Synergy between Palladium Single Atoms and Nanoparticles via Hydrogen Spillover for Enhancing CO₂ Photoreduction to CH₄

Abstract

Selective photoreduction of carbon dioxide (CO2) into carbon‐neutral fuels such as methane (CH4) is extremely desirable but remains a challenge since sluggish multiple proton–electron coupling transfer and various C1 intermediates are involved. Herein, a synergistic function between single Pd atoms (Pd1) and Pd nanoparticles (PdNPs) on graphitic carbon nitride (C3N4) for photocatalytic CO2 methanation is presented. The catalyst achieves a high selectivity of 97.8% for CH4 production with a yield of 20.3 µmol gcat.−1 h−1 in pure water. Mechanistic studies revealed that Pd1 sites activated CO2, while PdNPs sites boosted water (H2O) dissociation for increased H* coverage. The H* produced by PdNPs migrate to the Pd1 sites to promote multiple proton–electron coupling transfer via hydrogen spillover. Moreover, the adjacent Pd1 and PdNPs effectively stabilized intermediates such as *CHO, thereby favoring the pathway for CH4 production. This work provides a new perspective into the development of selective photocatalytic CO2 conversion through the artful design of synergistic catalytic sites.

Phosphorus Tailors thed‐Band Center of Copper Atomic Sites for Efficient CO2Photoreduction under Visible‐Light Irradiation

“…As present in Figure 3e, the steady-state photoluminescence (PL) curve of Cu 1 N 3 @PCN displayed a relatively lower intensity than that of Cu 1 N 3 @CN and Cu 1 P 3 @PCN, indicative of a lower recombination rate of the electron-hole pairs under light irradiation, and hence a higher charge separation capability. [22] Such increased electron transfer for Cu 1 N 3 @PCN was further verified by the higher photocurrent density from the dynamic visible-light illumination responses and the smaller arc radius of Nyquist plot in the electrochemical impedance spectroscopy (EIS) (Figure S14 and S15). Moreover, according to the time-resolved photoluminescence (TRPL) decay spectra, Cu 1 N 3 @PCN showed the smallest average lifetime (τ a ) among three Cu catalysts, implying more efficient charge transfer from PCN to Cu 1 N 3 , thereby leading to a markedly suppressed charge recombination in Cu 1 N 3 @PCN (Figure S16 and Table S3).…”

Modulating Tit2gOrbital Occupancy in a Cu/TiO2Composite for Selective Photocatalytic CO2Reduction to CO

“…To confirm the reaction mechanism of CO 2 photoreduction, we performed an in situ Fourier-transform infrared spectroscopy (FTIR) test over Cu/TiO 2 -3 (Figure 4d) and pristine TiO 2 (Figure S14). The bands at 1612, 1314, and 1273 cm À 1 arose from the C=O stretch, CÀ O stretch, and OÀ H deformation of *COOH, respectively, which are regarded as vital intermediates during CO 2 reduction to CO. [47] The peak at 1436 cm À 1 can be attributed to the symmetric stretch of *HCO 3 . The area from 1800-2090 cm À 1 belongs to the vibration of the *CO intermediate.…”

Low‐Coordination Single Au Atoms on Ultrathin ZnIn2S4Nanosheets for Selective Photocatalytic CO2Reduction towards CH4

“…Despite much progress of SACs in CO 2 photoreduction process, the product distribution is still dominated by CO rather than CH 4 , [14] which is possibly limited by the carrier separation efficiency, the proton mobility rate, and adsorption strength of a single metal atom for CO 2 reduction intermediates. [15] Very recently, bimetallic sites catalysts, where the C and O atoms in CO 2 molecules are simultaneously bonded to two metal atoms to form a stable MÀ CÀ OÀ M model, have been reported to show high selectivity for photocatalytic reduction of CO 2 towards CH 4 . [8a, 16] However, great challenge still remains for photocatalytic CO 2 reduction to CH 4 with both high activity and high selectivity mediated via single metal sites.…”