Electrosynthesis of H2 O2 Promoted by π-π Interaction on a Metal-Free Carbon Catalyst.

The synthesis of hydrogen peroxide (H2 O2 ) through electrocatalytic oxygen reduction reaction is an ideal alternative to the current energy-intensive anthraquinone process, but developing cost-effective and high-efficiency electrocatalysts is still challenging. Herein, a metal-free graphitic carbon nitride/carbon nanotube (g-C3 N4 /CNT) hybrid catalyst can enhance H2 O2 production via π-π interaction is reported, achieving almost unity (97%) H2 O2 production at 0.57 V with high selectivity of over 92% across the wide potential range from 0.6 to 0 V. Other carbon materials with weak interaction with g-C3 N4 , such as acetylene black and super P, show markedly weakened H2 O2 production, indicating the importance of π-π interaction. Electron transfer kinetic analysis combined with density functional theory calculations indicates that the synergistic effect between g-C3 N4 and CNT enhances electron transfer and O2 activation between g-C3 N4 and CNT, leading to enhanced H2 O2 production performance. This work provides a complementary approach for H2 O2 production from oxygen reduction besides introducing oxygenated groups or heteroatom doping into carbon materials.

P-N Bonds-Mediated Atomic-Level Charge-Transfer Channel Fabricated between Violet Phosphorus and Carbon Nitride Favors Charge Separation and Water Splitting.

Heterostructures are widely employed in photocatalysis to promote charge separation and photocatalytic activity. However, their benefits are limited by the linkages and contact environment at the interface. Herein, violet phosphorus quantum dots (VPQDs) and graphitic carbon nitride (g-C3 N4 ) are employed as model materials to form VPQDs/g-C3 N4 heterostructures by a simple ultrasonic pulse excitation method. The heterostructure contains strong interfacial P-N bonds that mitigate interfacial charge-separation issues. P-P bond breakage occurs in the distinctive cage-like [P9] VPQD units during longitudinal disruption, thereby exposing numerous active P sites that bond with N atoms in g-C3 N4 under ultrasonic pulse excitation. The atomic-level interfacial P-N bonds of the Z-scheme VPQDs/g-C3 N4 heterostructure serve as photogenerated charge-transfer channels for improved electron-hole separation efficiency. This results in excellent photocatalytic performance with a hydrogen evolution rate of 7.70 mmol g-1  h-1 (over 9.2 and 8.5 times greater than those of pure g-C3 N4 and VPQDs, respectively) and apparent quantum yield of 11.68% at 400 nm. Using atomic-level chemical bonds to promote interfacial charge separation in phosphorene heterostructures is a feasible and effective design strategy for photocatalytic water-splitting materials.

Nanoreactor Confined and Enriched Intermediates for Electroreduction of CO2 to C2+ Products.

In the process of electroreduction of carbon dioxide (eCO2RR) to multi-carbon (C2+) products, it is imperative to enhance the concentration of key intermediate species on the catalyst surface. The utilization of micro-nano reactors to achieve confinement effects has been widely observed in various catalytic reactions, yet it has seldom been employed in eCO2RR. Here, we present a novel nanoreactor composed of stacked CuS nanosheets for eCO2RR to C2+ products. In comparison to catalyst comprising of nanosheet with open space, the C-C coupling within this confined nanospace is significantly enhanced, resulting in the increase of Faraday efficiency (FE) of C2+ products to 53 %. In situ infrared (IR) spectroscopy reveals the confinement and enrichment of key intermediate by the nanoreactor. Our research findings demonstrate that a meticulously designed nanoreactor can elevate the selectivity of C2+ products, thereby aiding in the design of eCO2RR catalysts.

Enhanced Electron Delocalization Induced by Ferromagnetic Sulfur doped C3N4 Triggers Selective H2O2 Production.

