Spatially separating redox centers on 2D carbon nitride with cobalt single atom for photocatalytic H ₂ O ₂ production

Abstract

Redox cocatalysts play crucial roles in photosynthetic reactions, yet simultaneous loading of oxidative and reductive cocatalysts often leads to enhanced charge recombination that is detrimental to photosynthesis. This study introduces an approach to simultaneously load two redox cocatalysts, atomically dispersed cobalt for improving oxidation activity and anthraquinone for improving reduction selectivity, onto graphitic carbon nitride (C3N4) nanosheets for photocatalytic H2O2production. Spatial separation of oxidative and reductive cocatalysts was achieved on a two-dimensional (2D) photocatalyst, by coordinating cobalt single atom above the void center of C3N4and anchoring anthraquinone at the edges of C3N4nanosheets. Such spatial separation, experimentally confirmed and computationally simulated, was found to be critical for enhancing surface charge separation and achieving efficient H2O2production. This center/edge strategy for spatial separation of cocatalysts may be applied on other 2D photocatalysts that are increasingly studied in photosynthetic reactions.

Synthesis of Leaf‐Vein‐Like g‐C3N4 with Tunable Band Structures and Charge Transfer Properties for Selective Photocatalytic H2O2 Evolution

“…[ 18a ] As for N 1s spectra, there are three component peaks at 398.5, 400.3, and 401.1 eV for pristine CN corresponding to bi‐coordinated N (CNC), tri‐coordinated N (N3C), and NH x groups in the heptazine framework, respectively. [ 17 ] The relative intensity of N–3C peak enhanced with increasing KBH 4 usage during the thermal polymerization, indicating the change of the relative content of nitrogen atoms in N3C and CNC. The corresponding atomic ratios of nitrogen in N3C and CNC were obtained by fitting the N 1s spectra and illustrated in Figure S4 (Supporting Information).…”

Single-Atom Photocatalysts for Emerging Reactions

“…Recently, two-dimensional (2D) carbon nitride (C 3 N 4 ) loaded with single-atom cobalt (Co) and anthraquinone (AQ) was synthesized for solar-light-driven H 2 O 2 generation. 38 Specifically, bulk C 3 N 4 was first exfoliated into C 3 N 4 nanosheets by ultrasonication. Then, single-atom Co was anchored onto the C 3 N 4 surface through Co ion coordination and pyrolysis in the N 2 atmosphere followed by phosphorylation.…”

“…For instance, several studies demonstrate the production of hydrogen peroxide (H 2 O 2 ) as a value-added chemical and potential energy carrier, using only water (H 2 O) and oxygen (O 2 ) via photocatalytic reduction reaction. 38 − 40 Moreover, phenol, as a key organic chemical intermediate and precursor, can be achieved via photocatalytic selective oxidation of benzene. 41 In another study, low-cost biomass-derived acetone is subject to oxidative C–C coupling to form 2,5-hexanedione (HDN) as an important chemical and redox agent to generate H 2 fuel through a photocatalytic redox reaction.…”

From photosynthesis to photocatalysis: Dual catalytic oxidation/reduction in one system

“…In summary, Chu et al in their study (22) simultaneously tackle the following challenges in photocatalysis in a platform of Co 1 / AQ/C 3 N 4 : 1) moving hole and electron away from where they are generated via exciton splitting upon light absorption to minimize the loss due to geminate recombination via a semiconductor 2D C 3 N 4 nanosheet; 2) segregating the photocatalytic oxidation cobalt site in the middle and reduction AQ site at the edge so that the two reactions can simultaneously take place without the needs for sacrificial donor/acceptor and external wiring; and 3) selecting proper AQ reduction site so that the reaction of forming H 2 O 2 is competitive with other reactions in both energetic and kinetic standpoints.…”

“…The work presented by Chu et al (22) titled "Spatially separating redox centers on 2D carbon nitride with cobalt single atom for photocatalytic H 2 O 2 production" has shown commendable progress to prolong photoinduced hole/electron separation time and distance in a synthetic platform using C 3 N 4 nanosheets that function as light-harvesting antenna and charge transport conduits. They cleverly designed twodimensional (2D) C 3 N 4 nanosheets to host a singleatom cobalt cocatalyst center at the voids in the middle of the sheet for the oxidative reactions and another cocatalyst anthraquinone (AQ) covalently linked at the edge of the nanosheets at least 1 nm away from the Co center for reductive reaction (Fig.…”