Electrodeposition of nickel cobaltite oxide semiconductor thin film: Photocathode fabrication

Nowadays, the matter of energy and fuel supplying via sustainable approaches, using renewable sources has gained a global importance. In this regard, the utilization of solar energy and fabrication of semiconducting photoelectrodes play a crucial role; using this strategy, sunlight is directly converted to electricity or the energy is stored as fuel (chemical bond) [1]. Herein, with applying an appropriate aqueous electrolyte containing Co (II) and Ni (II) nitrate, a green film of Layered Double Hydroxide (LDH) was cathodically electrodeposited on fluorine-doped tin oxide (FTO) glass and copper substrates, and the film was then converted to a black porous nickel cobaltite oxide (NiCo2O4; NCO) by annealing in the ambient atmosphere [2]: NO3 − + 7H2O + 8e− → NH4 + + 10 OH− (1) M2+ + 2OH− → M(OH)2 ; M = Ni, Co (2) Ni(OH)2 + 2Co(OH)2 + 1 2 O2 473 K → NiCo2O4 + 3H2O (3) Mott-Schottky analyses revealed a p-type conductivity for the fabricated electrodes (majority charge carriers: hole, flat-band potential: 0.9VSCE at pH=6.2). Furthermore, due to strong absorption in a broad spectral region (Eg = 2.1 eV; Tauc s plot), it was suggested that the Schottky junction NCO/Cu electrode fabricated here, could be employed as an affordable/potential photoelectrode for effective harnessing of photons and application in cathodic reactions [3].