For the 2D metal-free carbon catalysts, the atomic coplanar architecture enables a large number of pz orbitals to overlap laterally, thus forming π-electron delocalization, and the delocalization degree of the central atom dominates the catalytic activity. Herein, designing sulfur-doped defect-rich graphitic carbon nitride (S-Nv-C3N4) materials as a model, we propose a strategy to promote localized electron polarization by enhancing the ferromagnetism of ultra-thin 2D carbon nitride nanosheets. The introduction of sulfur (S) further promotes localized ferromagnetic coupling, thereby inducing long-range ferromagnetic ordering and accelerating the electron interface transport. Meanwhile, the hybridization of sulfur atoms breaks the symmetry and integrity of the unit structure, promotes electron enrichment and stimulating electron delocalization at the active site. This optimization enhances the *OOH desorption, providing a favorable kinetic pathway for the production of hydrogen peroxide (H2O2). Consequently, S-Nv-C3N4 exhibits high selectivity (>95 %) and achieves a superb H2O2 production rate, approaching 4374.8 ppm during continuous electrolysis over 300 hour. According to theoretical calculation and in situ spectroscopy, the ortho-S configuration can provide ferromagnetic perturbation in carbon active centers, leading to the electron delocalization, which optimizes the OOH* adsorption during the catalytic process.

Confirming High-Valent Iron as Highly Active Species of Water Oxidation on the Fe, V-Coupled Bimetallic Electrocatalyst: In Situ Analysis of X-ray Absorption and Mössbauer Spectroscopy.

Iron (Fe)-based bimetallic oxides/hydroxides have been widely investigated for promising alkaline electrochemical oxygen evolution reactions (OERs), but it still remains argumentative whether Fe3+ or Fe4+ intermediates are highly active for efficient OER. Here, we rationally designed and prepared one Fe, V-based bimetallic composite nanosheet by employing the OER-inert V element as a promoter to completely avoid the argument of real active metals and using our recently developed one-dimensional conductive nickel phosphide (NP) as a support. The as-obtained hierarchical nanocomposite (denoted as FeVOx/NP) was evaluated as a model catalyst to gain insight into the iron-based species as highly active OER sites by performing in situ X-ray absorption spectroscopy and 57Fe Mössbauer spectroscopy measurements. It was found that the high-valent Fe4+ species can only be detected during the OER process of the FeVOx/NP nanocomposite instead of the iron counterpart itself. Together with the fact that the OER activities of both the vanadium and iron counterparts are by far worse than that of the FeVOx/NP composite, we can confirm that the high-valent Fe4+ formed are the highly active species for efficient OER. As demonstrated by density functional theory simulations, the composite of Fe and V metals is proposed to cause a decreased Gibbs free energy as well as theoretical overpotential of water oxidation with respect to its counterparts, as is responsible for its excellent OER performance with extremely low OER overpotential (290 mV at 500 mA cm-2) and extraordinary stability (1000 h at 100 mA cm-2).

Transport of neonicotinoid insecticides in a wetland ecosystem: Has the cultivation of different crops become the major sources?

Extensive application of neonicotinoid insecticides (NNIs) in agricultural production has resulted in widespread contamination of multiple environmental media. To investigate the occurrence and fate of NNIs in the largest marsh distribution area in Northeast China, an integrated ecosystem covering farmlands, rivers, and marshes, referred to as the farmland-river-marsh continuum in this study, was chosen for soil, water, and sediment sampling. Five NNIs were detected, with imidacloprid (IMI), thiamethoxam (THM), and clothianidin (CLO) being the most frequently detected ones in different samples. Concentrations of target NNIs in soil, surface water, and sediment samples were 2.23-136 ng/g dry weight (dw), 3.20-51.7 ng/L, and 1.53-8.40 ng/g dw, respectively. In soils, NNIs were detected more often and at higher concentrations in upland fields, while the concentration of NNIs in the soybean-growing soils (71.5 ng/g dw) was significantly higher than in the rice-growing soils (18.5 ng/g dw) (p < 0.05). Total concentration of NNIs in surface water was lower in the Qixing River channel than inside the marsh, while that in sediments showed an opposite trend. Total migration mass of IMI from approximately 157,000 ha of farmland soil by surface runoff was estimated to be 2636-3402 kg from the application time to the sampling period. The storage of NNIs in sediments was estimated to range from 45.9 to 252 ng/cm2. The estimated environmental risks, calculated as the risk quotients (RQs), revealed low risks to aquatic organisms (RQs <0.1) from the residual concentrations of NNIs in water.

Insight into the Key Restriction of BiVO4 Photoanodes Prepared by Pyrolysis Method for Scalable Preparation.

