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To study the deformation failure and damage evolution law of weathered granite (WG) under different confining pressures, triaxial compression simultaneous acoustic emission (AE) tests were conducted on WG, and the mechanical and AE parameter characteristics of WG were obtained. It is shown that with the increase of confining pressure, the strength and modulus of elasticity of WG increase, and the failure pattern evolves from splitting failure to shear failure. Using the Mohr-Coulomb criterion, the cohesion c of WG is calculated to be 7.03 MPa, and the angle of internal friction φ is 61.95°. Analysing the AE peak frequency and energy at the characteristic points of the differential stress-axial strain curves, it is evident that the confining pressure limits crack evolution. The fractal characteristics of the WG AE ringing counts at each confining pressure are good, and the correlations between their ln r-ln C(r) curves and the fitted curves are all above 0.90. The WG at each confining pressure showed an increasing growth rate in the values of the damage variables and a rapid and substantial decrease in the fractal dimension before failure occurred. The study's results can provide a theoretical basis for the stability analysis of the WG surrounding rock. [ABSTRACT FROM AUTHOR]

Sustaining the steady state for highly active non‐stoichiometric iridium (Ir)‐based oxide (IrOx) at low Ir loading remains challenging primarily due to the continuous oxidation and sequent dissolution of Ir active sites during the oxygen evolution reaction (OER). In this context, a new iridium–cerium (Ce) substitution solid solution oxide (SSO) has been developed, featuring uniformly dispersed Ir atoms within Ce dioxide (CeO2) matrix as electron buffer, which delivers remarkable acidic OER catalytic activity and enhanced stability. The electron‐buffering capacity of CeO2 facilitates the charge transfer toward Ir atoms, leading to abundant active low‐valence Ir sites and effectively prevent their oxidation and dissolution. As a result, Ir─Ce SSO demonstrates an overpotential of merely 238 mV@10 mA cm−2. Proton exchange membrane water electrolyzer employing Ir─Ce SSO at a low Ir loading of 396 µgIr cm−2 operates consistently for over 100 h@500 mA cm−2. Density functional theory (DFT) calculations corroborate that the electron‐buffering effect of CeO2 enriches the density of IrIII and substantially increases the dissolution energy barrier of Ir atoms. This study presents a viable approach to addressing the issues of instability and low efficiency in Ir‐based OER electrocatalysts for acidic water electrolysis. [ABSTRACT FROM AUTHOR]

To clarify the influence mechanism of initial defects on the internal crack evolution law and damage destruction of cement superfine tailings backfill(CSTB), uniaxial compression and simultaneous acoustic emission (AE) tests were carried out on CSTB with different degrees of internal initial defects constructed by doping with different contents of doping agent(DA), and the AE b-value, amplitude fractal dimensional time series characteristics and three-dimensional distribution law of AE events of CSTBs were analyzed in this paper. The research shows that the doping of DA caused the fluctuation and jump of the CSTB b-value to be significantly enhanced, and the b-value showed two jumps in the loading process. The fractal characteristics of CSTB with different DA doping are better, and the fractal dimension D-value and b-value both show a rapid decreasing trend in the preparation process of the specimen for the occurrence of overall unstable failure. The admixture of DA increases the number of initial defects and non-homogeneity within the CSTB, making the generation of 3D localization points of AE events somewhat random. The results of the study can help to better analyze the unstable failure process of the backfill in the mine hollow area and carry out the corresponding support work. [ABSTRACT FROM AUTHOR]

Weathering of granite leads to weakening of its crushing and mechanical properties, as well as changes in mineral composition. In order to investigate the correlation between the effects of weathering on granite and the characterization of the pore structure at the micro- and fine-scale, in this paper the pore structure of weathered granite is tested by the NMR technique. The pore distribution characteristics of weathered granite were explored in conjunction with T2 spectral relaxation time and fractal theory. The microstructure of weathering-prone granite was monitored using scanning electron microscopy equipment. The results show that the pores can be classified into the three categories of small, medium and large pores based on their pore size distribution characteristics. Weathered granite has fractal features in the mesopores and macropores. Compared with unweathered granite, weathered granite has significantly more small pore throats and fewer medium and large pore throats, which expand into microfissures and micropores under conditions of weathering. The microstructure of weathered granite is mainly flaky and shell-like, with good connectivity, resulting in the poor overall structure of weathered granite. [ABSTRACT FROM AUTHOR]

