A hierarchical oxygen vacancy-rich WO3 with nanowire-array-on-nanosheet-array structure for highly efficient oxygen evolution reaction

The search for highly efficient non-noble metal-based catalysts for the oxygen evolution reaction (OER) has received growing attention. Herein, we demonstrate a hierarchical oxygen vacancy-rich WO3 with nanowire array on nanosheet array (WO3 NWA-NSA) structure as a highly efficient catalyst for the OER. The vertical structure can not only highly improve the mass loading of WO3 catalysts on Ni foam, but also provide efficient paths and channels for electron and mass transfer, leading to superior catalytic activity. Besides, the oxygen vacancies in WO3 further promote the OER activity. The as-prepared WO3 NWA-NSA catalyst requires an extremely low overpotential of 0.23 V to achieve a benchmark of 10 mA cm(-2), with a Tafel slope of only 33 mV dec(-1), superior to most reported state-of-the-art nonprecious metal-based catalysts and noble oxide catalysts. Further theoretical modeling calculations indicate that the electronic structure of WO3 with oxygen vacancies fits extremely well with the requirements of OER catalysts. This facile strategy provides a new avenue toward the hierarchical design of electrocatalysts, and our research opens a brand-new field for the applications of WO3.