Modulation of Electronics of Oxide Perovskites by Sulfur Doping for Electrocatalysis in Rechargeable Zn–Air Batteries

Abstract

Oxygen electrocatalytic activities in oxide perovskites are strongly dependent on their conductivity and electron configurations (eg). Herein, we show that an appropriate level of sulfur doping in oxide perovskites (such as LaCoO3, LaNiO3, and LaFeO3) can not only enhance the conductivity but also transform the spin state of Co (Ni, Fe) from low to intermediate spin and, therefore, give rise to much accelerated oxygen electrocatalytic activities. Sulfur-doped LaCoO3 (S-LCO) exhibits significantly enhanced electrocatalytic activities in both oxygen evolution reactions and oxygen reduction reactions, as confirmed by first principle calculations and experimental observation, where the potential rate-determining step is accelerated owing to the introduction of S-dopants and oxygen defects. At the optimized S-doping level, S5.84%-LCO endows a rechargeable Zn–air battery with a high power density (92 mW/cm2 at 144 mA/cm2), excellent stability of charge/recharge, and a large open-circuit voltage of 1.47 V. This study shows that the engineering of the electronic state of oxide perovskite by S-doping is an effective pathway leading to high-performing bifunctional catalysis for energy storage and conversion.

High efficiency electrocatalyst of LaCr0.5Fe0.5O3 nanoparticles on oxygen-evolution reaction

“…The oxidation state and composition of the electracatalysts were detected via X-ray photoelectron spectroscopy (XPS). Figure 3 a exhibits La 3d spectra of LaFeO 3 , LaCr 0.5 Fe 0.5 O 3 and LaCrO 3 , which are deconvoluted into two different characteristic peaks of La 3d 3/2 (850.4 and 854.7 eV) and La 3d 5/2 (833.5 and 837.5 eV) 22 . Noting that the peak positions of LaCr 0.5 Fe 0.5 O 3 have a slight shift to low energy compared with LaFeO 3 and LaCrO 3 , revealing that there are valence change or electron transfer in LaCr 0.5 Fe 0.5 O 3 .…”

Activation Strategies of Perovskite‐Type Structure for Applications in Oxygen‐Related Electrocatalysts

“…Recently, it is also noticed that nonmetal elements (e.g., S, P, B, F) could be incorporated into perovskites to enhance the electrocatalytic performance. [ 131–135 ] For example, Li et al. reported that phosphorus could be doped into the B‐site LaFeO 3– δ perovskite‐type oxides via chemical route to boost the electrocatalytic performance.…”

“…The ion substitution can noticeably regulate electrical configuration of B‐site metal ions and electronic conductivity of perovskite to increase the electrocatalytic activity. [ 185,193–196 ] For example, Bian et al. reported Mg doped B‐site LaNiO 3 perovskite nanofibers were used as efficient bifunctional catalysts for rechargeable ZABs, and which exhibited higher catalytic OER/ORR activity than that of pristine LaNiO 3 .…”

“…In addition, due to the high chemical stability and mixed valence of Ce 3+ and Ce 4+ in the oxides, Ce doping is considered as an effective strategy to improve the electrocatalysis OER/ORR activities by adjusting the oxygen density on the catalyst surface. [ 195–198 ] Qian et al. reported the highly enhanced OER/ORR performance in Ce‐doped LaCoO 3 electrocatalysts ( Figure ).…”

Perovskite Oxides for Cathodic Electrocatalysis of Energy‐Related Gases: From O2 to CO2 and N2

“…[79,80] Different from P atom, which can substitute the B-site atom in perovskite oxides, S atom can be introduced into perovskite oxides by substituting O atom. [81,82] Taking LaCoO 3 as an example, the introduction of S can distort the [BO 6 ] octahedron (Figure 5c), and consequently induce oxygen defects. Moreover, in the S-containing LaCoO 3 (LaCoO 3 -S), it was found that the spin state of the B-site Co 3+ changed to the optimize e g -filling (Figure 5c).…”