Revealing the Volcano-Shaped Activity Trend of Triiodide Reduction Reaction: A DFT Study Coupled with Microkinetic Analysis

Bubble-water/catalyst triphase interface microenvironment accelerates photocatalytic OER via optimizing semi-hydrophobic OH radical

Photocatalytic water splitting (PWS) as the holy grail reaction for solar-to-chemical energy conversion is challenged by sluggish oxygen evolution reaction (OER) at water/catalyst interface. Experimental evidence interestingly shows that temperature can significantly accelerate OER, but the atomic-level mechanism remains elusive in both experiment and theory. In contrast to the traditional Arrhenius-type temperature dependence, we quantitatively prove for the first time that the temperature-induced interface microenvironment variation, particularly the formation of bubble-water/TiO2(110) triphase interface, has a drastic influence on optimizing the OER kinetics. We demonstrate that liquid-vapor coexistence state creates a disordered and loose hydrogen-bond network while preserving the proton transfer channel, which greatly facilitates the formation of semi-hydrophobic •OH radical and O-O coupling, thereby accelerating OER. Furthermore, we propose that adding a hydrophobic substance onto TiO2(110) can manipulate the local microenvironment to enhance OER without additional thermal energy input. This result could open new possibilities for PWS catalyst design.

Topology-Determined Structural Genes Enable Data-Driven Discovery and Intelligent Design of Potential Metal Oxides for Inert C-H Bond Activation

The identification of appropriate structural genes that influence the active-site configuration for a given reaction is critical for discovering potential catalysts with reduced reaction barriers. In this study, we introduce bulk-phase topology-derived tetrahedral descriptors as a means of expressing a catalyst's "material structural genes". We combine this approach with an interpretable machine learning model to accurately and efficiently predict the effective barrier associated with methane C-H bond cleavage across a wide range of metal oxides (MOs). These structural genes enable high-throughput catalyst screening for low-temperature methane activation and ultimately identify 13 candidate catalysts from a pool of 9095 MOs that are recommended for experimental synthesis. The topology-based method that we describe can also be extended to facilitate high-throughput catalyst screening and design for other dehydrogenation reactions.

CATKINAS: A large-scale catalytic microkinetic analysis software for mechanism auto-analysis and catalyst screening

As an effective method to analyze complex catalytic reaction networks, microkinetic modeling is gaining increasing popularity in the catalytic activity evaluation and rational design of heterogeneous catalysts. An automated simulator with stable and reliable performance is especially useful and in great request. Here we introduce the CATKINAS package developed for large-scale microkinetic modeling and analysis. Featuring with a multilevel solver and a multifunctional analyzer, CATKINAS can provide both accurate solutions and various quantitative and automatic analysis for a wide range of catalytic systems. The structure and the basic workflow are overviewed with the multilevel solver particularly illustrated. Also, we take the CO methanation reaction as an example to illustrate the application and efficiency of the CATKINAS package.

A DFT+U revisit of reconstructed CeO2(100) surfaces: structures, thermostabilities and reactivities

Cerium dioxide (CeO2) shows wide catalytic applications by virtue of its excellent oxygen storage capacity. The CeO2(100) surface has aroused particular interest because of its intrinsic polarity; however, it suffers from structural reconstruction, which consequently hinders experimental and theoretical studies. In this work, we performed density functional theory calculations with on-site Coulomb interaction correction to investigate and further correlate the geometric and catalytic properties of reconstructed CeO2(100) surfaces. By introducing CeO2 units on a previous O-terminal model, the surface exposed CeO4 pyramids with gradual increase in coverage and eventually transformed into a Ce-terminal structure. The corresponding thermostabilities were evaluated by calculating the surface energy and oxygen vacancy formation energy. We also showed that the CO oxidation on the reconstructed CeO2(100) surfaces favored the Mars-van-Krevelen mechanism. The most stable CeO4-terminal type of reconstruction, covered with a half overlayer of CeO4 pyramids on the surface, was capable of directly producing CO2 without forming bent CO2 intermediates and carbonate byproducts. Moreover, coordinatively unsaturated Ce ions at the pyramid apex provided extra accommodation to the reacting CO, thus lowering the reaction barrier of the key CO coupling step relative to that of the O-terminal surface. We finally generalized a unified picture of the dynamic changes in the thermostability and catalytic activity along with the structural reconstruction of the CeO2(100) surface. The CeO4-terminal type of reconstruction was theoretically predicted to be highly efficient for catalyzing CO oxidation.

Theoretical investigation of oxidation of NO (NO + ½ O2 → NO2) on surfaces of nickel-doped nanocages (Ni-C60 and Ni-B30N30)

In present study, the NO oxidation on Ni-carbon nanocage and Ni-boron nitride nanocage surfaces was investigated. The Ni-C₆₀ and Ni-B₃₀N₃₀ catalysts can oxidize the NO molecule by Langmuir-Hinshelwood (LH) and Eley-Rideal (ER) mechanisms. In this study, the NO molecule was joined to Ni atom of the Ni-surface-O₂* and Ni-surface-O* to generate the intermediates with low barrier energies. It can be concluded that the cis-Ni-surface-ONOO* complex in the ER pathway is more stable than four-elements-ring complex in LH pathway ca 0.06 and 0.08 eV, respectively. In the LH pathway, the studied catalysts were deactivated by irreversible absorption of NO₂ molecules in Ni atoms of Ni-C₆₀ and Ni-B₃₀N₃₀. In contrast, in the ER pathway two NO₂ molecules were released in the normal temperature. In this study, the abilities of the Ni-C₆₀ and Ni-B₃₀N₃₀ to oxidation of NO molecule was demonstrated. Finally, the systematic scheme to design of metal-doped nano-catalysts to oxidation of toxic gases was proposed.

