Scalable Synthesis of Holey Deficient 2D Co/NiO Single‐Crystal Nanomeshes via Topological Transformation for Efficient Photocatalytic CO₂ Reduction

Abstract

Preparation of holey, single‐crystal, 2D nanomaterials containing in‐plane nanosized pores is very appealing for the environment and energy‐related applications. Herein, an in situ topological transformation is showcased of 2D layered double hydroxides (LDHs) allows scalable synthesis of holey, single‐crystal 2D transition metal oxides (TMOs) nanomesh of ultrathin thickness. As‐synthesized 2D Co/NiO‐2 nanomesh delivers superior photocatalytic CO2‐syngas conversion efficiency (i.e., VCO of 32460 µmol h−1 g−1 CO and VnormalH2${V_{{{\rm{H}}_2}}}$ of 17840 µmol h−1 g−1 H2), with VCO about 7.08 and 2.53 times that of NiO and 2D Co/NiO‐1 nanomesh containing larger pore size, respectively. As revealed in high‐angle annular dark‐field scanning transmission electron microscopy (HAADF‐STEM), the high performance of Co/NiO‐2 nanomesh primarily originates from the edge sites of nanopores, which carry more defect structures (e.g., atomic steps or vacancies) than basal plane for CO2 adsorption, and from its single‐crystal structure adept at charge transport. Theoretical calculation shows the topological transformation from 2D hydroxide to holey 2D oxide can be achieved, probably since the trace Co dopant induces a lattice distortion and thus a sharp decrease of the dehydration energy of hydroxide precursor. The findings can advance the design of intriguing holey 2D materials with well‐defined geometric and electronic properties.

Guest‐Induced Multilevel Charge Transport Strategy for Developing Metal‐Organic Frameworks to Boost Photocatalytic CO2 Reduction

“…[ 65 ] As shown in Figure S13, Supporting Information, the carbonate intermediates containing b‐CO 3 2− (≈1560, ≈1642, and ≈1297 cm −1 ), m‐CO 3 2− (≈1460 and ≈1250 cm −1 ), HCO 3 − (≈1442 and ≈1216 cm −1 ) and active CO 2 − (≈1602, ≈1548, and ≈1367 cm −1 ) were observed, demonstrating CO 2 adsorption and activation on the photocatalysts. [ 31 ] The peaks at ≈1500 and ≈1325 cm −1 can be assigned to *COOH (* is the adsorption state of the photocatalyst), which is the key intermediate during the CO 2 photoreduction process. [ 44 ] Based on the above experimental results, we further investigated the energetics of CO 2 reduction and simulated the possible catalytic course using DFT calculations, the intermediates of photocatalytic CO 2 reduction on BPAN ‐Co‐ 1 and BPAN ‐Co‐ 2 toward the production of CO were shown in Figure S14, Supporting Information.…”

Spatial Heterogeneity and Strong Coupling of FeII/FeIII in an Individual Metal‐Organic Framework Nanoparticle for Efficient CO2 Photoreduction

“…A larger amount of CO 2 desorption indicates stronger CO 2 binding affinity (chemical interaction) of the catalyst surface, and chemisorption has been well demonstrated to promote the capture and fixation of CO 2 on the catalyst surface. [ 34 ]…”

“…A larger amount of CO 2 desorption indicates stronger CO 2 binding affinity (chemical interaction) of the catalyst surface, and chemisorption has been well demonstrated to promote the capture and fixation of CO 2 on the catalyst surface. [34] Additionally, to assess the contribution of the valence states of Fe in PBA to CO 2 adsorption, density functional theory (DFT) calculations were run by constructing two models of standard Fe II Ni PBA (Ni II -NC-Fe II ) and Fe III Ni PBA (Ni II -NC-Fe III ) according to the preceding HRTEM, FT-IR, and XPS analyses. According to the DFT calculations (Figure 3f), the adsorption energy of CO 2 (ΔE ad-CO2 ) is negative on both Fe II Ni PBA and Fe III Ni.…”