Well-designed bio-based waste sewage sludge (WSS) cocatalyst coupled g-C3N4 nanorods with the synergistic effect of sludge metals (M=Ni, Cu, Al, Mn) to construct ternary heterojunction for solar H2 production

A ternary heterojunction of waste sewage sludge (WSS) as a co-catalyst with sludge metals (M = Ni, Cu, Zn, Mn, and Fe) elements anchored over g-C3N4 nanorods (g-CNNR) was fabricated for photocatalytic H2 evolution under visible light. The innovative WSS enables H2 production of 25 μmol h−1 g−1 due to the presence of oxidized (Fe2O3, ZnO) and other metals to promote charge carrier separation. The g-CNNR with WSS provides good interface interaction with proficient charge carrier separation and can potentially enhance photocatalytic activity, as confirmed by standard metal elements. Using a 10% WSS/g-CNNR nanotexture, a maximum H2 yield of 195 μmol h−1 g−1 was achieved, 4.5 and 7.8 times higher than pure g-CNNR and WSS, respectively. The finding reveals that adding WSS significantly increases the photocatalytic H2 generation under visible light. This noticeable improvement was caused by the formation of heterojunction, which separated charge carriers, higher visible light absorption and synergistic effects of multiple elements in WSS which contributed to promote solar hydrogen evolution. Furthermore, the ultrasonic approach was found promising to enhance H2 evolution approximately two-fold than of bulk WSS/g-CNNR due to more light penetration and separation of charge carriers. Among the sacrificial reagents, methanol enables a higher yield of H2 with more stability in multiple cycles. The findings of this work would be beneficial for further investigation on the use of WSS as a cocatalyst and support in different energy and environment applications.