Efficient Photoelectrochemical Performance of Gamma Irradiated gC3N4 and its g-C3N4@BiVO4 Heterojunction for Solar Water Splitting

This is the author accepted manuscript. The final version is available from the American Chemical Society via the DOI in this recordComprehensive experimental and density functional theory simulations have been performed for the enhanced photoelectrochemical performance of gamma irradiated g-C3N4 and its heterojunction with BiVO4. The structure and morphology of g-C3N4@BiVO4 as a heterojunction were analyzed and verified from the correlation of experimental and theoretical data. It is found that gamma radiations have changed the bonding structure of g-C3N4 which ultimately reduces the optical bandgap energy. Moreover, the performance of gamma-irradiated g-C3N4 is two-fold, compared to that of non-irradiated one; increases from 3.59 to 5.86 µAcm-2 at 1.23 V versus Ag/AgCl in 0.5 M Na2SO4 electrolyte solution (pH 7). Finally, it is observed that the performance of gamma irradiated g-C3N4 in g-C3N4@BiVO4 heterojunction increased from 0.53 mA cm-2 to 1.38 mA cm-2, compared to that of the non–irradiated one. In summary, it has been concluded that gamma-irradiated g-C3N4 and its heterojunction is potentially be applied in PEC solar water splitting.National University of Malaysi

Fabrication of exfoliated graphitic carbon nitride, (g-C<inf>3</inf>N<inf>4</inf>) thin film by methanolic dispersion

This paper reports the successful exfoliation of nanosheets from bulk g-C N by using urea as a precursor. The alteration from bulk g-C N powder, changed its semiconductor arrangements such as the optical absorption, chemical bonding, and topography images. A slow direct low thermal treatment (∼40 °C, 24 h) was proposed as a formation of a thinner layer by layer, complete and effective polymerization for an exfoliated g-C N . The photocurrent responses were more than two times higher for exfoliated g-C N compared with bulk g-C N , reaching ∼4.37 μA cm up to 10.21 μA cm at 1.23 vs. (Ag/AgCl). This fabrication method involved dispersing of the highly stable g-C N suspension onto FTO surface via spin coating, followed by a moderate post-annealing temperature at 350 °C. The monolayer g-C N act as a photoelectrode, responding to light and dark current, and maintained its own intrinsic n-types properties. The interaction of the C and N atom with molecules of methanol (CH OH) followed with vibration force (ultrasonication) produces the ultrafast drying and can transmit to disrupt the van der Waals forces within the g-C N structure. Therefore, due to the ability the good performance, the exfoliated g-C N can be envisioned as a potential application such as water splitting, solar cell, and environmental remediation. 3 4 3 4 3 4 3 4 3 4 3 4 3 4 3 3 4 3 4 −2 −

Enhanced photoelectrochemical performance of Z-scheme g-C3N4/BiVO4 photocatalyst

This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this record.BiVO 4 is a considerably promising semiconductor for photoelectrochemical water splitting due to its stability, low cost and moderate band gap. In this research, g-C 3 N 4 was proposed in Z-scheme configuration which boosted the performance of BiVO 4 up to four times. The experimental observations were counterchecked with Density Functional Theory (DFT) simulations. A TiO 2 /BiVO 4 heterojunction was developed and its performance was compared with that of g-C 3 N 4 /BiVO 4 . The photocurrent for g-C 3 N 4 /BiVO 4 was 0.42 mAcm −2 at 1.23 V vs. RHE which was the highest among g-C 3 N 4 based Z-scheme heterojunction devices. Lower charge transfer resistance, higher light absorption and more oxygen vacancy sites were observed for the g-C 3 N 4 based heterojunction. The simulated results attested that g-C 3 N 4 and BiVO 4 formed a van der Waals type heterojunction, where an internal electric field facilitated the separation of electron/hole pair at g-C 3 N 4 /BiVO 4 interface which further restrained the carrier recombination. Both the va lence and conduction band edge positions of g-C 3 N 4 and BiVO 4 changed with the Fermi energy level. The resulted heterojunction had small effective masses of electrons (0.01 m e ) and holes (0.10 m e ) with ideal band edge positions where both CBM and VBM were well above and below the redox potential of water.The authors would like to acknowledge financial support from Universiti Kebangsaan Malaysia through internal grant GUP-2016-089 and also for providing facilities to perform this research. H.U. acknowledges the supercomputing facilities of ESI Beowulf Cluster, University of Exeter, UK