Bismuth Vanadate (BiVO4 ) photoanode has been popularly investigated for promising solar water oxidation, but its intrinsic performance has been greatly retarded by the direct pyrolysis method. Here we insight the key restriction of BiVO4 prepared by metal-organic decomposition (MOD) method. It is found that the evaporation of vanadium during the pyrolysis tends to cause a substantial phase impurity, and the unexpected few tetragonal phase inhibits the charge separation evidently. Consequently, suitably excessive vanadium precursor was adopted to eliminate the phase impurity, based on which the obtained intrinsic BiVO4 photoanode could exhibit photocurrent density of 4.2 mA cm-2 at 1.23 VRHE under AM 1.5 G irradiation, as comparable to the one fabricated by the currently popular two-step electrodeposition method. Furthermore, the excellent performance can be maintained on the enlarged photoanode (25 cm2 ), demonstrating the advantage of MOD method in scalable preparation. Our work provides new insight and highlights the glorious future of MOD method for the design of scale-up efficient BiVO4 photoanode.

Layered ß-ZrNBr Nitro-Halide as Multifunctional Photocatalyst for Water Splitting and CO2 Reduction.

Developing mixed-anion semiconductors for solar fuel production has inspired extensive interest, but the nitrohalide-based photocatalyst is still in shortage. Here we report a layered nitro-halide ß-ZrNBr with a narrow band gap of ca. 2.3 eV and low defect density to exhibit multifunctionalities for photocatalytic water reduction, water oxidation and CO2 reduction under visible-light irradiation. As confirmed by the results of electron paramagnetic resonance (EPR) and density functional theory (DFT) calculations, the formation of anion vacancies in the nitro-halide photocatalyst was inhibited due to its relatively high formation energy. Furthermore, performance of ß-ZrNBr can be effectively promoted by a simple exfoliation into nanosheets to shorten the carrier transfer distance as well as to promote charge separation. Our work extends the territory of functional photocatalysts into the nitro-halide, which opens a new avenue for fabricating efficient artificial photosynthesis.

Single Atom Bi Decorated Copper Alloy Enables C-C Coupling for Electrocatalytic Reduction of CO2 into C2+ Products.

Single atom alloy (SAA) catalysts have been recently explored for promotion of various heterogeneous catalysis, but it remains unexplored for selective electrocatalytic reduction of carbon dioxide (CO2 ) into multi-carbon (C2+ ) products involving C-C coupling. Herein we report a single-atomic Bi decorated Cu alloy (denoted as BiCu-SAA) electrocatalyst that could effectively modulate selectivity of CO2 reduction into C2+ products instead of previous C1 ones. The BiCu-SAA catalyst exhibits remarkably superior selectivity of C2+ products with optimal Faradaic efficiency (FE) of 73.4 % compared to the pure copper nanoparticle or Bi nanoparticles-decorated Cu nanocomposites, and its structure and performance can be well maintained at current density of 400 mA cm-2 under the flow cell system. Based on our in situ characterizations and density functional theory calculations, the BiCu-SAA is found to favor the activation of CO2 and subsequent C-C coupling during the electrocatalytic reaction, as should be responsible for its extraordinary C2+ selectivity.

Water-Stable Nickel Metal-Organic Framework Nanobelts for Cocatalyst-Free Photocatalytic Water Splitting to Produce Hydrogen.

Development of water-stable metal-organic frameworks (MOFs) for promising visible-light-driven photocatalytic water splitting is highly desirable but still challenging. Here we report a novel p-type nickel-based MOF single crystal (Ni-TBAPy-SC) and its exfoliated nanobelts (Ni-TBAPy-NB) that can bear a wide range of pH environment in aqueous solution. Both experimental and theoretical results indicate a feasible electron transfer from the H4TBAPy ligand (light-harvesting center) to the Ni-O cluster node (catalytic center), on which water splitting to produce hydrogen can be efficiently driven free of cocatalyst. Compared to the single crystal, the exfoliated two-dimensional (2D) nanobelts show more efficient charge separation due to its shortened charge transfer distance and remarkably enhanced active surface areas, resulting in 164 times of promoted water reduction activity. The optimal H2 evolution rate on the nanobelt reaches 98 µmol h-1 (ca. 5 mmol h-1 g-1) showing benchmarked apparent quantum efficiency (AQE) of 8.0% at 420 nm among water-stable MOFs photocatalysts.

Synthesis of Nickel Nitride-Based 1D/0D Heterostructure via a Morphology-Inherited Nitridation Strategy for Efficient Electrocatalytic Hydrogen Evolution.

