Zn Dopants Synergistic Oxygen Vacancy Boosts Ultrathin CoO Layer for CO₂ Photoreduction

Abstract

Photoreduction of CO 2 without photosensitizers and scavengers runs into the development bottleneck for lack of excellent photocatalysts and ambiguous reduction mechanism. Herein, an ultrathin CoO layer containing Zn-dopants and O-vacancies (V o -Zn-CoO) is designed as an archetype to explore the influence mechanism of Zn on O-vacancies in ultrathin nanolayer for CO 2 photoreduction. DFT calculations illustrate that Zn-dopants not only reduce formation barriers of *COOH and *CO intermediates, but also form π-backbonding with *CO stimulating CH 4 evolution. Finally, V o -Zn-CoO layer significantly enhances CO 2 photoreduction efficiency and CH 4 selectivity with 26.8 µmol g −1 h −1 (63.8%) compared to 7.2 µmol g −1 h −1 (23.6%) for CoO layer with O-vacancies. Moreover, the synergistic effect of Zn and O-vacancies benefits the stability of O-vacancies in photocatalysts, achieving durable photocatalytic performance of V o -Zn-CoO layer. This work manifests that the strategy of metal atoms synergistic O-vacancies is effective to optimize CO 2 photocatalytic efficiency, selectivity, and stability of photocatalyst with O-vacancies.

Ni–Co Bimetallic Hydroxide Nanosheet Arrays Anchored on Graphene for Adsorption‐Induced Enhanced Photocatalytic CO2 Reduction

“…The selected area electron diffraction pattern (Figure 2f) for the Ni 7 Co 3 –GR composite showed distinct diffraction rings, indicating a polycrystalline structure. [ 20–23 ]…”

“…As shown in Figure 2a-c The selected area electron diffraction pattern (Figure 2f) for the Ni 7 Co 3 -GR composite showed distinct diffraction rings, indicating a polycrystalline structure. [20][21][22][23] We characterized the crystal structure of the synthesized samples using XRD. width at half maximum was found to be larger for GR than for GO.…”

Emerging Strategies for CO2 Photoreduction to CH4: From Experimental to Data‐Driven Design

“…The above two steps have widely been considered as rate‐determining steps for CH 4 production. [ 85,89,93,191 ] Both steps involve the formation of OH bonds. Next, the intermediate used to determine whether CO* is reduced to COH* or CHO* by forming OH or CH bonds, or forming CO gas, is the first major bifurcation.…”

“…In a recent study, the introduction of a Zn dopant to ultrathin O‐vacancy‐rich (V o )‐CoO layers increased the CH 4 yield by order of magnitude from 1.7 to 17.1 µmol g −1 h −1 , albeit accompanied by a modest increase in CO yield from 5.5 to 9.7 µmol g −1 h −1 (Figure 4b,c). [ 89 ] DFT calculations suggest that the Zn dopant not only reduces the energy barrier during the formation of the intermediates *COOH and *CO, but also improves the CO 2 photoreduction efficiency of the ultrathin V o ‐Zn‐CoO layer (Figure 4d); besides, similar to N doping, [ 60 ] the introduction of Zn increases the strength of CO adsorption on Vo‐Zn‐CoO, which is favorable for the reduction of *CO to CH 4 , whereas *CO on undoped Vo‐CoO tends to be released as CO. The 2π* orbital on V o ‐Zn‐CoO electron transfer to *CO stimulates the conversion of *CO to CH 4 while maintaining the stability of OVs on the V o ‐Zn‐CoO layer for its sustainable photocatalytic CO 2 reduction.…”

“…[211] The third step of photocatalytic CO 2 reduction reaction is surface reactions. Structural information of photocatalytic solid surfaces such as doping, [212] defect disorders, [89] and morphologies of solid surface, [213] also affect this process, which can be studied through the DFT calculation as well. Reproduced with permission.…”