Abstract
Facile and reliable screening of cost-effective, high-performance and scalable electrocatalysts is key for energy conversion technologies such as water splitting. ABO3-δ perovskites, with rich constitutions and structures, have never been designed via activity descriptors for critical hydrogen evolution reaction (HER). Here, we apply coordination rationales to introduce A-site ionic electronegativity (AIE) as an efficient unifying descriptor to predict the HER activities of 13 cobalt-based perovskites. Compared with A-site structural or thermodynamic parameter, AIE endows the HER activity with the best volcano trend. (Gd0.5La0.5)BaCo2O5.5+δ predicted from an AIE value of ~2.33 exceeds the state-of-the-art Pt/C catalyst in electrode activity and stability. X-ray absorption and computational studies reveal that the peak HER activities at a moderate AIE value of ~2.33 can be associated with the optimal electronic states of active B-sites via inductive effect in perovskite structure (~200 nm depth), including Co valence, Co-O bond covalency, band gap and O 2p-band position.
Highlights
Facile and reliable screening of cost-effective, high-performance and scalable electrocatalysts is key for energy conversion technologies such as water splitting
By comparing single structural or thermodynamic parameter, we show that A-site ionic electronegativity (AIE), as a unifying electronic descriptor, has the most predictive power to identify a highly hydrogen evolution reaction (HER)-efficient oxide from more than 10 different cobalt-based perovskites via an optimal volcano-type activity trend. (Gd0.5La0.5)BaCo2O5.5+δ (Gd0.5)[10] predicted from an AIE value of ~2.33 shows a robust HER activity with an extremely high turnover frequency (TOF) value of ~22.9 s−1 at overpotential (η) of 0.24 V and a very small Tafel slope of 27.6 mV dec−1, which is the top-level catalytic performance among all metal oxides ever reported and even outperforms the most active noble metal Pt/C catalyst
We find that the thermodynamic parameter A–O bond energy cannot be rationally correlated with the intrinsic HER activity as no evident activity trends are observed (Supplementary Fig. 3); and the structure factor A-site ionic radius is not applicable to guide the activity of Sr-doped perovskites and the other perovskites roughly represent an imperfect volcano shape (Fig. 2b, d and Supplementary Fig. 4b)
Summary
Facile and reliable screening of cost-effective, high-performance and scalable electrocatalysts is key for energy conversion technologies such as water splitting. Eg occupancy[6], B-site oxidation state[23], outer electrons[24], multiphysicochemical material properties[25], and electrochemical redox potentials[26] were proposed to elucidate the OER/ORR catalytic activities. Despite these successful efforts, key limitations that plague the screening efficiency still remain: time-consuming and high-cost modeling and calculations for band structures or reaction processes are always involved in computational descriptors; and complex high-resolution characterizations such as synchrotron X-ray analytical techniques are indispensable for achieving accurate experimental properties of B-sites in synthesized perovskites for experimental descriptors. A-site cations can input their effects on the catalytic activity of perovskites in an indirect way by influencing the electronic and chemical states of B-site ions in perovskite lattice
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