S-scheme heterojunctions have emerged as an innovative alternative to the traditional type-II and Z-scheme counterparts, overcoming challenges in sustaining an efficient redox power and adequate spatial charge carrier separation. Such heterojunctions integrate semiconductors with the aligned or partially overlapped energy levels, enhancing charge transfer and separation for improved light-induced redox reactions. Utilizing a facile combined ultra-sonication and calcination approach, graphitic carbon nitride (g-C3N4/gCN) as the reducing photocatalyst (RP) and two- or three-dimensional perovskites as the oxidizing photocatalyst (OP) have been used for the synthesis of S-scheme heterojunctions. Leveraging the superior light absorption capability of gCN, its highly negative conduction band (CB), and the suitable band gap and chemical stability of perovskites, these photocatalysts are uniquely tailored to create S-scheme heterojunction. Upon light irradiation, the heterojunctions release strong photogenerated electrons, facilitating water splitting reaction to produce H2 and the photofixation of N2 to produce aqueous ammonia. Dual S-scheme heterojunctions are emerging and should be studied for an improved photocatalytic performance.