Recent Progress in the Design and Synthesis of Nitrides for Mesoscopic and Perovskite Solar Cells

With growing concerns about global warming and the energy crisis, a variety of photovoltaic devices have attracted worldwide attention as alternative energy sources. Among them, organic-inorganic hybrid photovoltaics, typically mesoscopic and perovskite solar cells, are promising, owing to their potential for low-cost energy production, which mainly comes from unlimited combinations of materials optimized for each step of solar energy conversion. However, the commercialization of organic-inorganic hybrid solar cells is hampered by costly electrocatalysts or hole-transport materials. Currently, state-of-the-art dye- or quantum-dot-sensitized solar cells and perovskite solar cells necessitate noble metals and high-price polymeric materials. In an attempt to resolve this issue, various kinds of metal compounds have been investigated, and nitrides have been actively reported to possess a number of favorable properties for the aforementioned purpose, such as excellent electrical conductivity and superb electrocatalytic performance. Herein, the use of nitrides as cost-effective electrocatalysts or hole-transport materials in organic-inorganic hybrid solar cells is reviewed. Nitrides with a variety of morphologies and scales are discussed, together with the synergistic effect in the case of diverse composites. In addition, prospects and challenges for applying nitride materials are briefly suggested.

Element substitution of kesterite Cu2ZnSnS4 for efficient counter electrode of dye-sensitized solar cells

Development of cost-effective counter electrode (CE) materials is a key issue for practical applications of photoelectrochemical solar energy conversion. Kesterite Cu₂ZnSnS₄ (CZTS) has been recognized as a potential CE material, but its electrocatalytic activity is still insufficient for the recovery of I^-/I₃^- electrolyte in dye-sensitized solar cells (DSSCs). Herein, we attempt to enhance the electrocatalytic activity of kesterite CZTS through element substitution of Zn²⁺ by Co²⁺ and Ni²⁺ cations, considering their high catalytic activity, as well as their similar atomic radius and electron configuration with Zn²⁺. The Cu₂CoSnS₄ (CCTS) and Cu₂NiSnS₄ (CNTS) CEs exhibit smaller charge-transfer resistance and reasonable power conversion efficiency (PCE) (CCTS, 8.3%; CNTS, 8.2%), comparable to that of Pt (8.3%). In contrast, the CZTS-based DSSCs only generate a PCE of 7.9%. Density functional theory calculation indicate that the enhanced catalytic performance is associated to the adsorption and desorption energy of iodine atom on the Co²⁺ and Ni²⁺. In addition, the stability of CCTS and CNTS CEs toward electrolyte is also significantly improved as evidenced by X-ray photoelectron spectroscopy and electrochemical impedance spectroscopy characterizations. These results thus suggest the effectiveness of the element substitution strategy for developing high-performance CE from the developed materials, particularly for multicomponent compounds.

Highly Efficient Bifacial Dye-Sensitized Solar Cells Employing Polymeric Counter Electrodes

Dye-sensitized solar cells (DSCs) are promising solar energy conversion devices with aesthetically favorable properties such as being colorful and having transparent features. They are also well-known for high and reliable performance even under ambient lighting, and these advantages distinguish DSCs for applications in window-type building-integrated photovoltaics (BIPVs) that utilize photons from both lamplight and sunlight. Therefore, investigations on bifacial DSCs have been done intensively, but further enhancement in performance under back-illumination is essential for practical window-BIPV applications. In this research, highly efficient bifacial DSCs were prepared by a combination of electropolymerized poly(3,4-ethylenedioxythiphene) (PEDOT) counter electrodes (CEs) and cobalt bipyridine redox ([Co(bpy)₃]^3+/2+) electrolyte, both of which manifested superior transparency when compared with conventional Pt and iodide counterparts, respectively. Keen electrochemical analyses of PEDOT films verified that superior electrical properties were achievable when the thickness of the film was reduced, while their high electrocatalytic activities were unchanged. The combination of the PEDOT thin film and [Co(bpy)₃]^3+/2+ electrolyte led to an unprecedented power conversion efficiency among bifacial DSCs under back-illumination, which was also over 85% of that obtained under front-illumination. Furthermore, the advantage of the electropolymerization process, which does not require an elevation of temperature, was demonstrated by flexible bifacial DSC applications.

Alkaline-promoted Ni based ordered mesoporous catalysts with enhanced low-temperature catalytic activity toward CO2 methanation

Mg alkaline-promoted Ni ordered mesoporous catalysts possess enhanced catalytic activities and stabilities toward CO₂ methanation due to decreasing CO₂ activation energy.