Synergetic Subnano Ni‐ and Mn‐Oxo Clusters Anchored by Chitosan Oligomers on 2D g‐C₃N₄ Boost Photocatalytic CO₂ Reduction

Abstract

Synergistic modulation of photogenerated electrons and holes of g‐C3N4 especially achieved by simply modifying bimetallic species is highly desired for efficient photocatalytic CO2 reduction. Herein, ultrasmall subnano Ni‐ and Mn‐oxo clusters (average diameter of ≈0.8 nm) are uniformly anchored on tailored chitosan oligomer (COS)‐functionalized ultrathin g‐C3N4 nanosheets via OH and NH2 in COS as the coordination sites. Optimized Ni and Mn comodified photocatalyst obtained by regulating bimetallic molar ratio exceptionally exhibits 22‐times CO2 conversion rate under solar‐light irradiation and ≈20‐times quantum efficiency at 405 nm light compared with pristine g‐C3N4. By electron paramagnetic resonance, surface photovoltage spectroscopy, fluorescence spectra, photoluminescence spectra, and electrochemical curves, it is evidenced the enhanced photoactivities originate from the synergetic effect between Ni‐ and Mn‐oxo species, capable of photoelectron‐capture along with catalytic CO2 activation and hole‐capture along with catalytic H2O activation, respectively. More importantly, due to the carrier‐modulating capability difference, it is verified only a matching Ni:Mn molar ratio leads to the best charge separation then photoactivity as supported by the transient‐state photoluminescence spectra. A new avenue to rationally modulate photogenerated charge carriers for fabricating efficient g‐C3N4‐based photocatalysts for solar‐fuel production is proposed.

Amide-functionalized covalent triazine framework for enhanced photocatalytic hydrogen evolution

“…In the transient state surface photovoltage (TS-SPV) spectra (Fig. 5c), the two positive signals (S1 and S2) of CTF-amide-16 indicate that photogenerated electrons migrated to the surface of CTF-amide-16 under the built-in electric field [62,63], consistent with the electrochemical results. Typically, the quick response signal (S1) indicates charge separation by drift under the built-in electric field, and the slow response signal (S2) suggests charge separation and transportation by diffusion [64].…”

Improving CO2 photoconversion with ionic liquid and Co single atoms

“…This suggests that Co single atoms trap holes instead of electrons to facilitate the charge separation (Supplementary Fig. 12c) 33 .…”

Strong ferromagnetism of g-C3N4 achieved by atomic manipulation

“…To fabricate the borate-functionalized 2D amorphous g-C 3 N 4 nanosheets (B-C 3 N 4 -X MPa), wherein B refers to the introduced boron bridges and X refers to the pressure of SC CO 2 , one-step SC CO 2 treatment was utilized, where H 3 BO 3 is used as the boron source. In this process, the straining and anisotropic acidic etching effect of SC CO 2 is expected to cleave the weak van der Waals forces between layers and the in-planar hydrogen bonds of tri-s-triazine units in the layers, thereby exfoliating bulk C 3 N 4 into 2D nanosheets, facilitating the formation of the amorphous and defective structure with -NH x groups [26][27][28][29][30] . Meanwhile, since H 3 BO 3 is presented over the preparation process, the empty sp 2 orbital on B of H 3 BO 3 is expected to be nucleophilic attacked by the lone pair of -NH x groups of the defected g-C 3 N 4 26 , forming in-planar bridging -B(OH)-groups (Fig.…”