Molten-Salt Electrochemical-Assisted Synthesis of the CeO2-OV@GC Composite-Supported Pt Clusters with a Pt-O-Ce Structure for the Oxygen Reduction Reaction.

Highly active and robust Pt-based electrocatalysts for an oxygen reduction reaction (ORR) are of crucial significance for the development of proton exchange membrane fuel cells (PEMFCs). Herein, the high-loading and well-dispersive Pt clusters on graphitic carbon-supported CeO2 with abundant oxygen vacancies (PtAC/CeO2-OV@GC) were successfully fabricated by a molten-salt electrochemical-assisted method. The bonding of Pt with the highly electronegative O induces charge redistribution through the Pt-O-Ce structure, thus reducing the adsorption energies of oxygen-containing species. Such a PtAC/CeO2-OV@GC electrocatalyst exhibits a greatly enhanced ORR performance with a mass activity of 0.41 ± 0.02 A·mg-1Pt at 0.9 V versus a reversible hydrogen electrode, which is 2.7 times the value of a commercial Pt/C catalyst and shows negligible activity decay after 20000 cycles of accelerated degradation tests. It is anticipated that this work will provide enlightening guidance on the controllable synthesis and rational design of high-performance Pt-based electrocatalysts for PEMFCs.

Reactivity of surface oxygen vacancy sites and frustrated Lewis acid-base pairs of In2O3 catalysts in CO2 hydrogenation.

The effects of oxygen vacancy (VO) formation energy and surface frustrated Lewis acid-base pairs (SFLPs) on the CO2 hydrogenation activity of In2O3 catalysts were studied using density functional theory calculations. The VO formation energy of 2.8-3.3 eV was found to favor HCOO formation, whereas the presence of SFLPs is conducive to CO formation.

Outcomes and adverse events for spinal synovial cysts surgical treatment: a systematic review and meta-analysis.

BACKGROUND: Spinal synovial cysts (SSCs) are a rare cause of nerve root and spinal cord compression. Surgical excision of SSCs remains the mainstay of treatment in the presence of unremitting symptoms or neurological deficits, but the choice of the surgical approach remains controversial. The goal of this study was to compare clinical outcomes and adverse events associated with traditional approaches (interlaminar or laminectomy/hemilaminectomy) and minimally invasive approaches (microsurgical tubular approaches or endoscopic approaches) for SSCs. METHODS: Studies reporting surgical management of SSCs were searched in three online databases (PubMed, the Cochrane Library, and Web of Science). This meta-analysis was reported following the PRISMA Statement. It was registered at the International Prospective Register of Systematic Reviews (CRD42021288992). The Cochrane Collaboration's Risk of Bias in Nonrandomised Studies-of Interventions (ROBINS-I) was used to evaluate bias. Extracted research data were statistically analyzed using Stata 16 and SPSS statistics 25. RESULTS: A total of 22 related relevant studies were included. Meta-analysis revealed no statistically significant difference in dural tear, residual cyst, recurrence, reoperation, and operation time between minimally invasive approaches and traditional approaches (p > 0.05), but minimally invasive approaches had a good functional improvement (p = 0.004). Postoperative length of hospital stays and intraoperative bleeding in traditional approaches were also higher than in minimally invasive approaches (p < 0.05). CONCLUSION: Based on the available evidence, minimally invasive approaches may be better than traditional approaches in the treatment of SSCs. Minimally invasive approaches had the advantages of improving clinical satisfaction, with a similar complication rate to traditional approaches. Moreover, endoscopic and microsurgical tubular approaches had similar outcomes.

Molten-Salt Electrochemical Deoxidation Synthesis of Platinum-Neodymium Nanoalloy Catalysts for Oxygen Reduction Reaction.

Platinum-rare earth metal (Pt-RE) nanoalloys are regarded as a potential high performance oxygen reduction reaction (ORR) catalyst. However, wet chemical synthesis of the nanoalloys is a crucial challenge because of the extremely high oxygen affinity of RE elements and the significantly different standard reduction potentials between Pt and RE. Here, this paper presents a molten-salt electrochemical synthetic strategy for the compositional-controlled preparation of platinum-neodymium (Pt-Nd) nanoalloy catalysts. Carbon-supported platinum-neodymium (Ptx Nd/C) nanoalloys, with distinct compositions of Pt5 Nd and Pt2 Nd, are obtained through molten-salt electrochemical deoxidation of platinum and neodymium oxide (Pt-Nd2 O3 ) precursors supported on carbon. The Ptx Nd/C nanoalloys, especially the Pt5 Nd/C exhibit a mass activity of 0.40 A mg-1 Pt and a specific activity of 1.41 mA cm-2 Pt at 0.9 V versus RHE, which are 3.1 and 7.1 times higher, respectively, than that of commercial Pt/C catalyst. More significantly, the Pt5 Nd/C catalyst is remarkably stable after undergoing 20 000 accelerated durability cycles. Furthermore, the density-functional-theory (DFT) calculations confirm that the ORR catalytic performance of Ptx Nd/C nanoalloys is enhanced by compressive strain effect of Pt overlayer, causing a suitable weakened binding energies of O* Δ E O ∗ $\Delta {E}_{{{\rm{O}}}^*}$ and Δ E OH ∗ $\Delta {E}_{{\rm{OH}}^*}$ .

