Annealing environment on the photoelectrochemical water oxidation and electrochemical supercapacitor

What is it about?

SnO2 quantum dots (SQD) were prepared by utilizing the soft-chemical approach. The formed SQD's were annealed in two kinds of environments: air and nitrogen (N2). Each annealing environment resulted in significant improvement in the performance of water oxidation and electrochemical supercapacitor performance. The specific capacitance of the SQD's under the N2 annealing process (SQD-N2) shows significantly better electrochemical performance. A specific capacitance of 79.13 F/g was achieved for SQD-N2 sample by applying a current of 1 mA, which was approximately 1.5 times greater than that of the pristine SQD's. A cycle stability of 99.4% over 5000 cycles was achieved by SQD-N2. The process of nitrogen annealing environment brings down the bandgap from 3.37 to 1.9 eV. The SQD-N2 sample shows the highest photocurrent over SQD and SQD-Air samples. From the LSV study, SQD-N2 shows the photocurrent density of 4.82 mA/cm2, which is 1.43 times greater than pristine SQD sample. The nitrogen-annealing environment provides the optimal environment to tune the average crystallite size and crystallinity nature of SQD's to improve the optical properties like bandgap to enhance the water oxidation and also electrochemical performance.

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Why is it important?

The nitrogen-annealing environment provides the optimal environment to tune the average crystallite size and crystallinity nature of SQD's to improve the optical properties like bandgap to enhance the water oxidation and also electrochemical performance.The energy demand across the globe is enormously increasing day by day due high population growth and to drive the industries and the economy. Solar energy is considered to be the best environmentally friendly and everlasting availability resource for the mankind (Kadam et al., 2021; Nehra et al., 2020). Photoelectrochemical water splitting provides an environmental friendly solution to generate the renewable energy in the form of hydrogen (Barzgar Vishlaghi et al., 2021; Reddy et al., 2021). SnO2 is a wide bandgap semiconductor with good electrical properties and chemical properties with non-toxic nature. Due to its wide bandgap of ～3.5 eV, it absorbs only UV light which was further restricted the PEC performance (Bai et al., 2021). In order to reduce bandgap of SnO2, various strategies like doping with transition metals were adopted to decrease the bandgap to harvest visible light.

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