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We have studied the decomposition of methanol-d4 on thin film Al2O3/NiAl(100) under near-ambient-pressure conditions, with varied surface-probe techniques and calculations based on density-functional theory. Methanol-d4 neither adsorbed nor reacted on Al2O3/NiAl(100) at 400 K under ultrahigh vacuum conditions, whereas they dehydrogenated, largely to methoxy-d3 (CD3O*, * denoting adsorbates) and formaldehyde-d2 (CD2O*), on the surface when the methanol-d4 partial pressure was increased to 10−3 mbar and above. The dehydrogenation was facilitated by hydroxyl (OH* or OD*) from the dissociation of little co-adsorbed water; a small fraction of CD2O* interacted further with OH* (OD*) to form, via intermediate CD2OOH* (CD2OOD*), formic acid (DCOOH* or DCOOD*). A few surface carbonates were also yielded, likely on the defect sites of Al2O3/NiAl(100). The results suggest that alumina not only supports metal clusters but also participates in reactions under realistic catalytic conditions. One may consider accordingly the multiple functions of alumina while designing ideal catalysts. [ABSTRACT FROM AUTHOR]

While germanium‐based anodes for Li‐ion batteries (LIBs) have potential to offer high energy density, their commercialization is impeded by low ionic and electronic conductivity and poor tolerance to volume change during cycling. Here a new quaternary CuGeSiP3 anode is reported to simultaneously overcome these limitations. Synthesized via ball milling process, CuGeSiP3 displays high ionic and electronic conductivity and excellent flexibility to accommodate volume change, attributed to increased structural entropy and reversible formation of favorable intermediates of both electronic and Li ion conductors, as confirmed by experimental measurements and theoretical calculations. When used as an LIB anode, CuGeSiP3 demonstrates large reversible capacity, high Coulombic efficiency, robust cycling stability, and high‐rate capability because it undergoes a reversible lithiation process that involves intercalation and conversion reaction. When composited with layered graphite, the electrode demonstrates exceptional cycling stability (1 261 mA h g−1 after 600 cycles at 400 mA g−1 and 861 mA h g−1 after 1 450 cycles at 20 00 mA g−1) and ultrahigh rate capability (448 mA h g−1 at 20 000 mA g−1). Further, the quaternary, pentanary, and hexanary cation‐disordered phosphides are also synthesized, all having similar Li‐storage superiority, implying the multiple co‐doping strategy is applicable to other material systems. [ABSTRACT FROM AUTHOR]

The development of low‐cost, high‐power lithium‐ion batteries requires durable anode materials that can store and release lithium quickly. Here a mixed phase of H‐Nb2O5 and M‐Nb2O5 (denoted as d‐H,M‐Nb2O5) that demonstrates excellent performance as an anode material for lithium storage is reported. Experimental and computational analyses reveal several salient features of d‐H,M‐Nb2O5. First, the edge‐sharing arrangement between the mixed niobium oxygen polyhedral block structures helps alleviate volume expansion during cycling, thereby enhancing stability and reversibility. Second, the mixed‐phase structure facilitates a continuous pathway for lithium ion adsorption These characteristics allow for sequential transport of lithium ions, enabling fast charging. As a result, the d‐H,M‐Nb2O5 electrode material exhibits a high capacity of 142 mAh g−1 at an ultra‐fast charging rate of 100 C, while maintaining 85% of its initial capacity after 5000 cycles. Moreover, its practical feasibility is established by demonstrating full‐cell performance at a 5 C discharge/charge rate (13 mA cm−2), maintaining 79% of its capacity over 1000 cycles. [ABSTRACT FROM AUTHOR]

The decomposition of methanol-d4 (CD3OD) on Rh nanoclusters grown by the deposition of Rh vapors onto an ordered thin film of Al2O3/NiAl(100) was studied, with various surface-probe techniques and largely under near-ambient-pressure (NAP) conditions. The results showed a superior reactivity of small Rh clusters (diameter < 1.5 nm) exposed to CD3OD at 5 × 10−3–0.1 mbar at 400 K; the gaseous production of CO and D2 from decomposed methanol-d4 per Rh surface site on the small Rh clusters with diameters of ∼1.1 nm was nearly 8 times that on large ones with diameters of ∼3.5 nm. The promotion of reactivity with decreased cluster size under NAP conditions was evidently greater than that under ultrahigh vacuum conditions. Moreover, the concentration of atomic carbon (C*; where * denotes adsorbate)—a key catalyst poisoner—yielded from the dissociation of CO* from dehydrogenated methanol-d4 was significantly smaller on small clusters (diameter < 1.5 nm). The NAP size effect on methanol-d4 decomposition involved the surface hydroxyl (OH*) from the little co-adsorbed water (H2O*) that was dissociated at a probability dependent on the cluster size. H2O* was more likely dissociated into OH* on small Rh clusters, by virtue of their more reactive d-band structure, and the OH* then effectively promoted the O–D cleavage of methanol-d4, as the rate-determining step, and thus the reaction probability; on the other hand, the OH* limited CO* dissociation on small Rh clusters via both adsorbate and lateral effects. These results suggest that the superior properties of small Rh clusters in both reactivity and anti-poisoning would persist and be highly applicable under "real-world" catalysis conditions. [ABSTRACT FROM AUTHOR]