The fabrication of heterostructures has inspired extensive interest in promoting the performance of solar cells or solar fuel production, but it is still challenging for nitrides to prepare structurally ordered heterostructures. Herein, one nickel nitride-based heterostructure composed of 1D Ni0.2 Mo0.8 N nanorods and 0D Ni3 N nanoparticles (denoted as NiMoN/NiN) is reported to exhibit significantly promoted hydrogen evolution reaction performance in both alkaline and neutral media. In particular, the optimal overpotential of the NiMoN/NiN sample at 10 mA cm-2 in 1 m KOH is 49 mV. The successful fabrication of 1D/0D heterostructures is mainly ascribed to morphology-inherited nitridation of 1D oxide precursor (denoted as NiMoO-NRs) in situ grown on Ni foam surface, and attributed to strong Lewis acid-base interaction that renders the Ni2+ ions emitted from the oxide precursor to well coordinate with NH3 for the formation of Ni3 N nanoparticles during the nitridation process. It is theoretically and experimentally demonstrated that the special 1D/0D heterostructure provides tandem active phases Ni0.2 Mo0.8 N and Ni3 N for synergistic promotion in lowering the activation energy of H2 O dissociation and optimizing the adsorption energy of H, respectively. This work may open a new avenue for developing highly active tandem electrocatalysts for promising renewable energy conversion.

Effective Charge Carrier Utilization of BiVO4 for Solar Overall Water Splitting.

Solar energy-driven overall water splitting (OWS) is an attractive way for generating clean and renewable green hydrogen. One key challenge is the construction of OWS systems with high solar energy conversion efficiencies, in which how to manipulate photoexcited charge carriers to efficiently participate in the reaction is the top priority. In recent years, bismuth vanadate (BiVO4 ) has emerged as one of the most promising materials for photo(electro)catalytic OWS and considerable progress has been achieved. In this review, recent advances of BiVO4 -constituted OWS systems in both photoelectrocatalytic and photocatalytic approaches are presented in a mainline of effective charge carrier utilization. Various strategies for improved charge carrier utilization, including band structure engineering, improving charge separation, reducing charge recombination, and accelerating reaction kinetics, are summarized and analyzed in detail. Finally, perspective and outlook on further exploring the application potential of BiVO4 are proposed.

Main Descriptors To Correlate Structures with the Performances of Electrocatalysts.

Traditional trial and error approaches to search for hydrogen/oxygen redox catalysts with high activity and stability are typically tedious and inefficient. There is an urgent need to identify the most important parameters that determine the catalytic performance and so enable the development of design strategies for catalysts. In the past decades, several descriptors have been developed to unravel structure-performance relationships. This Minireview summarizes reactivity descriptors in electrocatalysis including adsorption energy descriptors involving reaction intermediates, electronic descriptors represented by a d-band center, structural descriptors, and universal descriptors, and discusses their merits/limitations. Understanding the trends in electrocatalytic performance and predicting promising catalytic materials using reactivity descriptors should enable the rational construction of catalysts. Artificial intelligence and machine learning have also been adopted to discover new and advanced descriptors. Finally, linear scaling relationships are analyzed and several strategies proposed to circumvent the established scaling relationships and overcome the constraints imposed on the catalytic performance.

Pre-ischemic renal lavage protects against renal ischemia-reperfusion injury by attenuation of local and systemic inflammatory responses.

Postischemic acute kidney injury (AKI) is a common clinical complication and often fatal, with no effective treatment available. Little is known about the role of leukocytes trapped in renal vessels during ischemia-reperfusion injury (IRI) in the postischemic AKI. We designed a new animal model in rats with preforming renal artery lavage prior to IRI to investigate the effect of diminishing the residual circulating leukocytes on kidney damage and inflammation. Moreover, the functional changes of macrophages in hypoxia reoxygenation condition were also analyzed. We found pre-ischemic renal lavage significantly decreased the serum creatinine and blood urea nitrogen levels, and downregulated the mRNA and protein expressions in kidneys and urinary secretion of kidney injury molecule-1 of rats after IRI. The renal pathological damage caused by IRI was also ameliorated by pre-ischemic renal lavage, as evidenced by fewer cast formation, diminished morphological signs of AKI in the tissue at 24 hours after IRI. Pre-ischemic renal lavage reduced the numbers of infiltrating CD68+ macrophages and MPO+ neutrophils. The mRNA expression of pro-inflammatory mediator in IRI kidneys and the levels of pro-inflammatory cytokines in circulatory system and urine were also reduced due to pre-ischemic lavage. Compared with nontreated rats with IRI, pre-ischemic renal lavage significantly reduced the phosphorylation levels of ERK and p65 subunit of NF-κB in the kidney after IRI. In addition, we found hypoxia/reoxygenation could promote the expression of pro-inflammatory mediators and inhibit the expression of anti-inflammatory factors by regulating ERK/NF-κB signaling pathway. Thus, pre-ischemic renal lavage could clearly reduce the renal damage after IRI by attenuating inflammation, and macrophages trapped in renal vessels during IRI could be important pathogenic factors driving tissue injury.