Computational screening of single-atom doped In2O3 catalysts for the reverse water gas shift reaction.

The reverse water gas shift (RWGS) reaction is an important method for converting carbon dioxide (CO2) into valuable chemicals and fuels by hydrogenation. In this paper, the catalytic activity of single-atom metal-doped (M = Pt, Ir, Pd, Rh, Cu, Ni) indium oxide (c-In2O3) catalysts in the cubic phase for the RWGS reaction was investigated using density functional theory (DFT) calculations. This was achieved by identifying metal sites, screening oxygen vacancies, followed by further calculating the energy barriers for the direct and indirect dissociation pathways of the RWGS reaction. Our results show that the single-atom dopant in the indium oxide lattice promotes the creation of oxygen vacancies on the In2O3 surface, thereby facilitating the adsorption and activation of CO2 by the oxide surface and initiating the subsequent RWGS reaction. Furthermore, we find that the oxygen vacancy (OV) formation energy on the surface of the single-atom metal doped c-In2O3(111) surface can be used as a descriptor for CO2 adsorption, and the higher the OV formation energy, the more stable the CO2 adsorption structure is. The Cu/In2O3 structure has relatively high energy barriers for both direct (1.92 eV) and indirect dissociation (2.09 eV) in the RWGS reaction, indicating its low RWGS reactivity. In contrast, the Ir/In2O3 and Rh/In2O3 structures are more conducive to the direct dissociation of CO2 into CO, which may serve as more efficient RWGS catalysts. Furthermore, microkinetic simulations show that single atom metal doping to In2O3 enhances CO2 conversion, especially under high reaction temperatures, where the formation of oxygen vacancies is the limiting factor for CO2 reactivity on the M/In2O3 (M = Cu, Ir, Rh) models. Among these three single-atom catalysts, the Ir/In2O3 model was predicted to have the best CO2 reactivity at reaction temperatures above 573 K.

DFT-based microkinetic studies on methanol synthesis from CO2 hydrogenation over In2O3 and Zr-In2O3 catalysts.

Density functional theory (DFT) calculations and microkinetic simulations were performed to study the structure-performance relationship of In2O3 and Zr-doped In2O3 catalysts for methanol synthesis, focusing on the In2O3(110) and Zr-doped In2O3(110) surfaces. These surfaces are expected to follow the oxygen vacancy-based mechanism via the HCOO route for CO2 hydronation to methanol. Our DFT calcualtions show that the Zr-In2O3(110) surface is more favorable for CO2 adsorption than the In2O3(110) surface, and although the energy barriers are not lowered, most intermediates in the HCOO route are stablized with the introduction of the Zr dopant. Microkinetic simulations suggest that the CH3OH formation rate is improved by ∼10 times and CH3OH selectivity increased significantly from 10% on In2O3(110) to 100% on the Zr1-In2O3(110) catalyst model at 550 K. We find that the higher CH3OH formation rate and CH3OH selectivity on the Zr1-In2O3(110) surface than those on the In2O3(110) surface can be attributed to the slightly increased OV formation energy and the stablization of the reaction intermediates, whereas the much lower CH3OH formation rate on the Zr3-In2O3(110) surface is due to the much higher OV formation energy and the over binding of the H2O at the OV site.

Highly Selective Photoelectroreduction of Carbon Dioxide to Ethanol over Graphene/Silicon Carbide Composites.

Using sunlight to produce valuable chemicals and fuels from carbon dioxide (CO2 ), i.e., artificial photosynthesis (AP) is a promising strategy to achieve solar energy storage and a negative carbon cycle. However, selective synthesis of C2 compounds with a high CO2 conversion rate remains challenging for current AP technologies. We performed CO2 photoelectroreduction over a graphene/silicon carbide (SiC) catalyst under simulated solar irradiation with ethanol (C2 H5 OH) selectivity of>99 % and a CO2 conversion rate of up to 17.1 mmol gcat -1 h-1 with sustained performance. Experimental and theoretical investigations indicated an optimal interfacial layer to facilitate the transfer of photogenerated electrons from the SiC substrate to the few-layer graphene overlayer, which also favored an efficient CO2 to C2 H5 OH conversion pathway.

