal step for many sustainable energy technologies, and exploring inexpensive and highly efficient electrocatalysts is one of the most crucial but challenging issues to overcome the sluggish kinetics and high overpotentials during OER. Among the numerous electrocatalysts, metal-organic frameworks (MOFs) have emerged as promising due to their high specific surface area, tunable porosity, and diversity of metal centers and functional groups. It is believed that combining MOFs with conductive nanostructures could significantly improve their catalytic activities. In this study, an MXene supported CoNi-ZIF-67 hybrid (CoNi-ZIF-67@Ti3C2Tx) was synthesized through the in-situ growth of bimetallic CoNi-ZIF-67 rhombic dodecahedrons on the Ti3C2Tx matrix via a coprecipitation reaction. It is revealed that the inclusion of the MXene matrix not only produces smaller CoNi-ZIF-67 particles, but also increases the average oxidation of Co/Ni elements, endowing the CoNi-ZIF-67@Ti3C2Tx as an excellent OER electrocatalyst. The effective synergy of the electrochemically active CoNi-ZIF-67 phase and highly conductive MXene support prompts the hybrid to process a superior OER catalytic activity with a low onset potential (275 mV vs. a reversible hydrogen electrode, RHE) and Tafel slope (65.1 mV∙dec−1), much better than the IrO2 catalysts and the pure CoNi-ZIF-67. This work may pave a new way for developing efficient non-precious metal catalyst materials.
Highlights
With the rapid combustion of fossil fuels and the ever-growing concerns relating to the environmental crisis, developing sustainable energy technologies has triggered extensive attention [1]
Considering the negatively charged Ti3C2Tx surface due to the presence of numerous surface termination groups (e.g., –O, –OH, and –F) introduced during the etching process, Co2+ and Ni2+ ions could be adsorbed on these termination group sites by electrostatic interaction, and could in-situ synthesize CoNi-ZIF-67 rhombic dodecahedrons on the surface and between the interlayers of Ti3C2Tx
A MXene supported CoNi-ZIF-67 hybrid was synthesized via the in-situ growth of CoNi-ZIF-67 rhombic dodecahedrons on the Ti3C2Tx matrix via a coprecipitation reaction
Summary
With the rapid combustion of fossil fuels and the ever-growing concerns relating to the environmental crisis, developing sustainable energy technologies (such as metal-air batteries and water splitting) has triggered extensive attention [1]. Highly active electrocatalysts are required to increase the reaction rate and to lower the overpotentials in the OER process. The precious metal oxides (e.g., RuO2 and IrO2) are the best electrocatalysts with a promoted proton-coupled charge transfer process, but their scale-up implementation has been greatly hampered by their high price, scarcity and poor durability [3,4]. Within this context, increasing efforts have been devoted to the exploration of inexpensive, earth-abundant and highly efficient electrocatalysts for OER [5]. The earth-based transition metal-rich compounds, including transition metal oxides [3], sulfides [6] and phosphides [7], have exhibited great promise as OER electrocatalysts
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