Sean Campbell Smith

The Fermi level is a foundational concept in materials science, holding great importance in understanding the electronic and chemical properties of different structures. For materials with charge-density-free regions, determining the Fermi level position using traditional ab initio periodic calculations is accurate only under neutral supercell conditions. The reason is that the introduction of additional charges within the supercell triggers an automatic distribution of a homogeneous compensating background charge (CBC), tasked with maintaining electrical neutrality and avoiding unphysical interactions between the periodic copies of the supercell, which makes the vacuum potential no longer well-defined as a reliable standard energy reference. Here, by employing the virtual crystal approximation (VCA) implemented within density functional theory (DFT), we develop a crystal-structureindependent method to negatively charge the bulk region enclosed by hydrogen atoms, successfully reducing the effects of spurious electrostatic interactions in the vacuum spacing while ensuring a constant Z-plane-averaged electrostatic potential (PAEP). We test this method on graphene and molybdenum disulfide (MoS2) as atomically thin two-dimensional (2D) systems and demonstrate that this method can achieve reasonable agreement with Fermi level determination techniques such as post-processing DFT numerical techniques and DFT-independent finite-element method simulations.

Precise modulation of the electronic structure in transition metals, particularly the d-band center position and spin state, remains a critical challenge to expediting hydrogen evolution reaction (HER) kinetics. Herein, we report a NiPt/Ni-heterostructured catalyst enabling simultaneous optimization of the d-band electronic structure and spin state of Ni through regulation of the NiPt and Ni bridge sites. Combining operando spectroscopy, X-ray absorption spectroscopy, density functional theory, and ab initio molecular dynamics simulations, we establish that the coordination environment and spin states of Ni at the bridge sites were effectively modulated by altering the Pt content, achieving a transition of Ni centers from the low-spin to high-spin state, and optimized intermediate adsorption/desorption behaviors. The resulting NiPt/Ni catalyst exhibits an exceptional HER performance in acidic media, achieving a benchmark current density of -10 mA cm^-2 at a mere 9.8 mV overpotential and delivering an industrial-scale 1.0 A cm^-2 current density in PEM electrolysis at 1.75 V.

Setting out from previous work, an analytic description of regular wurtzite‐ (w‐) structure nanowires (NWires) is extended by introducing morphing terms to describe arbitrary convex cross sections featuring linear interfaces as encountered in experiment. Add‐on terms to the existing number series of regular cross sections are provided with their respective running indices, yielding the required flexibility for cross section morphing. The main variables are the number of NWire atoms , bonds between NWire atoms and interface bonds as a function of NWire size and shape, complemented by other basic geometric variables such as specific lengths of interface facets, as well as widths, heights, and total area of the cross section. Cross section morphing is demonstrated for the three high symmetry w‐NWires with low‐index faceting frequently occurring in NWire processing. The fundamental insights revealed here offer a universal gauge and thus enable major advancements in data interpretation and understanding of above‐mentioned w‐structure based NWires with arbitrary convex cross sections. As a corroborating example, a precise description of an irregular w‐GaAs/w‐Ge core/shell NWire cross section is given, whereby a radially changing lattice constant can be included.

Corrections to the article by König & Smith [Acta Cryst. (2022), B78, 665–677] are given.

Single-atom catalysts (SACs) have become the forefront and hotspot in energy storage and conversion research, inheriting the advantages of both homogeneous and heterogeneous catalysts. In particular, carbon-supported SACs (CS-SACs) are excellent candidates for many energy storage and conversion applications, due to their maximum atomic efficiency, unique electronic and coordination structures, and beneficial synergistic effects between active catalytic sites and carbon substrates. In this review, we briefly review the atomic-level regulation strategies for optimizing CS-SACs for energy storage and conversion, including coordination structure control, nonmetallic elemental doping, axial coordination design, and polymetallic active site construction. Then we summarize the recent progress of density functional theory studies on designing CS-SACs by the above strategies for electrocatalysis, such as hydrogen evolution reaction, oxygen evolution reaction, oxygen reduction reaction, CO₂ reduction reaction, nitrogen reduction reaction, and electrosynthesis of urea, and electrochemical energy storage systems such as monovalent metal–sulfur batteries (Li–S and Na–S batteries). Finally, the current challenges and future opportunities in this emerging field are highlighted. This review will provide a helpful guideline for the rational design of the structure and functionality of CS-SACs, and contribute to material optimizations in applications of energy storage and conversion.

Crystalline nanowire (NWire) cross‐section shapes are known to vary considerably in experiment; an accurate analytic evaluation of NWire cross‐sections from a thermodynamic perspective is still missing. Building on previous work, analytic descriptions are given for zincblende (zb) NWire cross‐section morphing to arbitrary convex hexagonal shapes in order to evaluate the crystallographic‐structural stability of experimental NWire cross‐sections. The maximum of the ratio of NWire‐internal bonds per NWire atom describes the most stable crystallographic and thermodynamic shape of the NWire as far as internal forces are concerned. This maximum occurs when the first derivative of the above ratio , with presenting respective optimum morphing indices to obtain . The stability evaluation is then carried out by comparing derived from the experimental image over the complete morphing range of the NWire cross‐section represented by . This user‐friendly analytic approach allows to calculate the optimum morphing indices and thus all follow‐on parameters, such as , , the number of interface bonds and the NWire cross‐section area . Three examples with experimental data demonstrate the versatility and detailed insight the stability evaluation provides to any zb‐ and diamond‐lattice NWire cross‐section.

Co-adsorbed hydroxyl species play a significant role in changing the energy landscape of the plasmon-mediated CO ₂ reaction. These promote CO ₂ activation and transfer of hot electrons in newly formed hybridized orbitals, thereby improving selectivity.

Electrocatalytic urea synthesis through N₂ + CO₂ coreduction and C-N coupling is a promising and sustainable alternative to harsh industrial processes. Despite considerable efforts, limited progress has been made due to the challenges of breaking inert N≡N bonds for C-N coupling, competing side reactions, and the absence of theoretical principles guiding catalyst design. In this study, we propose a mechanism for highly electrocatalytic urea synthesis using two adsorbed N₂ molecules and CO as nitrogen and carbon sources, respectively. This mechanism circumvents the challenging step of N≡N bond breaking and selective CO₂ to CO reduction, as the free CO molecule inserts into dimerized *N₂ and binds concurrently with two N atoms, forming a specific urea precursor *NNCONN* with both thermodynamic and kinetic feasibility. Through the proposed mechanism, Ti₂@C₄N₃ and V₂@C₄N₃ are identified as highly active catalysts for electrocatalytic urea formation, exhibiting low onset potentials of -0.741 and -0.738 V, respectively. Importantly, taking transition metal atoms anchored on porous graphite-like carbonitride (TM₂@C₄N₃) as prototypes, we introduce a simple descriptor, namely, effective d electron number (Φ), to quantitatively describe the structure-activity relationships for urea formation. This descriptor incorporates inherent atomic properties of the catalyst, such as the number of d electrons, the electronegativity of the metal atoms, and the generalized electronegativity of the substrate atoms, making it potentially applicable to other urea catalysts. Our work advances the comprehension of mechanisms and provides a universal guiding principle for catalyst design in urea electrochemical synthesis.