Epitaxially grown silicon-based single-atom catalyst for visible-light-driven syngas production

Abstract

Improving the dispersion of active sites simultaneous with the efficient harvest of photons is a key priority for photocatalysis. Crystalline silicon is abundant on Earth and has a suitable bandgap. However, silicon-based photocatalysts combined with metal elements has proved challenging due to silicon’s rigid crystal structure and high formation energy. Here we report a solid-state chemistry that produces crystalline silicon with well-dispersed Co atoms. Isolated Co sites in silicon are obtained through the in-situ formation of CoSi2 intermediate nanodomains that function as seeds, leading to the production of Co-incorporating silicon nanocrystals at the CoSi2/Si epitaxial interface. As a result, cobalt-on-silicon single-atom catalysts achieve an external quantum efficiency of 10% for CO2-to-syngas conversion, with CO and H2 yields of 4.7 mol g(Co)−1 and 4.4 mol g(Co)−1, respectively. Moreover, the H2/CO ratio is tunable between 0.8 and 2. This photocatalyst also achieves a corresponding turnover number of 2 × 104 for visible-light-driven CO2 reduction over 6 h, which is over ten times higher than previously reported single-atom photocatalysts.

Efficient Interfacial Sites between Metallic and Oxidized Cobalt for Propene Hydroformylation

“…To explore the electronic properties, we carried out X-ray photoelectron spectroscopy (XPS) characterizations of Co/N–C-600, Co/N–C-800, and Co/N–C-1000. As shown in Co 2p XPS spectra, the content of metallic Co 0 increased from Co/N–C-600 to Co/N–C-800 and Co/N–C-1000 − (Figure e). N 1s XPS spectra showed that the peaks at 399.4, 401.4, 400.2, and 398.8 eV were ascribed to Co–N, graphitic N, pyrrolic N, and pyridinic N, respectively , (Figure f).…”

A molecular view of single-atom catalysis toward carbon dioxide conversion

“…More recently, a silicon-based Co SAC was reported for the production of syngas with a highly tunable H/C ratio. 239 A solid-state epitaxy method was used for the construction of such a SAC with Co SAs well dispersed on crystalline silicon, through a multistep variable-temperature annealing including the preliminary incorporation of Co atoms in the Si lattice and the following decomposition of the CoSi 2 domain. With the addition of a particular photosensitizer and sacrificial agent, CO and H 2 yields of 4.7 mol g (Co) −1 and 4.4 mol g (Co) −1 were achieved through visible-light-driven CO 2 reduction, in which the H/C ratio could be tuned from 0.8 to 2 by modulating the Co loading amount.…”

Insight into the Selectivity-Determining Step of Various Photocatalytic CO2 Reduction Products by Inorganic Semiconductors

“…TON (Equation ), which represents the maximum achievable turnover number in unit time, is a crucial parameter for evaluating the practicality of a catalyst in industrial applications TON = Number of reacted electrons per second Number of active sites in a photocatalyst …”

“…In industrial applications, maintaining a stable CO/H 2 ratio is crucial as syngas with ratios of 1:1, 1:2, and 1:3 serves as raw materials for hydroformylation, methanol synthesis, and methanation reactions, respectively. , Therefore, achieving continuous syngas production at a consistent CO/H 2 ratio represents a key objective in developing photocatalytic syngas production units. Zhenyu Yang proposed that the in situ formation of metal silicide could facilitate silicon growth and enable the incorporation of dopant metals into the metal silicide/silicon interface. Consequently, cobalt silicide (CoSi 2 ) was employed as a template to promote the atomic epitaxy-based in situ growth of diamond-structured crystalline Si (c-Si), thereby incorporating Co atoms into the high-temperature domain of c-Si lattice during CoSi 2 decomposition.…”

“…The error is due to the deviation of multiple measurements. Reproduced with permission . Copyright 2023, Nature Communications.…”