We studied the dissociation of water (H2O*, with * denoting adspecies) on atomic oxygen (O*)-covered Rh nanoclusters (RhO*) supported on a graphene film grown on a Ru(0001) surface [G/Ru(0001)] under ultrahigh-vacuum conditions and with varied surface-probe techniques and calculations based on density-functional theory. The graphene had a single rotational domain; its lattice expanded by about 5.7% to match the Ru substrate structurally better. The Rh clusters were grown by depositing Rh vapors onto G/Ru(0001); they had an fcc phase and grew in (111) orientation. Water adsorbed on the Rh clusters was dissociated exclusively in the presence of O*, like that on a Rh(111) single-crystal surface. Contrary to the case on Rh(111)O*, excess O* (even at a saturation level) on small RhO* clusters (diameter of 30–34 Å) continued to promote, instead of inhibiting, the dissociation of water; the produced hydroxyl (OH*) increased generally with the concentration of O* on the clusters. The difference results from more reactive O* on the RhO* clusters. O* on RhO* clusters activated the dissociation via both the formation of hydrogen bonds with H2O* and abstraction of H directly from H2O*, whereas O* on Rh(111)O* assisted the dissociation largely via the formation of hydrogen bonds, which was readily obstructed with an increased O* coverage. As the disproportionation (2 OH* → H2O* + O*) is endothermic on the RhO* clusters but exothermic on Rh(111)O*, OH* produced on RhO* clusters showed a thermal stability superior to that on the Rh(111)O* surface—thermally stable up to 400 K. [ABSTRACT FROM AUTHOR]

Pt and Rh nanoclusters, grown on deposition of Pt and Rh vapors onto graphene/Pt(111), show separate reactivity toward the decomposition of methanol-d4. The Pt (Rh) clusters had a mean diameter 2.0–3.5 nm (2.1–4.0 nm) and height 0.45–0.94 nm (0.41–0.9 nm) evolving with the coverage; they were structurally ordered, having an fcc phase and growing in (111) orientation, and had lattice constants similar to their bulk values. Methanol-d4 on the Pt clusters did not decompose but desorbed mostly, disparate from that on Pt(111) surface; the disparity arose as the adsorption energies of methanol-d4 on most surface sites of the Pt clusters became smaller than their single crystal counterpart. This size effect, nevertheless, did not apply on the Rh clusters, despite their similar atomic stacking; the Rh clusters showed a reactivity similar to that of the Rh(111) surface because the adsorption energies of methanol-d4 on both Rh clusters and Rh(111) are comparable. The distinct size dependence was rationalized through their electronic structures and charge distribution of Fukui function mapping. Our results suggest that reactive transition metals do not necessarily become more reactive while they are scaled down to nanoscale; their reactivity evolves with their size in a manner largely dependent on their electronic nature. [ABSTRACT FROM AUTHOR]

Despite the high volumetric capacity of Ge-based anodes, their practical applications are still limited by low cycling stability and rate performance. To resolve these challenges, herein, we simultaneously incorporate both Al and P into Ge to synthesize AlGexP (x = 6, 2, 2/3) series materials through a facile mechanical ball milling method. Experiments and theoretical calculations confirm that AlGe2P provides the fastest electronic conductivity and Li-ion diffusion capability, thus providing the best Li-storage performance among AlGexP (x = 6, 2, 2/3) series materials. As verified by ex situ characterization, AlGe2P features a reversible Li-storage mechanism arising from the first intercalation stage followed by conversion reactions, where the electronically conducting Li15GeP3, Li4.4Ge, and LiAl and Li-ion conducting Li3P, Li4.4Ge and LiAl are simultaneously produced, ensuring fast charge storage kinetics upon cycling. Accordingly, the AlGe2P/C composite presents a long-term cycling stability of retaining 867 mA h g−1 after 800 cycles at 2000 mA g−1, and a high-rate capacity of 454 mA h g−1 even at 20 000 mA g−1, thus holding promise for real world applications. Broadly, the ternary all-lithium-reactive Ge-based compounds have great application potential in the energy storage field due to their intriguing physiochemical properties. [ABSTRACT FROM AUTHOR]