A novel photocatalytic water splitting device was constructed using economic graphene quantum dots as a photocatalyst and a Ni-based complex [(tpy-CH![[double bond, length as m-dash]](http://www.rsc.org/images/entities/char_e001.gif)
N)2Ni]Cl2 (tpy = terpyridine) as a co-catalyst. Under visible light irradiation and with a bias of −0.1 V vs. NHE, it produced an extremely stable photocurrent density of −9 μA cm−2 for 3 h.
