Strain Effect on Oxygen Evolution Reaction Activity of Epitaxial NdNiO₃ Thin Films

Abstract

Epitaxial strain can cause both lattice distortion and oxygen nonstoichiometry, effects that are strongly coupled at heterojunctions of complex nickelate oxides. Here we decouple these structural and chemical effects on the oxygen evolution reaction (OER) by using a set of coherently strained epitaxial NdNiO3 films. We show that within the regime where oxygen vacancies (VO) are negligible, compressive strain is favorable for the OER whereas tensile strain is unfavorable; the former induces orbital splitting, resulting in a higher occupancy in the d3z 2−r 2 orbital and weaker Ni–O chemisorption. However, when the tensile strain is sufficiently large to promote VO formation, an increase in the OER is also observed. The partial reduction of Ni3+ to Ni2+ due to VO makes the eg occupancy slightly larger than unity, which is thought to account for the increased OER activity. Our work highlights that epitaxial-strain-induced lattice distortion and VO generation can be individually or collectively exploited to tune OER activity, which is important for the predictive synthesis of high-performance electrocatalysts.

Trends of epitaxial perovskite oxide films catalyzing the oxygen evolution reaction in alkaline media

“…The aspect has been well studied [54,55,61,74] and the influence on the OER has been attributed to resulting changes in crystal field splitting due to octahedral distortion [61] and bond angles, i.e. hybridization [54,74]. Different approaches have been taken to assemble electrodes from epitaxial thin films for electrocatalytic investigations.…”

“…Thus, minimal strain is strongly recommended for LaNiO3 films. Yet, for NdNiO3 films, the activity increases with either compressive or tensile strain [54]. The authors argue that the former is beneficial for OER due to an enhanced p-d hybridization [133] and the latter due to the formation of oxygen vacancies and the concomitant reduction of Ni, which increases the average eg occupancy to slightly above unity, i.e.…”

“…Instead it illustrates the limits of the eg descriptor. Many of the reports included in our plot discussed qualitative deviations from the formal valence [53,54,68,[55][56][57][58][59]61,65,67], In that sense, the eg descriptor is not very robust against guessing it from the formula and it should be quantified consistently by measurement for films made by identical deposition methods. As a final remark, the spread of the data at eg occupancy of one (210 mV) as compared to the span of overpotentials in Fig.…”

“…The symbol shape indicates the substrate and the color the B-site metal. The data was taken from refs [28,53,[62][63][64][65][66][67][68][69][70][54][55][56][57][58][59][60][61]…”

Low‐Coordinate Iridium Oxide Confined on Graphitic Carbon Nitride for Highly Efficient Oxygen Evolution

“…Third, the superhydrophilic GCN nanosheets endow the heterostructured catalyst system as uperhydrophilic surface, which is critical for the electrolyte penetration and gas adsorption/desorption kinetics. [19] According to the static contact angle measurements (Figure 4c,d;S upporting Information, Videos S1-S3), [20] 40-IG becomes superhydrophilic with ac ontact angle of 08 8 after introducing the superhydrophilic GCN nanosheets (Supporting Information, Figure S8). Thes uperhydrophilicity of 40-IG would substantially facilitate OER kinetics.M oreover,aphysical mixed IrO 2 -GCN sample also exhibits improved hydrophilicity (Supporting Information, Figure S9) and enhanced catalytic activity than bare IrO 2 (Supporting Information, Figure S10), further verifying the significance of hydrophilicity for faster oxygen evolution.…”