Photogenerated Carriers Boost Water Splitting Activity over Transition-Metal/Semiconducting Metal Oxide Bifunctional Electrocatalysts

The development of a facile and general strategy to simultaneously enhance the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) activities of bifunctional electrocatalysts is of great importance for practical applications. However, current strategies are usually restricted to monofunctional electrocatalysts owing to the opposite redox process at cathode and anode. Herein, we present a photogenerated-carrier-driven strategy to enhance the electrocatalytic HER and OER activities of transition-metal/semiconductor bifunctional electrocatalysts. The Ni/NiO heterostructured ultrathin nanosheet array supported on Ni foam (denoted as Ni/NiO-NF) is chosen as the model metal/semiconductor bifunctional electrocatalyst and exhibits 10- and 2.6-fold enhancement of mass activity for HER and OER, respectively, after exposure to light irradiation. The increase in water-splitting activities can be attributed to the transfer of photogenerated electrons from excited NiO to HER-active Ni and the accelerating formation of OER-active NiIII/IV, respectively.