We report the very first example of a catalyst based on a ternary composite of graphitic carbonitride (g‐C3N4), ceria (CeO2) and magnetite (Fe3O4) for overall water splitting in 1.0 M KOH. Synergy between the components due to electronic effects results in a highly efficient catalyst which catalyzes Oxygen Evolution Reaction (OER) and Hydrogen Evolution Reaction (HER) at substantially low overpotentials (400 mV and 310 mV respectively) to produce benchmark current density (10 mA cm−2). OER activity of the catalysts surpasses that of the benchmark RuO2 catalyst at higher current densities (≥50 mA cm−2). The composite catalyst is stable and shows a Faraday efficiency of 98 % for OER. Overall water splitting was achieved at an overpotential of 1.94 V which is substantially high at 1 wt % loading of active metal.

Visible light active g- C 3 N 4(0.94) /CeO 2(0.05) /Fe 3 O 4(0.01) ternary composite nanosheets were fabricated by facile co-precipitation routes. The density functional theory (DFT) computations investigated changes in geometry and electronic character of g-C 3 N 4 with CeO 2 and Fe 3 O 4 addition. Chemical and surface characterizations were explored with XRD, XPS, SEM, TEM, PL, DRS and Raman measurements. DRS and PL spectroscopy evidenced the energy band gap tailoring from 2.68 eV for bulk g-C 3 N 4 and 2.92 eV for CeO 2 to 2.45 eV for the ternary nanocomposite. Efficient electron/hole pair separation, increase in red-ox species and high exploitation of solar spectrum due to band gap tailoring lead to higher degradation efficiency of g- C 3 N 4(0.94) /CeO 2(0.05) /Fe 3 O 4(0.01) . Superior sun light photocatalytic breakdown of 2-Chlorophenol was observed with g-C 3 N 4 having CeO 2 loading up to 5 wt%. In case of ternary nanocomposites deposition of 1 wt% Fe 3 O 4 over g-C 3 N 4 /CeO 2 binary composite not only showed increment in visible light catalysis as predicted by the DFT studies, but also facilitated magnetic recovery. The g- C 3 N 4(0.94) /CeO 2(0.05) /Fe 3 O 4(0.01) nanosheets showed complete mineralization of 25 mg.L −1 2-CP (aq) within 180 min exposure to visible portion of sun light and retained its high activity for 3 consecutive reuse cycles. The free radical scavenging showed superoxide ions and holes played a significant role compared to hydroxyl free radicals while chromatographic studies helped establish the 2-CP degradation mechanism. The kinetics investigations revealed 2.55 and 4.04 times increased rate of reactions compared to pristine Fe 3 O 4 and CeO 2 , showing highest rate constant value of 18.2 × 10 −3 min −1 for the ternary nanocomposite. We present very persuasive results that can be beneficial for exploration of further potential of g-C 3 N 4(0.94) /CeO 2(0.05) /Fe 3 ...

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