Boosting the mass activity of perovskite electrocatalysts

Currently, noble metal-based electrocatalysts serve as the gold standard for the oxygen evolution reaction in various sustainable electrochemical energy technologies, including water electrolysis, rechargeable metal-air batteries, and regenerative fuel cells. However, their superior catalytic activity is partially offset by the materials’ high cost and scarcity.

Perovskite oxides have high intrinsic activity for the oxygen evolution reaction -- in some cases, even higher than noble metal-based catalysts -- but their low surface area results in unsatisfactory mass activity. To remedy this issue, She et al. investigated a molecular-level strategy to boost the mass transport behavior of perovskite electrocatalysts. They demonstrated an impressive fourfold mass activity enhancement in the optimized catalyst compared to pristine SrCo_0.8Fe_0.2O_3-δ (SCF) in a proof-of-concept study.

The commonly adopted strategy to promote mass transport in perovskites is to create porous structures at the macro scale, but preparation methods and fabrication processes are complex, expensive, and difficult to scale. Instead, the researchers employed a combination of crystal-structure engineering and sulfur doping to modulate the materials’ ordered oxygen vacancies and electronic structure.

Experimental and theoretical investigation of the optimized Sr₂Co_1.6Fe_0.4O_4.8S_0.2 (S-BM-SCF) catalyst determined that the intrinsic molecular-level pores on the structure can facilitate reactive hydroxyl ion (OH⁻) uptake into the oxygen vacant sites. In addition, sulfur doping further promotes OH⁻ adsorption by electronic structure modulation, thus accelerating the mass transport rate.

Overall, the researchers observed an increase in the catalytically active sites and improved mass transport of oxygen evolution reaction electrocatalysis, which led to significant mass activity enhancement compared to pristine SCF. In terms of future work, the researchers plan to focus on designing more advanced, non-noble electrocatalysts to reduce the cost of sustainable electrochemical energy technologies.

Source: “A molecular-level strategy to boost the mass transport of perovskite electrocatalyst for enhanced oxygen evolution,” by Sixuan She, Yinlong Zhu, Hassan A. Tahini, Zhiwei Hu, Shih-Chang Weng, Xinhao Wu, Yubo Chen, Daqin Guan, Yufei Song, Jie Dai, Sean C. Smith, Huanting Wang, Wei Zhou, and Zongping Shao, Applied Physics Reviews (2021). The article can be accessed at http://doi.org/10.1063/5.0033912 .