Using density functional theory+U (DFT+U) calculations, we explore the effect of dopants on the performance of α-Fe₂O₃(0001) as an anode material for the oxygen evolution reaction (OER). Systematic screening of 3d, 4d, and 5d transition metal dopants indicates general trends with dopant band filling and allows us to identify the most efficient dopants with respect to the overpotential and relate those to the solution energy and electronic properties. Different conditions (electrochemical vs photoelectrochemical) are accounted for by considering hydroxylated, hydrated, and oxygenated terminations. Based on the DFT+U results, we identify Rh as the most promising dopant that can reduce the overpotential both under dark and illumination conditions: from 0.56 V to 0.48 V for the hydroxylated surface and quite substantially from 1.12 V to 0.31 V for the hydrated termination and from 0.81 V to 0.56 V for the oxygenated surface. The origin of this improvement is attributed to the modification of the binding energy of chemisorbed species to the Fe₂O₃(0001) surface. Investigation of the spin density of intermediate steps during the OER shows that surface iron ions adopt a wide range of oxidation states (+2, +3, and +4) in pure hematite, depending on the termination and chemisorbed species on the surface, but a Fe⁺³ state is stabilized predominantly upon doping. While Rh is in the +3 state in the bulk, it transforms to +4 at the surface and acquires a finite magnetic moment in several intermediate steps.

中文翻译：

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3d，4d和5ddopant对在黑暗和光照条件下α-Fe2O3（0001）处氧气释放反应的影响

使用密度泛函理论+ U（DFT + U）计算，我们研究了掺杂剂对α -Fe ₂ O ₃（0001）作为氧释放反应（OER）阳极材料的性能的影响。对3 d，4 d和5 d过渡金属掺杂剂的系统筛选表明了掺杂剂带填充的总体趋势，并使我们能够识别关于过电势的最有效的掺杂剂，并将其与溶液的能量和电子性质相关联。通过考虑羟基化，水合和氧化末端来考虑不同的条件（电化学与光电化学）。基于DFT + U结果，我们确定Rh是最有希望的掺杂剂，它可以在黑暗和光照条件下降低过电势：羟基化表面从0.56 V至0.48 V，水合端基从1.12 V至0.31 V，从0.81 V至0.41 V至氧化表面为0.56V。这种改进的起因归因于化学吸附物质与Fe ₂ O ₃（0001）表面结合能的改变。对OER期间中间步骤的自旋密度的研究表明，表面铁离子在纯赤铁矿中具有广泛的氧化态（+ 2，+ 3和+4），具体取决于表面上的终止基团和化学吸附物种，但是铁⁺³掺杂状态主要稳定状态。当Rh在整体中处于+3状态时，它在表面上转换为+4，并在几个中间步骤中获得了有限的磁矩。