Adsorbed hydrogenated N-heterocycles have been proposed as co-catalysts in the mechanism of pyridine (Py)-catalyzed CO reduction over semiconductor photoelectrodes. Initially, adsorbed dihydropyridine (DHP*) was hypothesized to catalyze CO reduction through hydride and proton transfer. Formation of DHP* itself, by surface hydride transfer, indeed any hydride transfer away from the surface, was found to be kinetically hindered. Consequently, adsorbed deprotonated dihydropyridine (2-PyH *) was then proposed as a more likely catalytic intermediate because its formation, by transfer of a solvated proton and two electrons from the surface to adsorbed Py, is predicted to be thermodynamically favored on various semiconductor electrode surfaces active for CO reduction, namely GaP(111), CdTe(111), and CuInS (112). Furthermore, this species was found to be a better hydride donor for CO reduction than is DHP*. Density functional theory was used to investigate various aspects of 2-PyH * formation and its reaction with CO on GaP(110), a surface found experimentally to be more active than GaP(111). 2-PyH * formation was established to also be thermodynamically viable on this surface under illumination. The full energetics of CO reduction through hydride transfer from 2-PyH * were then investigated and compared to the analogous hydride transfer from DHP*. 2-PyH * was again found to be a better hydride donor for CO reduction. Because of these positive results, full energetics of 2-PyH * formation were investigated and this process was found to be kinetically feasible on the illuminated GaP(110) surface. Overall, the results presented in this contribution support the hypothesis of 2-PyH *-catalyzed CO reduction on p-GaP electrodes.

Knowledge of a semiconductor electrode’s band edge alignment is essential for optimizing processes that occur at the semiconductor/electrolyte interface. Photocatalytic processes are particularly sensitive to such alignments, as they govern the transfer of photoexcited electrons or holes from the surface to reactants in the electrolyte solution. Reconstructions of a semiconductor surface during operation, as well as its interaction with the electrolyte solution, must be considered when determining band edge alignment. Here, we employ density functional theory + U theory to assess the stability of reconstructed CuInS2 surfaces, a system which has shown promise for the active and selective photoelectrocatalytic reduction of CO2 to CH3OH. Using many-body Green’s function theory combined with calculations of surface work functions, we determine band edge positions of explicitly solvated, reconstructed CuInS2 surfaces. We find that there is a linear relationship between band edge position and net surface dipole, with the most stable solvent/surface structures tending to minimize this dipole because of generally weak interactions between the surface and solvating water molecules. We predict a conduction band minimum (CBM) of the solvated, reconstructed CuInS2 surface of −2.44 eV vs vacuum at the zero-dipole intercept of the dipole/CBM trendline, in reasonable agreement with the experimentally reported CBM position at −2.64 eV vs vacuum. This methodology offers a simplified approach for approximating the band edge positions at complex semiconductor/electrolyte interfaces.

owned to remarkable physical and chemical properties. [1] As for both scientific and industrial interests, Ni-catalyzed chemical vapor deposition (CVD) is the widely used for its high yields and low cost. [2] Whereas, fabricating carbon materials with welldefined structure, e.g., specific stacking layers and helical angle, is still challenging due to the insufficient knowledge on dynamics control of carbon growth. [3] On the other hand, in catalysis reactions where nickel is involved, the outstanding ability of CC reforming and hydrogen activation ensures ideal catalytic performance of cracking and hydrogenation, but simultaneously suffering from coking due to uncontrollable carbon formation. [4] Numerous solutions have been applied to restrain the unwanted carbon growth but bring limited efficiency. [5] Therefore, from perspectives of either facilitating catalytic reaction of long-term stability with minimized coking, or fabricating carbon materials of specific layers and stacking architecture, it is of high importance to control the migration and coupling processes of carbon atoms in Ni catalyst based on well understanding about reaction dynamics. [6] Although Ni-catalyzed carbon growth has been studied in previous research, detailed knowledge is still ambiguous, Benefitting from outstanding ability of CC reforming and hydrogen activation, nickel is widely applied for heterogeneous catalysis or producing high-quality carbon structures. This high activity simultaneously induces uncontrollable carbon formation, known as coking. However, the activity origin for growing carbon species remains in debate between the on metallic facets induction and nickel carbide segregation. Herein, carbon growth on Ni catalyst is tracked via in situ microscopy methods. Evidence derived from high-resolution transmission electron microscopy imaging, diffraction, and energy loss spectroscopy unambiguously identifies Ni 3 C as the active phase, as opposed to metallic Ni nickel or surface carbides as traditionally believed. Specifically, Ni 3 C particle grows carbon nanofibers (CNF) layer-by-layer through synchronized oscillation of tip stretch and atomic step fluctuations. There is an anisotropic stress distribution in Ni 3 C that provides the lifting force during nanofiber growth. Density functional theory computations show that it is thermodynamically favorable for Ni 3 C to decompose into Ni and surface-adsorbed carbon. Carbonaceous deposits aggregate asymmetrically round the particle because partial surface is exposed to the hydrocarbon environment whereas the bottom side is shielded by the support. This induces a carbon concentration gradient within the particle, which drives C migration through Ni 3 C phase before it exits as CNF growth.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/smtd.202200235. IntroductionControllable synthesis of carbon materials, e.g., nanotubes (CNTs) and graphene, with desired structures attracts much attention

Heterogeneous catalysts featuring metal particles dispersed on an oxide support play an indispensable role in numerous industrial chemical processes. The petrochemical industry relies on supported metal-oxide catalysts for processes that generate industrial chemical feedstocks by reforming the useful byproducts of fossil fuel refinement. Furthermore, many clean energy technologies rely on supported metal-oxide catalysts for the treatment of combustion exhaust and for high-temperature fuel cell applications. Examples of supported metal-oxide catalysis include: catalytic combustion, 1-12 hydrocarbon steam-reforming, 13-24 CO removal from syngas via the water-gas-shift (WGS) reaction, 25-34 CO and NO oxidation, 35-41 automotive three-way catalysis, 42-46 solid oxide fuel cell (SOFC) electrodes, 47-53 and selective hydrogenation. 54-59 The activity and RSC Catalysis Series No. 14 Computational Catalysis Edited by Aravind Asthagiri and Michael J. Janik