Investigation of oxygen vacancies in Fe2O3/CoOx composite films for boosting electrocatalytic oxygen evolution performance stably

Abstract Oxygen-defective Fe 2 O 3 /CoO x nanorod array composite films are prepared using a facile and environmentally friendly photodeposition method followed by annealing in oxygen deficient atmosphere. Compared with the original Fe 2 O 3 /CoO x sample, the optimized oxygen-defective Fe 2 O 3 /CoO x composite film electrode annealed at 250 °C has a 120 mV negative shifting of overpotential and lower Tafel slope. Moreover, the optimized oxygen-defective Fe 2 O 3 /CoO x composite film electrode exhibits competitive OER stability for 16 h. This can be attributed to numerous active sites on oxygen-defective CoO x and its weak crystallinity that promises excellent activity as well as stability. Furthermore, the amount of oxygen vacancies in CoO x can be finely tuned by changing annealing temperature. Based on XPS spectra and electrochemical analysis results, we show the relationship between the electronic states of Co and its electrocatalytic OER activity. The results may find broad applications in designing highly efficient catalysts for electrochemical process.