Dark Current Water Splitting Employing Ni3TeO6 as a Photocharged Photoelectrocatalyst

• Published in: Physica status solidi. A, Applications and materials science Applications and materials science, 2023-06, Vol.220 (12), p.n/a
• Main Authors: Iqbal, Mohd Zafar, Carleschi, Emanuela, Doyle, Bryan Patrick, Kriek, Roelof Jacobus
• Format: Article
• Language: English
• Subjects: Charge transfer; Dark current; Electrical measurement; Electrolytes; Illumination; Oxidation; oxygen evolution reaction; photocharging; Photoelectric effect; photoelectrocatalyst; Storage capacity; Time constant; Water splitting
• ISSN: 1862-6300; 1862-6319
• DOI: 10.1002/pssa.202300002

Herein, the photoelectrocatalytic and photocharging activity of a Ni3TeO6 (NTO‐700) photoelectrocatalyst for water oxidation in alkaline medium is demonstrated and calcined at 700 °C. The photoelectrocatalytic (PEC) activity of the sample is increased upon an increase in the illumination time. With a twofold increase in photocurrent density at 1.8 V, the PEC 150 sample (having been illuminated for 150 min) attained the highest PEC activity. The synthesized material has displayed an excellent charge storage capacity in KOH and Na2SO4 electrolyte solutions (both 0.1 m). The chrono‐amperometry measurement, subsequent to light interruption, has sustained almost 44% higher current density (even after 200 min) compared to the pure electrocatalytic baseline in a Na2SO4 electrolyte. The charge transfer resistance, Rct, decreases from 633.40 to 170.40 Ω, while the charge transfer rate constant, kct, increases from 7.93 to 27.03 s−1, as a function of illumination time. This points to fast separation of electron–hole (e−–h+) pairs and a slower recombination rate. The lower values of the charge transfer resistance and the time constant recorded for the light interrupted samples, as compared to the electrochemical sample, are attributed to the stored charge that drives water oxidation at a higher rate. Employing Ni3TeO6 as a photoelectrocatalytic semiconductor, the production of hydrogen through water electrolysis can not only be enhanced but also sustained in the dark after an initial period of photocharging. This photoinduced enhancement of the oxygen evolution reaction (OER) and sustained dark OER current coincides with an increase in the charge transfer rate constant (kct).