Hexagonal Perovskite Ba_0.9Sr_0.1Co_0.8Fe_0.1Ir_0.1O_3−δ as an Efficient Electrocatalyst towards the Oxygen Evolution Reaction

Abstract

Currently, the oxygen evolution reaction (OER) plays a key role in the industrial application of renewable electrochemical technologies. Thus, developing electrocatalysts with high performance and sufficient stability for the OER is urgently pursued. Although perovskite oxides have provided numerous degrees of freedom for enhancing the electrocatalytic activity due to their diversity and flexibility, their investigation for the OER is mostly limited to pseudocubic structures. In this study, a complex perovskite oxide, Ba0.9Sr0.1Co0.8Fe0.1Ir0.1O3−δ (BSCFI-91), with a six-layer hexagonal (6H) structure, is synthesized first, displaying higher OER activity. Based on parent Ba0.9Sr0.1Co0.8Fe0.2O3−δ (BSCF-91), BSCFI-91 is obtained by replacing iron (Fe) with low-level iridium (Ir) doping and produces a current density of 10 mA cm–2 at a low overpotential of 300 mV, a small Tafel slope of 61.2 mV dec–1, and good stability up to 10 h in a 1.0 M KOH electrolyte. The dramatically enhanced OER performance is achieved by optimizing cobalt (Co) valence and highly oxidative oxygen species based on the hexagonal structure. The Ir incorporation facilitated the oxygen (O) p band center approaching to the Fermi level, indicating that BSCFI-91 could be a candidate in the electrocatalyst application. Moreover, this study opens up a new way to design efficient perovskite oxides for OER catalysis in terms of hexagonal crystal structures and composition modulation strategy.

Sm0.5Sr0.5Co1−xNixO3−δ—A Novel Bifunctional Electrocatalyst for Oxygen Reduction/Evolution Reactions

“…As shown in Figure 5e, the electron-transfer number of SSCN82 was closest to 4. It indicates that SSCN82 can restore O 2 to OH − via the desired four-electron pathway [16,40]. Combining the OER and ORR test results, it is obvious that SSCN82 has the most excellent OER and ORR performance, which proved that the synergy of Co and Ni with the suitable molar ratio is beneficial for the bifunctional activities [20].…”

Phase Engineering of Atomically Thin Perovskite Oxide for Highly Active Oxygen Evolution

“…The crystal structure of perovskite oxides generates the most powerful effect on their electronic structure, which results in a Madelung potential for each unique crystallographic site, controlling the intrinsic catalytic activity. [3,10,16,18,19,23,[27][28][29] To understand the effect of the crystal structure of perovskite oxides on OER activity at the atomic and electronic level, we resorted to ab initio density functional theory (DFT) calculations of LaMnO 3 surfaces of orthogonal, tetragonal, and hexagonal phases (Figure 1b). The calculated partial density of states diagrams of the transition metal d-band center of the surface Mn in LaMnO 3 of different phases are shown in Figure 1c, positioning at −1.88 eV, −2.55 eV, −1.74 eV for o-LMONs, t-LMONs, and h-LMONs, respectively.…”

“…The crystal structure of perovskite oxides generates the most powerful effect on their electronic structure, which results in a Madelung potential for each unique crystallographic site, controlling the intrinsic catalytic activity. [ 3,10,16,18,19,23,27–29 ]…”

Regulating Intrinsic Electronic Structures of Transition-Metal-Based Catalysts and the Potential Applications for Electrocatalytic Water Splitting

“…The (001) face with Ru atoms possessing the highest coordination numbers and the lowest surface energies is the most stable morphologically, which could reduce the generation and dissolution of higher-state Ru species. These findings inspire us to regulate the exposed crystal plane surfaces, where the electrochemical reactions occur to boost the electrocatalytic performances of TM-based nanocatalysts. − For instance, Ma and his co-workers synthesized surface-tailored Co 3 O 4 supported on Nitrogen doped reduced Graphene Oxide (N-rGO) to regulate the active sites of Co 3 O 4 spinel for OER . As shown in Figure a, three Co 3 O 4 nanocrystals with different shapes and terminal faces anchored on N-rGO were prepared through a hydrothermal method.…”