Water interaction with B-site (B = Al, Zr, Nb, and W) doped SrFeO3-δ-based perovskite surfaces for thermochemical water splitting applications.

Density functional theory (DFT) calculations were performed to study the interaction of water with the SrO and FeO2 terminations of the SrFeO3-δ (001) surface, where the effects of the metal dopants (Al, Zr, Nb, and W), surface oxygen vacancies, and oxygen ion migration were investigated. Our calculations showed that the metal dopants benefited the molecular and dissociative adsorptions of H2O on both the perfect and oxygen-vacancy-containing surfaces. The surface oxygen vacancies were predicted to promote the dissociative adsorption of H2O and the formation of H2. For all structures studied, H2 release was found to be always an overall endothermic process, except for the W-doped structure which will become exothermic at high temperature. On the oxygen-vacancy-containing surface, H2 generation was predicted to be easier at the SrO termination than the FeO2 termination. Furthermore, we also investigated the oxygen ion migration mechanism on all surface structures, predicted the behaviour of oxygen migration and the effect of oxygen vacancy defects. Our results showed that Al doping facilitated not only the formation of surface oxygen vacancies, but also oxygen migration from the surface to the subsurface, in contrast to the Zr, Nb and W-doped structures. This study provided significant insights into the interaction of water with the surfaces of doped SrFeO3-δ perovskite materials for thermochemical water splitting applications.

Tandem Catalysis for Selective Oxidation of Methane to Oxygenates Using Oxygen over PdCu/Zeolite.

Selective oxidation of methane to oxygenates with O2 under mild conditions remains a great challenge. Here we report a ZSM-5 (Z-5) supported PdCu bimetallic catalyst (PdCu/Z-5) for methane conversion to oxygenates by reacting with O2 in the presence of H2 at low temperature (120 °C). Benefiting from the co-existence of PdO nanoparticles and Cu single atoms via tandem catalysis, the PdCu/Z-5 catalyst exhibited a high oxygenates yield of 1178 mmol g-1 Pd h-1 (mmol of oxygenates per gram Pd per hour) and at the same time high oxygenates selectivity of up to 95 %. Control experiments and mechanistic studies revealed that PdO nanoparticles promoted the in situ generation of H2 O2 from O2 and H2 , while Cu single atoms not only accelerated the activation of H2 O2 for the generation of abundant hydroxyl radicals (⋅OH) from H2 O2 decomposition, but also enabled the homolytic cleavage of CH4 by ⋅OH to methyl radicals (⋅CH3 ). Subsequently, the ⋅OH reacted quickly with the ⋅CH3 to form CH3 OH with high selectivity.

A DFT-based microkinetic study on methanol synthesis from CO2 hydrogenation over the In2O3 catalyst.

In this work, we performed density functional theory (DFT)-based microkinetic simulations to elucidate the reaction mechanism of methanol synthesis on two of the most stable facets of the cubic In2O3 (c-In2O3) catalyst, namely the (111) and (110) surfaces. Our DFT calculations show that for both surfaces, it is difficult for the H atom adsorbed at the remaining surface O atom around the O vacancy (Ov) active site to migrate to an O adsorbed at the Ov due to the very high energy barrier involved. In addition, we also find that the C-O bond in the bt-CO2* chemisorption structure can directly break to form CO with a lower energy barrier than that in its hydrogenation to the COOH* intermediate in the COOH route. However, our microkinetic simulations suggest that for both surfaces, CO2 deoxygenation to form CO in both pathways, namely the COOH and CO-O routes, are kinetically slower than methanol formation under typical steady state conditions assuming a CO2 conversion of 10% and a CO selectivity of 1%. Although these results agree with previous experimental observations at relatively low reaction temperature, where methanol formation dominates, they cannot explain the predominant formation of CO at relatively high reaction temperature. We tentatively attribute this to the simplicity of our microkinetic model as well as possible structural changes of the catalyst at relatively high reaction temperature. Furthermore, although the rate-determining step (RDS) from the degree of rate control (DRC) analysis is usually consistent with that judged from the DFT calculated energy barriers, for CO2 hydrogenation to methanol over the (111) surface, our DRC analysis suggests homolytic H2 dissociation to be the rate-controlling step, which is not apparent from the DFT-calculated energy barriers. This indicates that CO2 conversion and methanol selectivity over the (111) surface can be further enhanced if homolytic H2 dissociation can be accelerated for instance by introducing transition metal dopants as already shown by some experimental observations.