In-situ distortion of Bi lattice in Bi₂₈O₃₂(SO₄)₁₀ cluster boosted electrocatalytic CO₂ reduction to formate

To convert carbon dioxide into high-value-added liquid products such as formate with renewable electricity (CO₂RR) is a promising strategy of CO₂ resource utilization. The key is to find a highly efficient and selective electrocatalyst for CO₂RR. Herein, clustered Bi₂₈O₃₂(SO₄)₁₀ was found to show a high formate Faradaic efficiency (FE_formate) of 96.2% at –1.1 V_RHE and FE_formate above 90% in a wide potential range from –0.9 to –1.3 V_RHE in H-type cell, surpassing the corresponding layered Bi₂O₂SO₄ (85.6% FE_formate at –1.1 V_RHE). The advantageous CO₂RR performance of Bi₂₈O₃₂(SO₄)₁₀ over Bi₂O₂SO₄ was ascribed to a special two-step in-situ reconstruction process, consisting of Bi₂₈O₃₂(SO₄)₁₀ → Bi_–2.1/Bi₂O₂CO₃ → Bi_–2.1/Bi_–0.6 during CO₂RR. It gave metallic Bi_–2.1 with lattice distortion of –2.1% at the first step and metallic Bi_–0.6 with lattice distortion of –0.6% at the second step. In contrast, the usual layered Bi₂O₂SO₄ only formed metallic Bi_–0.6 with weaker lattice strain. The metallic Bi_–2.1 revealed higher efficiency in stabilizing *CO₂ intermediate and reducing the energy barrier of CO₂RR, while suppressing hydrogen evolution reaction and CO formation. This work delivers a high-performance cluster-type Bi₂₈O₃₂(SO₄)₁₀ electrocatalyst for CO₂RR, and elucidates the origin of superior performance of clustered Bi₂₈O₃₂(SO₄)₁₀ electrocatalysts compared with layered Bi₂O₂SO₄. © 2025 Dalian Institute of Chemical Physics, the Chinese Academy of Sciences