Water-Stable Cobalt-Based MOF for Water Oxidation in Neutral Aqueous Solution: A Case of Mimicking the Photosystem II.

Inspired by the highly efficient water oxidation of Mn4CaO5 in natural photosynthesis, development of novel artificial water oxidation catalysts (WOCs) with structure and function mimicked has inspired extensive interests. A novel 3D cobalt-based MOF (GXY-L8-Co) was synthesized for promising artificial water oxidation by employing the Co4O4 quasi-cubane motifs with a similar structure as the Mn4CaO5 as the core. The GXY-L8-Co not only shows good chemical stability in common organic solvents or water for up to 10 days but also exhibits oxygen evolution performance. It has been demonstrated that the uniform distribution of Co4O4 catalytic active sites confined in the MOF framework should be responsible for the good robustness and catalytic performance.

ThMnPnN (Pn = P, As): Synthesis, Structure, and Chemical Pressure Effects.

Mn-based ZrCuSiAs-type pnictides ThMnPnN (Pn = P, As) containing PbO-type Th2N2 layers were synthesized. The crystal and magnetic structures are determined using X-ray and neutron powder diffraction. While neutron diffraction indicates a C-type antiferromagnetic state at 300 K, the temperature dependence of the magnetic susceptibility shows cusps at 36 and 52 K respectively for ThMnPN and ThMnAsN. The susceptibility cusps are ascribed to a spontaneous antiferromagnetic-to-antiferromagnetic transition for Mn2+ moments, which is observed for the first time in Mn-based ZrCuSiAs-type compounds. In addition, measurements of the resistivity and specific heat suggest an abnormal increase in the density of states at the Fermi energy. The result is discussed in terms of the internal chemical pressure effect.

Thermal stability and irradiation response of nanocrystalline CoCrCuFeNi high-entropy alloy.

Grain growth and phase stability of a nanocrystalline face-centered cubic (fcc) Ni0.2Fe0.2Co0.2Cr0.2Cu0.2 high-entropy alloy (HEA), either thermally- or irradiation-induced, are investigated through in situ and post-irradiation transmission electron microscopy (TEM) characterization. Synchrotron and lab x-ray diffraction measurements are carried out to determine the microstructural evolution and phase stability with improved statistics. Under in situ TEM observation, the fcc structure is stable at 300 °C with a small amount of grain growth from 15.8 to ∼20 nm being observed after 1800 s. At 500 °C, however, some abnormal growth activities are observed after 1400 s, and secondary phases are formed. Under 3 MeV Ni room temperature ion irradiation up to an extreme dose of nearly 600 displacements per atom, the fcc phase is stable and the average grain size increases from 15.6 to 25.2 nm. Grain growth mechanisms driven by grain rotation, grain boundary curvature, and disorder are discussed.

Multicenter surveillance study of surgical site infection and its risk factors in radical resection of colon or rectal carcinoma.

