Light-Reinforced Key Intermediate for Anticoking To Boost Highly Durable Methane Dry Reforming over Single Atom Ni Active Sites on CeO2.

Dry reforming of methane (DRM) has been investigated for more than a century; the paramount stumbling block in its industrial application is the inevitable sintering of catalysts and excessive carbon emissions at high temperatures. However, the low-temperature DRM process still suffered from poor reactivity and severe catalyst deactivation from coking. Herein, we proposed a concept that highly durable DRM could be achieved at low temperatures via fabricating the active site integration with light irradiation. The active sites with Ni-O coordination (NiSA/CeO2) and Ni-Ni coordination (NiNP/CeO2) on CeO2, respectively, were successfully constructed to obtain two targeted reaction paths that produced the key intermediate (CH3O*) for anticoking during DRM. In particular, the operando diffuse reflectance infrared Fourier transform spectroscopy coupling with steady-state isotopic transient kinetic analysis (operando DRIFTS-SSITKA) was utilized and successfully tracked the anticoking paths during the DRM process. It was found that the path from CH3* to CH3O* over NiSA/CeO2 was the key path for anticoking. Furthermore, the targeted reaction path from CH3* to CH3O* was reinforced by light irradiation during the DRM process. Hence, the NiSA/CeO2 catalyst exhibits excellent stability with negligible carbon deposition for 230 h under thermo-photo catalytic DRM at a low temperature of 472 °C, while NiNP/CeO2 shows apparent coke deposition behavior after 0.5 h in solely thermal-driven DRM. The findings are vital as they provide critical insights into the simultaneous achievement of low-temperature and anticoking DRM process through distinguishing and directionally regulating the key intermediate species.

Mechanistic insight into the active centers of single/dual-atom Ni/Fe-based oxygen electrocatalysts.

Single-atom catalysts with maximum metal utilization efficiency show great potential for sustainable catalytic applications and fundamental mechanistic studies. We here provide a convenient molecular tailoring strategy based on graphitic carbon nitride as support for the rational design of single-site and dual-site single-atom catalysts. Catalysts with single Fe sites exhibit impressive oxygen reduction reaction activity with a half-wave potential of 0.89 V vs. RHE. We find that the single Ni sites are favorable to promote the key structural reconstruction into bridging Ni-O-Fe bonds in dual-site NiFe SAC. Meanwhile, the newly formed Ni-O-Fe bonds create spin channels for electron transfer, resulting in a significant improvement of the oxygen evolution reaction activity with an overpotential of 270 mV at 10 mA cm-2. We further reveal that the water oxidation reaction follows a dual-site pathway through the deprotonation of *OH at both Ni and Fe sites, leading to the formation of bridging O2 atop the Ni-O-Fe sites.

The role of potassium in the activation of oxygen to promote nitric oxide oxidation on honeycomb-like h-BN(001) surfaces.

Two-dimensional materials have developed rapidly in the field of catalysis, which has made honeycomb-like 2D hexagonal boron nitride (h-BN) considered to be a promising material in the application of catalysis. In this study, potassium (K) modified h-BN(001) surfaces are designed for the first time for the purpose of removal of nitric oxide (NO) via dispersion corrected density functional theory (DFT) computations. The role of K in changing the electronic properties and processes of NO oxidation is investigated in detail. The introduction of K effectively narrows the band gap of h-BN and acts as the surface electron donor on the surface. Importantly, the energy barrier is decreased by 3.45 eV at most along the whole NO oxidation path on K-doped h-BN(001), which is directly ascribed to the spontaneous dissociation of O2 induced by K and efficient charge transfer across the interface. The activation of O2 may be beneficial to other analogous oxidation reactions. With the introduction of K, the energy barrier of NO2 conversion to NO3- is significantly decreased and the desorption of NO2 is inhibited. Hence, NO3- instead of NO2 becomes the main oxidation product on K-modified h-BN. This work may provide new insights into the role of alkali metals in the activation of O2 to facilitate oxidation reactions on 2D materials.

Efficient photocatalytic hydrogen evolution with ligand engineered all-inorganic InP and InP/ZnS colloidal quantum dots.

Photocatalytic hydrogen evolution is a promising technique for the direct conversion of solar energy into chemical fuels. Colloidal quantum dots with tunable band gap and versatile surface properties remain among the most prominent targets in photocatalysis despite their frequent toxicity, which is detrimental for environmentally friendly technological implementations. In the present work, all-inorganic sulfide-capped InP and InP/ZnS quantum dots are introduced as competitive and far less toxic alternatives for photocatalytic hydrogen evolution in aqueous solution, reaching turnover numbers up to 128,000 based on quantum dots with a maximum internal quantum yield of 31%. In addition to the favorable band gap of InP quantum dots, in-depth studies show that the high efficiency also arises from successful ligand engineering with sulfide ions. Due to their small size and outstanding hole capture properties, sulfide ions effectively extract holes from quantum dots for exciton separation and decrease the physical and electrical barriers for charge transfer.

