Construction of Six‐Oxygen‐Coordinated Single Ni Sites on g‐C₃N₄ with Boron‐Oxo Species for Photocatalytic Water‐Activation‐Induced CO₂ Reduction

Abstract

The configuration regulation of single‐atom photocatalysts (SAPCs) can significantly influence the interfacial charge transfer and subsequent catalytic process. The construction of conventional SAPCs for aqueous CO2 reduction is mainly devoted toward favorable activation and photoreduction of CO2, however, the role of water is frequently neglected. In this work, single Ni atoms are successfully anchored by boron‐oxo species on g‐C3N4 nanosheets through a facile ion‐exchange method. The dative interaction between the B atom and the sp2 N atom of g‐C3N4 guarantees the high dispersion of boron‐oxo species, where O atoms coordinate with single Ni (II) sites to obtain a unique six‐oxygen‐coordinated configuration. The optimized single‐atom Ni photocatalyst, rivaling Pt‐modified g‐C3N4 nanosheets, provides excellent CO2 reduction rate with CO and CH4 as products. Quasi‐in‐situ X‐ray photoelectron spectra, transient absorption spectra, isotopic labeling, and in situ Fourier transform infrared spectra reveal that as‐fabricated six‐oxygen‐coordinated single Ni (II) sites can effectively capture the photoelectrons of CN along the BO bridges and preferentially activate adsorbed water to produce H atoms to eventually induce a hydrogen‐assisted CO2 reduction. This work diversifies the synthetic strategies for single‐atom catalysts and provides insight on correlation between the single‐atom configuration and reaction pathway.

Emerging Ultrahigh‐Density Single‐Atom Catalysts for Versatile Heterogeneous Catalysis Applications: Redefinition, Recent Progress, and Challenges

“…[149] In recent years, SACs have large metal utilization rate and highly density active sites and show excellent performance in many important catalytic reactions, which also provide a favorable research basis for exploring new AFC materials for photocatalytic CO 2 reduction reaction (see Table 3). [52,57,[150][151][152][153][154][155] Recently, Ma et al [150] proposed a pyrolysis-induced vaporization strategy to fabricate ultrahigh-density Co 1 /g-C 3 N 4 SACs with a record metal loading of 24.6 wt%, which revealed remarkable activity and selectivity for photocatalytic CO 2 reduction to CH 3 OH in the absence of both sacrificial reagent and photosensitizer (see Figure 15A-C). The Co single atoms were prepared by the pyrolysis-induced vaporization process in a two-step calcination procedure.…”

Surface Modification of 2D Photocatalysts for Solar Energy Conversion

“…Wang et al have developed the H 3 BO 3 bonding strategy for constructing isolated-transition-metal-single-atoms (Ni, Co, Fe)-decorated g-C 3 N 4 nanosheets. [166] In this strategy, boron-oxo species are uniformly distributed on the surface of g-C 3 N 4 by BN coordination, which further acts as a bridge to stabilize the isolated transition-metal atoms (Figure 10A). The experimental results indicate that the isolated-Ni-atom-modified g-C 3 N 4 exhibits the highest product (CH 4 and CO) evolution rates comparing with nonprecious-metal-decorated singleatom catalysts.…”

“…Moreover, the presence of Co single atom is conducive to the adsorption and activation of CO A-E) Reproduced with permission. [166] Copyright 2021, Wiley-VCH. F) Atomic-resolution HAADF-STEM images of Co-Bi 3 O 4 Br.…”

“…D) Water adsorption energies for CN, 5OBCN, and 0.7Ni-5OB-CN, respectively. E) The possible hydrogen-assisted CO 2 reduction process mechanism over single-atom Ni-OB-CN photocatalyst under illumination.A-E) Reproduced with permission [166]. Copyright 2021, Wiley-VCH.…”

Novel Cerium‐Based Sulfide Nano‐Photocatalyst for Highly Efficient CO2Reduction

“…Recently, CO 2 photoreduction into highvalue chemicals has aroused widespread attention as a promising strategy to alleviate the energy shortage and air pollution problems. [1][2][3][4] Therefore, many efforts have been devoted to investigating effective photocatalysts for CO 2 reduction, for which several types of photocatalysts including metal oxides, [5][6][7] carbon nitrides, [8][9][10] and sulfides [11,12] have proved suitable. For example, Collado et al [13] designed an Ag/TiO 2 photocatalyst with surface sub-bandgap states that promoted the efficient separation of photogenerated charge carriers, and Xia et al [8] synthesized defective crystalline carbon nitride with extended optical absorption and improved charge-transfer ability, both photocatalysts showing enhanced CO 2 photoreduction performance.…”