Oxygen vacancy-engineered Fe2O3 porous microspheres with large specific surface area for hydrogen evolution reaction and lithium-sulfur battery

Iron oxide (Fe 2 O 3 ) with intrinsic catalytic activity and desirable theoretical capacity are expected to be promising active materials for hydrogen evolution reaction (HER) and lithium-sulfur (Li-S) batteries. Nevertheless, the sluggish electrons transfer accompanied with limited active sites impede their large-scale application. Generally, the silicon dioxide (SiO 2 ) is employed as sacrificial template to regulate morphological structure of target products. However, selecting SiO 2 as sacrificial shell may be a novel method to overcome the limitations and further optimize the performance of Fe 2 O 3 . Hence, a novel self-activation strategy along with reduction treatment is presented to prepare oxygen vacancy-engineered Fe 2 O 3 porous microspheres featured with high specific surface area (SA-Fe 2 O 3 (O v )). Specifically, the simultaneously formation of rich oxygen vacancies and porous configuration could regulate electronic configuration, expose numerous active sites and enhance electrons transfer, leading to superior achievement for HER and Li-S batteries. Remarkably, the elaborately designed SA-Fe 2 O 3 (O v ) achieves low overpotential and relatively small Tafel slopes. Furthermore, SA-Fe 2 O 3 (O v ) holds great promise serving as sulfur host in the field of Li-S batteries with reversible capacity and impressive durability. This work contributes new insights into the self-activation strategy coupled with reduction synthesis of oxygen vacancy-engineered porous oxides with large specific surface area and raises the understanding of multifunctional energy applications. Inverted design of oxygen vacancy-engineered Fe 2 O 3 porous microspheres featured with high specific surface area is proposed via a facile encapsulated self-activation strategy combined with partial reduction method. Usually, SiO 2 is always engaged as sacrificial core to construct target hollow/porous products. Whereas we propose the inverted design of SiO 2 as sacrificial shell to prepare SA-Fe 2 O 3 (O v ) microspheres featured with large specific surface area. This present strategy of using self-activation, oxygen-vacancy and phosphate ions to enhance electrochemical properties may open up new opportunities for developing high-performance metal oxide catalysts for energy storage and conversation. • Oxygen vacancy-engineered Fe 2 O 3 porous microspheres are proposed via self-activation strategy and partial reduction method. • We propose the inverted design of SiO 2 as sacrificial shell to prepare SA-Fe 2 O 3 (O v ) microspheres. • The rich oxygen vacancies within SA-Fe 2 O 3 (O v ) microspheres could offer superior conductivity and rich active sites. • The phosphate ions is favorable for weakening the activation energy of their redox reactions.