CdSe Quantum Dots/g-C3N4 Heterostructure for Efficient H2 Production under Visible Light Irradiation.

Novel photocatalysts -CdSe quantum dots (QDs)/g-C3N4- were successfully constructed. The structure, chemical composition, and optical properties of the prepared samples were investigated via a series of characterization techniques. The results indicated that CdSe QDs/g-C3N4 photocatalysts exhibited remarkably enhanced photocatalytic activity for visible-light-induced H2 evolution compared to pristine g-C3N4 and CdSe QDs and addition of 13.6 wt % CdSe QDs into the composite photocatalyst generated the highest H2 production rate. The enhanced photocatalytic performance of CdSe QDs/g-C3N4 can be attributed to the synergistic effects of excellent visible absorption and high charge separation efficiency from the heterostructure. This work could not only provide a facile method to fabricate semiconductor QDs-modified g-C3N4 photocatalysts but also contribute to the design for heterostructures.

Enhanced visible-light response of metal-free doped bulk h-BN as potential efficient photocatalyst: a computational study.

We have provided a straightforward route to screen a series of metal-free doped bulk h-BN as potential visible-light photocatalysts via the first-principle computations. Various nonmetal dopants are considered including Si, P, C, S, Cl, O, and F atoms according to increasing electronegativity. The results show that the introduction of nonmetals leads to small lattice distortions but significant modifications of band structures, electron transition paths and chemical bonding interactions. Generally, all doped h-BN except Si doping have an active response to the visible-light, and dopants with higher electronegativity can significantly narrow the band gaps, which could induce easier optical transition under visible-light excitation. Based on the electronic structures and absorption spectra, three different mechanisms of enhanced visible-light response for the doping effect are proposed. It is expected that F, Cl, and S-doped h-BN could be used as potential efficient visible-light driven photocatalysts. This study could aid in the design of novel efficient h-BN photocatalysts. Graphical Abstract The mechanisms of the enhanced visible-light response of metal-free doped bulk h-BN.

Mechanistic insights into CO2 reduction on Cu/Mo-loaded two-dimensional g-C3N4(001).

In this study, DFT-D calculations were performed to explore the role of Cu and Mo loading in the CO2 conversion mechanism on a two-dimensional g-C3N4(001) surface. The introduced transition metals, Cu and Mo, significantly changed the electron distribution and band structures of g-C3N4. Moreover, two possible mechanisms for the reduction of CO2 to CO have been discussed in detail. We found that the energy barriers of the two mechanisms were largely reduced by Cu and Mo loading, and the dominant reaction path changed on different transition metal-loaded surfaces. Cu/g-C3N4(001) prefers to directly dissociate CO2 into CO, whereas cis-COOH is the preferred product of CO2 reduction on Mo/g-C3N4(001). Considering the activation barrier and reaction route selectivity, Mo-doped g-C3N4(001) was identified as a promising candidate for CO2 conversion. It is concluded that suitable transition metal doping can efficiently reduce the energy barrier and control route selectivity along the reaction paths over the g-C3N4 surface. These findings could provide a helpful understanding of the CO2 reduction mechanisms and aid in the molecular design of novel g-C3N4 catalysts for CO2 conversion.

Oxygen vacancies as active sites for H2S dissociation on the rutile TiO2(110) surface: a first-principles study.

Spin-polarized DFT+U computations have been performed to investigate the role of oxygen vacancies in dissociating H2S on the rutile TiO2(110) surface. A bridged O2c atom is demonstrated to be the most energetically favorable oxygen vacancy site, which makes V(O2c) an electron donator center and induces an isolated defect level with narrowed band gaps. A H2S molecule is adsorbed dissociatively over V(O2c), but molecularly on the perfect surface. For H2S dissociation, the HS/H intermediate state reveals the best thermal stability on both defected and perfect surfaces. Moreover, potential energy surface analysis shows that V(O2c) reduces markedly the energy barriers for the paths along H2S dissociation. This indicates oxygen vacancies to be efficient trap centers for H2S dissociation, as evidenced by a significant interfacial charge transfer promoted by vacancies. This work could provide insights into the role of oxygen vacancies in facilitating the decomposition of H2S on rutile TiO2(110) surface.