N, S, P co-doped Co/Co3O4/C particles on carbon fiber paper as a self-supported bifunctional catalyst for direct seawater splitting

To optimize the distribution and transportation of electrical energy, converting surplus or low-quality electricity through electrocatalytic seawater splitting to produce hydrogen is an ideal method. In this work, we developed a bifunctional electrocatalyst (ZIF-9/CP-S-P) through the in-situ growth of ZIF-9 on the carbon fiber paper (CP), followed by sequential sulfurization and phosphidation. This catalyst achieves stable hydrogen and oxygen production in natural seawater, displaying outstanding oxygen evolution activity with an overpotential of just 390 mV at 10 mA/cm2 (Tafel slope: 426.5 mV/dec) and impressive hydrogen evolution activity with an overpotential of only 578 mV at 10 mA/cm2 (Tafel slope: 287.7 mV/dec). The two-electrode electrolyzer assembled by ZIF-9/CP-S-P || ZIF-9/CP-S-P was conducted the chronoamperometry test for 20000 s in 1 M phosphate buffer solution and for 100000 s in natural seawater, and its performance was comparable to that of commercial Pt/C || IrO2. These findings indicate the potential of ZIF-9/CP-S-P catalyst for practical applications in direct seawater splitting to produce hydrogen and oxygen.