Advances in modifications of Ag/g-C3N4 for stable and effective photoanode for OER

Abstract

Silver (Ag) incorporated graphitic carbon nitride (g-C3N4) nano-composites having various ratios of Ag were prepared via a chemical route. The synthesized catalysts were potentially employed in an oxygen evolution reaction (OER) through photoelectrochemical (PEC). An XRD profile of Ag/g-C3N4 nano-composite depicted hexagonal g-C3N4 along with FCC Ag presence. The inhomogeneous distribution of tiny Ag nanospheres on irregularly agglomerated sheets of g-C3N4 was clearly seen in SEM images. The elemental mapping provided distribution of elements in the composite sample. Ag/g-C3N4 nano-composite samples show improvement in absorption edge with a reduction in band gap energy. FTIR studies illustrated strong surface interaction among Ag and g-C3N4 nano-sheets. The prominent reduction in PL peaks intensity for B30 Ag/g-C3N4 nano-composite suggested a long lifetime of photo induced charge carriers. XPS analysis confirmed the existence of metallic Ag on g-C3N4. B30 Ag/g-C3N4 attained better PEC activity results as compared to all other prepared photocatalysts. In OER experiments, B30 Ag/g-C3N4 showed a small onset potential (0.33 V) leading to more production of photo excited electrons and a reduction in photo generated electron-hole recombination process. The improved Jsc and Voc of B30 Ag/g-C3N4 indicated the shorter lifetime of charge carriers across electrode and electrolyte interface through suitable charge separation. Optimized B30 Ag/g-C3N4 is active and steady for efficient PEC water splitting in comparison to other prepared nanosystems.