Sub-nanometer Co₃O₄ clusters anchored on TiO₂(B) nano-sheets: Pt replaceable Co-catalysts for H₂ evolution

Abstract

Cobalt-based heterogeneous cocatalysts are important substitutions of noble metal cocatalysts in many important commercial chemical processes, but their efficiency is extremely low on a per metal atom basis, because only the atoms located at surface active-sites participate in the chemical reaction. Thus, cocatalysts with small cluster dispersions are highly desirable to maximize the amount of active-sites and enhance the per atom efficiency. Here, we report the synthesis of sub-nanometer CoO clusters which are anchored to 2D ultrathin TiO(B) nanosheets, as a cocatalyst for H evolution reaction (HER). It was found that the conduction type of CoO clusters turns from P-type to N-type, and the heterojunction band structure between TiO(B) and CoO clusters changes from type II to type I, when the cluster size is reduced from nanometer scale to the sub-nanometer scale. With a suitable energy band matching between TiO(B) and sub-nanometer CoO clusters, the electrons generated in TiO(B) during the photocatalytic process reduce the Co ions into metallic Co atoms, which produce excellent photocatalytic stability and extremely high HER efficiency comparable to that of the noble Pt cocatalyst.

Immobilization of Co, Mn, Ni and Fe oxide co-catalysts on TiO2 for photocatalytic water splitting reactions

“…The rest of the composites showed no activity indicating incapability of the generated MnO x , FeO x and CoO x species to act as co-catalysts for H + reduction, which is in stark contradiction to some of the literature reports. 34,41 We have further investigated the active NiO x -TiO 2 system in long run HER experiments to identify the maximum activity and investigate the performance stability. Fig.…”

“…Wet impregnation routes, on the other hand, are simple and costeffective: for example, by using metal salt impregnation followed by thermal decomposition. [26][27][28][29] Although some previous works have reported the synthesis and application of such cocatalyst-loaded TiO 2 powders in photocatalysis, 11,14,17,[30][31][32][33][34][35][36][37] many inconsistencies, originating from the wide variety of synthetic and calcination conditions, remain. Furthermore, the lack of comparative activity evaluations leave a gap in the fundamental understanding of their actual active state.…”

ZIF ‐67 derived hollow double‐shell core Co 3 O 4 modified g‐C 3 N 4 to construct p‐n heterojunction for efficient photocatalytic hydrogen evolution

“…For Co 3 O 4 , four distinct binding energy speaks can be split at 799.94, 780.71, 789.65, 795.00, 795.96, and 804.95 eV. Among them, the peaks at 799.94 and 780.71 eV are from Co 3+ and Co 2+ , respectively, the peaks at 795.00 and 795.96 eV are from Co 2p 1/2 , and the peaks at 789.65 and 804.95 eV are the satellite peaks of Co 37,42 . The spectrum of element C is shown in Figure 3E.…”

“…For Co 3 O 4 , four distinct binding energy speaks can be split at 799.94, 780.71, 789.65, 795.00, 795.96, and 804.95 eV. Among them, the peaks at 799.94 and 780.71 eV are from Co 3+ and Co 2+ , respectively, the peaks at 795.00 and 795.96 eV are from Co 2p 1/2 , and the peaks at 789.65 and 804.95 eV are the satellite peaks of Co. 37,42 The spectrum of element C is shown in Figure 3E. Obviously, in addition to the calibration peak at 284.8, g-C 3 N 4 has a binding energy peak at 288.12 eV that belongs to the sp 2 hybrid structure of CN C═N and the sp 2 hybrid structure of C NH 2 on the triazine ring.…”

Pd Clusters on Schiff Base–Imidazole-Functionalized MOFs for Highly Efficient Catalytic Suzuki Coupling Reactions

“…The catalytic activity of SNMCs will be further improved as the size decreases, due to the surface atomic structure, electronic structure, and defects will change significantly. However, because of high surface energy, a too tiny size could lead to aggregation and particle growth ( Tang et al, 2017 ; Si et al, 2018 ; Xin et al, 2018 ). A solution to the critical issue is to apply a nanoporous supporting material, such as graphene ( Gu et al, 2017 ; Liu et al, 2019 ), carbon nanofibers ( Eid et al, 2019 ), C 3 N 4 ( Yang et al, 2021 ; Zhang et al, 2021 ), and porous SiO 2 ( Peng et al, 2019 ).…”