(a)
(b)
(c)
(d)
Figure 5: Photocatalytic hydrogen production on Co3O4-DC and Co3O4-WA under simulated solar light at (a) water/sacrificial agent (1 : 1); (b) pure water; (c) photocatalytic hydrogen production on Co3O4-DC and Co3O4-WA under visible light at pure water; (d) proposed mechanism for photocatalytic hydrogen production for Co3O4-DC at pure water.