Date-palm syrup/g-C3N4: A metal/non-metal synergistic composite for hydrogen production via seawater splitting

• Date palm syrup (DPS)/g-C 3 N 4 composite was synthesized using a facile technique. • DPS/g-C 3 N 4 composite exhibited higher hydrogen yields in seawater compared to deionized water. • Co-doping with S, Co, Mn, Cu narrowed band gap and extended light absorption. • DPS prevented chloride ion oxidation, enhancing hydrogen evolution in seawater. • DPS provides sustainable strategy using for seawater splitting and stable over five cycles. Efficient photocatalyst development is crucial for hydrogen production. Sustainable strategies utilizing seawater and metal- and non-metal-rich date palm components provide eco-friendly energy solutions. Herein, graphitic carbon nitride (g-C 3 N 4 ) was combined with date palm syrup (DPS) to create a novel composite for hydrogen production via water and simulated seawater splitting. The study investigated the effects of various sacrificial agents, their concentrations, and the NaCl content in simulated seawater on hydrogen evolution. The 50 % DPS/g-C 3 N 4 composite demonstrated an optimal hydrogen yield of 7434.6 μmol g −1 in deionized water, a two-order-of-magnitude improvement over pristine g-C 3 N 4 . DPS incorporation led to the doping of cobalt, copper and manganese in the g-C 3 N 4 resulting in a narrower band gap, extended light absorption, and suppressed recombination of photoexcited electron-hole pairs. Remarkably, the 50 % DPS/g-C 3 N 4 composite exhibited even higher hydrogen yields in simulated seawater splitting. In the absence of sacrificial agents, deionized water produced 637.98 μmol g −1 of hydrogen after 80 min of light exposure, whereas simulated seawater with 3.5 wt% NaCl yielded 1739.12 μmol g −1 under the same conditions. The ions in simulated seawater facilitated electron transfer, while sulfur from DPS prevented chloride ion oxidation and deposition on the catalyst surface, enhancing the reduction reaction and hydrogen evolution. This work introduces a sustainable strategy to modify g-C 3 N 4 for enhanced photocatalytic hydrogen production using deionized water and simulated seawater.