Unveiling Catalytic Sites in a Typical Hydrogen Photogeneration System Consisting of Semiconductor Quantum Dots and 3d-Metal Ions

Abstract

Semiconductor quantum dots (QDs) in conjunction with non-noble 3d-metal ions (e.g., Fe 3+ , Co 2+ , and Ni 2+ ) have emerged as an extremely efficient, facile, and cost-effective means of solar-driven hydrogen (H 2 ) evolution. However, the exact structural change of the active sites under realistic conditions remains elusive, and the mechanism of H 2 evolution behind the remarkable activity is poorly understood. Here, we successfully track the structural variation of the catalytic sites in the typical H 2 photogeneration system consisting of CdSe/CdS QDs and 3d-metal ions (i.e., Ni 2+ used here). That is, the nickel precursor of Ni(OAc) 2 changes to Ni(H 2 O) 6 2+ in neutral H 2 O and eventually transforms to Ni(OH) 2 nanosheets in alkaline media. Furthermore, the in operando spectroscopic techniques of electron paramagnetic resonance and X-ray absorption spectroscopy reveal the photoinduced transformation of Ni(OH) 2 to a defective structure [Ni x 0 /Ni 1−x (OH) 2 ], which acts as the real catalytic species of H 2 photogeneration. Density functional theory (DFT) calculations further indicate that the surface Ni-vacancies (V Ni ) on the Ni(OH) 2 nanosheets enhance the adsorption and dissociation of H 2 O molecules to enhance the local proton concentration, while the Ni 0 clusters behave as H 2 -evolution sites, thereby synergistically promoting the activity of H 2 photogeneration in alkaline media.

Electrocatalytic upcycling of polyethylene terephthalate to commodity chemicals and H2 fuel

“…29a, b ), suggesting a possible catalyst activation process. This might be a result of catalyst surface reconstruction, which has been identified in many electrocatalysts (especially for OER) 39 , 47 , 48 and photocatalysts 49 , 50 . For better understanding of the reconstruction of the catalyst, a carbon cloth-supported CoNi 0.25 P catalyst was prepared (Supplementary Fig.…”

An All‐Organic D‐A System for Visible‐Light‐Driven Overall Water Splitting

“…Furthermore, Gibbs free energy change of H* adsorption (Δ G H *) is considered to be an important descriptor to evaluate the H 2 evolution performance, which is calculated by DFT calculations. [ 63–65 ] As shown in Figure 5f and Table S4 (Supporting Information), for Bulk CN and TCN, the calculated Δ G H * values are −0.41 and −0.45 eV. Dramatically, after grafting carbon rings units into the basal plane of TCN, the Δ G H * value of C‐TCN is reduced to −0.25 eV, which is very close to that of Pt (−0.09 eV), indicating that the H 2 evolution reaction activity of C‐TCN is greatly promoted.…”

Engineering one-dimensional hollow beta-In2S3/In2O3 hexagonal micro-tubes for efficient broadband-light photocatalytic performance

“…13,14 Semiconductors have been widely used as visible-light-active photocatalysts because of their outstanding optical properties, tunable structures and chemical stability. [15][16][17] Unfortunately, the low visiblelight absorption and the high recombination rate of photogenerated electron and hole pairs are two critical drawbacks that hinder the improvement of the photocatalytic activity of semiconductors nowadays. [18][19][20] Selecting a semiconductor with an appropriate bandgap for absorption of broadband-light plays an important role in enhancing the light utilization.…”