To reduce the economic cost of backfilling a mine, layers of cemented materials with different ash sand ratios are often used to backfill the void. In this study, we explored the damage evolution mechanism from the energy consumption point of view for backfill and rock combination with different ash sand ratios, and introduced the strength dissipation rate, damage value parameter and elastic strain energy rate to achieve the definition of damage in the specimens, as well as the characterization of the energy accumulation effect. In addition, the layered backfilling of the assemblage was simulated using FLAC3D software. The results show that: (1) the elastic strain energy rate can reflect the accumulation ability of the strain energy of the specimen; the larger the strain energy rate, the stronger the accumulation ability; (2) the damage evolution of the backfill–backfill combination is divided into stages: initial damage repair stage, damage stable development stage, damage accelerated development stage and residual damage stage; and (3) the top layer with an ash/sand ratio of 1:4, the middle layer with an ash/sand ratio of 1:8 and the bottom layer with an ash/sand ratio of 1:10 is the optimal backfilling scheme. This study can provide a theoretical reference for the backfilling of a hollow area. [ABSTRACT FROM AUTHOR]

Transition‐metal atomic site catalysts (ASCs) are a new class of catalytic system for CO2 electroreduction, however, their practical application is greatly hindered by the challenge that it's still difficult for them to simultaneously achieve industrial‐level current density and high selectivity. Herein a new strategy is reported for hundreds of gram‐scale and low‐cost production of Ni‐ASCs on 3D porous nanocarbon with high‐loading NiN3 sites for greatly boosting the electroreduction of CO2 to CO with both industrial‐level current density and high selectivity. It is discovered that although Ni‐ASCs with high‐loading (Ni‐ASCs/4.3 wt.%) and low‐loading (Ni‐ASCs/0.8 wt.%) both show above 95% Faradic efficiency for CO (FECO) under a wide potential range in H‐cell, in flow cell, Ni‐ASCs/0.8 wt.% can only achieve FECO of 43.6% at a current density of 343.9 mA cm−2, significantly lower than those (95.1%, 533.3 mA cm−2) of Ni‐ASCs/4.3 wt.% under same potential, first revealing the important role of high‐loadings of single atom sites in promoting the high‐selectivity electrolysis at industrial‐level current density. Most importantly, it is demonstrated that Ni‐ASCs/4.3 wt.%‐based membrane electrode assembly (MEA) exhibits outstanding durability at industrial‐level current density of 360.0 mA cm−2, which is one of the best performances for the realistic electroreduction of CO2 to CO in the reported ASCs‐based MEA systems. [ABSTRACT FROM AUTHOR]

As the most well-known electrocatalyst for cathodic hydrogen evolution in water splitting electrolyzers, platinum is unfortunately inefficient for anodic oxygen evolution due to its over-binding with oxygen species and excessive dissolution in oxidative environment. Herein we show that single Pt atoms dispersed in cobalt hydrogen phosphate with an unique Pt(OH)(O3)/Co(P) coordination can achieve remarkable catalytic activity and stability for oxygen evolution. The catalyst yields a high turnover frequency (35.1 ± 5.2 s−1) and mass activity (69.5 ± 10.3 A mg−1) at an overpotential of 300 mV and excellent stability. Mechanistic studies elucidate that the superior catalytic performance of isolated Pt atoms herein stems from optimal binding energies of oxygen intermediate and also their strong electronic coupling with neighboring Co atoms that suppresses the formation of soluble Ptx>4 species. Alkaline water electrolyzers assembled with an ultralow Pt loading realizes an industrial-level current density of 1 A cm−2 at 1.8 volts with a high durability. Platinum is the most active catalyst for cathodic hydrogen evolution, however it is inefficient for anodic oxygen evolution. Here, authors examine Pt single sites in cobalt hydrogen phosphate as oxygen evolution catalysts in water splitting electrolyzers. [ABSTRACT FROM AUTHOR]

Incorporation of fibers in the cemented body material can obviously improve its mechanical properties. Digital image correlation (DIC) and acoustic emission (AE) techniques were used to monitor the “optical-acoustic” response in uniaxial compression failure progress of the fiber-free and glass fiber-reinforced cemented bodies, and the response characteristics of the two methods in the stability monitoring of the cemented body as a support structure were discussed. The results show that the glass fiber-reinforced cemented body showed a failure to the internal structure after the peak strength, but the specimen remained intact without spalling and still maintained a long ductile deformation. The transverse displacement changes curve of the fiber-free cemented body appeared a “positive-negative turning point”. The transverse displacement of the glass fiber-reinforced cemented body is negatively correlated with the DIC time. The full-field strain information obtained by the DIC technique can be used to quantify the degree of damage on the surface of the cemented bodies, and the AE ringing count and energy signal response are more sensitive to the internal friction and impact of the cemented bodies. The results of the study can provide a reference for determining the stability monitoring method of the cemented body as a support structure. [ABSTRACT FROM AUTHOR]