BACKGROUND: Colorectal surgery is associated with high rates of surgical site infection (SSI). We investigated SSI in radical resection of colon or rectal carcinoma and its epidemiological distribution in 26 hospitals in China. METHODS: We conducted prospective surveillance of patients who underwent radical resection of colon or rectal carcinoma in 26 selected hospitals from January 2015 to June 2016.An information system monitored all of the surgical inpatients. Infection control professionals observed the inpatients with suspected SSI who had been screened by the system at the bedside. The infection status of the incisions was followed up by telephone 1 month after the operation. RESULTS: In total, 5729 patients were enrolled for the two operations; SSIs occurred in 206 patients, and the infection rate was 3.60%. The incidence of SSI after radical resection of rectal carcinoma (5.12%; 119/2323) was 2.1 times higher than that after radical resection of colon carcinoma (2.55%; 87/3406) (P < 0.0001). Additionally, in the colon versus rectal groups, the rate of superficial incisional SSI was 0.94% versus 2.28% (P < 0.0001), the rate of deep incisional SSI was 0.56% versus 1.11% (P = 0.018), and the rate of organ space SSI was 1.06% versus 1.72% (P = 0.031), respectively. The most common pathogens causing SSIs after radical resection of colon carcinoma were Escherichia coli (21/38) and Pseudomonas aeruginosa (5/38). Escherichia coli (24/65) and Enterococcus spp. (14/65) were the two most common pathogens in the rectal group. The multivariate logistic regression analysis showed that only the operating time and number of hospital beds were common independent risk factors for SSIs after the two types of surgery. CONCLUSION: This multicenter study showed that there were significant differences in the incidence of SSIs, three types of SSIs, and some risk factors between radical resection of colon carcinoma and rectal carcinoma.

Trophic transfer of cyclic methyl siloxanes in the marine food web in the Bohai Sea, China.

Trophic transfer of cyclic methyl siloxanes (CMS) in aquatic ecosystems is an important criterion for assessing its environmental risks. This study researched the trophic transfer of four CMS (octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), dodecamethylcyclohexasiloxane (D6), and tetradecamethylcycloheptasiloxane (D7)) in marine food web from zooplankton up to seabirds in the Chinese Bohai Sea. In the zooplankton-invertebrate-fish-seabird based food web, the significant trophic magnifications were found for D4 to D6 (D4: R2 = 0.040, p < 0.05, D5: R2 = 0.26, p < 0.0001, D6: R2 = 0.071, p < 0.001), and the significant trophic dilution was found for D7 (R2 = 0.026 and p < 0.05). The trophic magnification factors (TMF) for D4 to D7 were 1.7 (95% confidence interval: 1.1-2.6), 3.5 (2.5-5.0), 1.8 (1.3-2.6), and 0.63 (95% CI: 0.40-0.99) respectively. In the zooplankton-invertebrate-fish based food web, both significant trophic magnification for D5 (R2 = 0.16, p < 0.0001, TMF = 3.0) and significant trophic dilution for D7 (R2 = 0.073, p < 0.01, TMF = 0.4) were found, but for D4 and D6, the trophic magnifications were not significant (D4: R2 = 0.010, p = 0.23, D6: R2 = 0.010, p = 0.23). The trophic transfer of the legacy contaminant BDE-47 and BDE-99 were also conducted as the benchmark chemicals and significant positive correlation was found. As far as we know, this is the first research on the trophic transfer of CMS in the zooplankton-invertebrate-fish-bird food chain which provided new insight of these compounds in the area.

A2TiO5 (A = Dy, Gd, Er, Yb) at High Pressure.

The structural evolution of lanthanide A2TiO5 (A = Dy, Gd, Yb, Er) at high pressure is investigated using synchrotron X-ray diffraction. The effects of A-site cation size and of the initial structure are systematically examined by varying the composition of the isostructural lanthanide titanates and the structure of dysprosium titanate polymorphs (orthorhombic, hexagonal, and cubic), respectively. All samples undergo irreversible high-pressure phase transformations, but with different onset pressures depending on the initial structure. While each individual phase exhibits different phase transformation histories, all samples commonly experience a sluggish transformation to a defect cotunnite-like (Pnma) phase for a certain pressure range. Orthorhombic Dy2TiO5 and Gd2TiO5 form P21am at pressures below 9 GPa and Pnma above 13 GPa. Pyrochlore-type Dy2TiO5 and Er2TiO5 as well as defect-fluorite-type Yb2TiO5 form Pnma at ∼21 GPa, followed by Im3̅m. Hexagonal Dy2TiO5 forms Pnma directly, although a small amount of remnants of hexagonal Dy2TiO5 is observed even at the highest pressure (∼55 GPa) reached, indicating kinetic limitations in the hexagonal Dy2TiO5 phase transformations at high pressure. Decompression of these materials leads to different metastable phases. Most interestingly, a high-pressure cubic X-type phase (Im3̅m) is confirmed using high-resolution transmission electron microscopy on recovered pyrochlore-type Er2TiO5. The kinetic constraints on this metastable phase yield a mixture of both the X-type phase and amorphous domains upon pressure release. This is the first observation of an X-type phase for an A2BO5 composition at high pressure.