Photoelectrochemical Studies on Metal-Doped Graphitic Carbon Nitride Nanostructures under Visible-Light Illumination

Abstract

Recently, the engineering of optical bandgaps and morphological properties of graphitic carbon nitride (g-C3N4) has attracted significant research attention for photoelectrodes and environmental remediation owing to its low-cost synthesis, availability of raw materials, and thermal physical–chemical stability. However, the photoelectrochemical activity of g-C3N4-based photoelectrodes is considerably poor due to their high electron–hole recombination rate, poor conductivity, low quantum efficiency, and active catalytic sites. Synthesized Ni metal-doped g-C3N4 nanostructures can improve the light absorption property and considerably increase the electron–hole separation and charge transfer kinetics, thereby initiating exceptionally enhanced photoelectrochemical activity under visible-light irradiation. In the present study, Ni dopant material was found to evince a significant effect on the structural, morphological, and optical properties of g-C3N4 nanostructures. The optical bandgap of the synthesized photoelectrodes was varied from 2.53 to 2.18 eV with increasing Ni dopant concentration. The optimized 0.4 mol% Ni-doped g-C3N4 photoelectrode showed a noticeably improved six-fold photocurrent density compared to pure g-C3N4. The significant improvement in photoanode performance is attributable to the synergistic effects of enriched light absorption, enhanced charge transfer kinetics, photoelectrode/aqueous electrolyte interface, and additional active catalytic sites for photoelectrochemical activity.

Influence of Cocatalysts (Ni, Co, and Cu) and Synthesis Method on the Photocatalytic Activity of Exfoliated Graphitic Carbon Nitride for Hydrogen Production

“…The two peaks at 862.5 and 876.8 eV are satellite peaks of Ni 2+ . Ni always showed strong satellite peaks approximately 6 eV above the main electronic lines [31,[43][44][45][46][47]. The XPS peaks of cobalt and copper loaded ex-g-CN (Figure S6) confirmed the presence of these species in different oxidation states.…”

Self‐Propelled Magnetic Dendrite‐Shaped Microrobots for Photodynamic Prostate Cancer Therapy

“…To elucidate the photocatalytic activity of hematite microrobots upon light exposure, the mixed potential was measured from the Tafel plot of the hematite microrobots under dark/light circumstances in water. As shown in Figure 2C, the mixed potential of hematite transfers to a more negative value with light exposure, which shows a difference of 40 mV between dark and light, indicating that hematite microrobots generated electron‐hole pairs under light irradiation [37] . The speed of microrobots in pure water was merely 2.5±0.5 μm s −1 , but it progressively increased to 18±5 μm s −1 when a higher concentration of H 2 O 2 solution was introduced (Figure 2D).…”

“…As shown in Figure 2C, the mixed potential of hematite transfers to a more negative value with light exposure, which shows a difference of 40 mV between dark and light, indicating that hematite microrobots generated electron-hole pairs under light irradiation. [37] The speed of microrobots in pure water was merely 2.5 � 0.5 μm s À 1 , but it progressively increased to 18 � 5 μm s À 1 when a higher concentration of H 2 O 2 solution was introduced (Figure 2D). Photocatalytic decomposition of H 2 O 2 proceeds according to the reaction scheme in Equation ( 1): [32] a-Fe…”