Oxygen vacancy engineering in MXenes for sustainable electrochemical energy conversion and storage applications†
Abstract
Ever-increasing global energy requirements and environmental pollution have directed major research focus on developing sustainable energy conversion and energy storage technologies. Ti3C2TX MXenes are widely considered a potential electrode material for electrochemical hydrogen energy generation through water splitting and electrochemical energy storage supercapacitor applications. Herein, multifunctional Ti3C2TX MXene-based nanocomposites with varying Eu2O3 concentrations were synthesized and systematically investigated for electro/photocatalytic water splitting and two-electrode supercapacitor properties. Ti3C2TX MXenes exhibit high electrical conductivity, tunable surface functionalities and multivalent Ti oxidation states. Meanwhile, the incorporation of Eu2O3 supplements the electrochemical performance by altering the physio-chemical structure and overcoming the intersheet restacking and oxidative degradation issues of pristine Ti3C2TX MXenes. More importantly, the interfacial charge transfer synergism between Ti3C2TX MXenes and Eu2O3 creates oxygen vacancies that modulate the electronic structure of nanocomposites, aiding in the formation of abundant hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) sites, photo-generated charge trapping centres and pseudocapacitive sites. The key findings of the present study showed that the Eu2O3/MXene nanocomposite with an optimum oxygen vacancy content exhibited excellent performance with a small overpotential of 63 mV and 169 mV and a high faradaic efficiency of 96.2% and 95.23% to drive the HER and OER, respectively. Additionally, upon combination with CdS as the photoabsorber, the optimized nanocomposite achieved a high photocurrent density of 4.86 mA cm−2, leading to a H2 evolution rate of 56.67 μL min−1. Considering supercapacitor characteristics, the optimized nanocomposite exhibited a high specific capacitance of 374.98 F g−1 with an energy density and power density of 13.02 Wh kg−1 and 300 W kg−1, respectively. Thus, the results of the present study establish a facile approach to develop high-performance multifunctional electrodes for advancing electrochemical energy conversion and storage technologies.
- This article is part of the themed collection: Engineering soft materials for healthcare, energy and environment