This research aims to study process and mechanism of water splitting by photoelectrochemistry. Water splitting to produce hydrogen was initiated by photocatalysis on semiconductor of photovoltaic cell to growth the sufficient voltage so can be used for water electrolysis system by using tandem PV-EC cell. Visualization of water splitting has been monitoring with high resolution CMOS camera, 13 MPixel of OPPO X9006. This visualization has been modeling for hydrogen gas formation mechanism at carbon electrode (graphite) surface. PV Cell use Cu2O/Al as electrode with 0.003711 m2 surface area. Among ten PV cell series arrangement (surface area = 0.03711 m2), produce voltage between 3.01 V (room lights) ~ 3.43 V(neon lights) (this voltage was exceed minimum voltage for water splitting with voltage 1,47V) and current 509.8 μA and 438.7 μA. The process of water splitting observed at initiation of formation H2 gas and H2 release at carbon surface. Rate of H2 gas formation in the first 10 minutes is 1.72 x 10-5 ml/min, and stable with rate 1.17 x 10-5mL/min after 1 hour and 50 minutes. H2 gas volume produced reach 0.00281 mL after 5 hours 45 minutes.