Theoretical Insight on Anion Ordering, Strain, and Doping Engineering of the Oxygen Evolution Reaction in BaTaO₂N

Abstract

Oxynitride perovskites such as BaTaO 2 N are among the most promising materials to achieve efficient direct solar-to-chemical conversion. Albeit photoelectrochemical water splitting has been demonstrated, the required overpotentials remain prohibitively large compared with the theoretically accessible values, particularly for the oxygen evolution reaction (OER). Here, we apply density functional theory (DFT) calculations to investigate the use of strain and cationic doping with Ca and Sr to optimize the OER theoretical overpotential. For the TaON-terminated BaTaO 2 N (001) surface, 4% compressive uniaxial strain can lower the theoretical overpotential to η = 0.59 V, under operational conditions. For the most stable TaO 2 N-(100) termination, 1% tensile uniaxial strain, which is perfectly accessible by experiments, is enough to reduce the theoretical overpotential from η = 0.43 V to η = 0.37 V under (photo)electrochemical conditions. This value is close to the minimum predicted theoretical overpotential and points out how strain engineering could be efficiently used to improve the electrocatalytic reactions.

First-principles calculations of the structural, energetic, electronic, optical, and photocatalytic properties of BaTaO2N low-index surfaces

“…Our results suggest that for (001) and (100) surfaces, the termination exposed with Ta is more stable than that exposed with Ba in both trans and cis configurations. The same trend was found by Lan et al 24 Considering all the investigated terminations above, we found that t -(100)-TaO 2 has the lowest surface energy but the corresponding trans bulk has a higher energy than the cis bulk. This can be related to the fact that a less favorable bulk phase will have a smaller cleavage energy compared to a stable bulk phase.…”

“…Very recently, Lan et al explored the mechanism of the OER on the (001) and (100) surfaces of cis BaTaO 2 N. They found that the overpotentials were 0.97 V for c -(001)-TaON and 1.64 V for c -(100)-Ta 2 O 3 N, which are different from the results obtained in this work. 24 There are two possible reasons: they only considered one possible structure of the intermediate in every step of the OER, and they used slab models with even layers.…”

“…However, experimental findings revealed that the surface modification and the interface construction are very important for enhancing the photocatalytic performance of BaTaO 2 N. Therefore, it is necessary to understand the relationship between the surface structure and physicochemical properties of the semiconductor. Very recently, Lan et al studied the effect of strain, anion ordering and cationic doping modifications on the OER theoretical overpotential for the TaO 2 N-terminated (100) and TaON-terminated (001) surfaces of cis BaTaO 2 N. 24 Hojamberdiev et al applied molecular dynamics calculations to investigate the effect of cation doping on the adsorption energy of water molecules and formed intermediates on the BaTaO 2 N surfaces terminated with TaO 6 , TaN 6 , and TaO 4 N 2 octahedra. They found that the experimental photocatalytic reaction rates were well described by using the adsorption energies of the reaction intermediates.…”

Time-Retrenched Synthesis of BaTaO2N by Localizing an NH3 Delivery System for Visible-Light-Driven Photoelectrochemical Water Oxidation at Neutral pH: Solid-State Reaction or Flux Method?

“…Annealing of inactive as-synthesized BaTaO 2 N particles in Ar was found to be advantageous to maximize the photocurrent to 6.5 mA·cm –2 at 1.23 V vs RHE, which showed good stability over 24 h (79% initial photocurrent was retained) . Very recently, Castelli and co-workers found that the theoretical overpotential of the TaO 2 N-(100) surface of BaTaO 2 N can be effectively decreased to 0.37 V under (photo)­electrochemical conditions by applying 1% tensile uniaxial strain. Considering all of the above-mentioned advantages of BaTaO 2 N over other metal (oxy)­nitrides, further studies are however indispensable to further enhance the efficiency and stability of BaTaO 2 N for the design and manufacturing of photoelectrochemical tandem cells to meet the prerequisites for overall water splitting. − In any case, the electrochemical properties are responsible for these effects, and it is important to study the trends in the conditions that will resolve the optoelectronic effects to understand and guide improvements.…”

Electronic modulation of cobalt–molybdenum oxideviaTe doping embedded in a carbon matrix for superior overall water splitting

“…5c). 66 Remarkably, the electrolyzer of Te-CoMoO 3 @C can stably work for up to 100 h at 10 mA cm −2 , which greatly outperforms the commercial Pt/C||RuO 2 catalysts (Fig. 5d).…”