Although dispersing Pt atomic clusters (ACs) on a conducting support is a promising way to minimize the Pt amount required in hydrogen evolution reaction (HER), the catalytic mass activity and durability of Pt ACs are often unsatisfactory for alkaline HER due to their unfavorable water dissociation and challenges in stabilizing them against agglomeration and detachment. Herein, we report a class of single-atom Cr-N 4 sites with high oxophilicity interfaced with Pt ACs on mesoporous carbon for achieving a highly active and stable alkaline HER in an anion-exchange-membrane water electrolyzer (AEMWE). The as-made catalyst achieves the highest reported Pt mass activity (37.6 times higher than commercial Pt/C) and outstanding operational stability. Experimental and theoretical studies elucidate that the formation of a unique Pt-Cr quasi-covalent bonding interaction at the interface of Cr-N 4 sites and Pt ACs effectively suppresses the migration and thermal vibration of Pt atoms to stabilize Pt ACs and contributes to the greatly enhanced catalytic stability. Moreover, oxophilic Cr-N 4 sites adjacent to Pt ACs with favorable adsorption of hydroxyl species facilitate nearly barrierless water dissociation and thus enhance the HER activity. An AEMWE using this catalyst (with only 50 μg Pt cm -2 ) can operate stably at an industrial-level current density of 500 mA cm -2 at 1.8 V for >100 h with a small degradation rate of 90 μV h -1 .

The electrochemical carbon dioxide reduction reaction (CO 2 RR) to formate is of great interest in the field of electrochemical energy. Cu-based material is an appealing electrocatalyst for the CO 2 RR. However, retaining Cu 2+ under the high cathodic potential of CO 2 RR remains a great challenge, leading to low electrocatalytic selectivity, activity, and stability. Herein, inspired by corrosion science, a sacrificial protection strategy to stabilize interfacial crystalline CuO through embedding of active amorphous SnO 2 (c-CuO/a-SnO 2 ) is reported, which greatly boosts the electrocatalytic sensitivity, activity, and stability for CO 2 RR to formate. The as-made hybrid catalyst can achieve superior high selectivity for CO 2 RR to formate with a remarkable Faradaic efficiency (FE) of 96.7%, and a superhigh current density of over 1 A cm -2 that far outperforms industrial benchmarks (FE > 90%, current density > 300 mA cm -2 ). In situ X-ray absorption spectroscopy (XAS) and X-ray diffractionexperimental and theoretical calculation results reveal that the broadened s-orbital in interfacial a-SnO 2 offers the lower orbital for extra electrons than Cu 2+ , which can effectively retain nearby Cu 2+ , and the high active interface significantly lowers the energy barrier of the limited step ( * CO 2 → * HCOO) and enhances the selectivity and activity for CO 2 RR to formate., (© 2023 Wiley-VCH GmbH.)

Designing efficient and durable bifunctional catalysts for 5-hydroxymethylfurfural (HMF) oxidation reaction (HMFOR) and hydrogen evolution reaction (HER) is desirable for the co-production of biomass-upgraded chemicals and sustainable hydrogen, which is limited by the competitive adsorption of hydroxyl species (OH ads ) and HMF molecules. Here, we report a class of Rh-O 5 /Ni(Fe) atomic site on nanoporous mesh-type layered double hydroxides with atomic-scale cooperative adsorption centers for highly active and stable alkaline HMFOR and HER catalysis. A low cell voltage of 1.48 V is required to achieve 100 mA cm -2 in an integrated electrolysis system along with excellent stability (>100 h). Operando infrared and X-ray absorption spectroscopic probes unveil that HMF molecules are selectively adsorbed and activated over the single-atom Rh sites and oxidized by in situ-formed electrophilic OH ads species on neighboring Ni sites. Theoretical studies further demonstrate that the strong d-d orbital coupling interactions between atomic-level Rh and surrounding Ni atoms in the special Rh-O 5 /Ni(Fe) structure can greatly facilitate surface electronic exchange-and-transfer capabilities with the adsorbates (OH ads and HMF molecules) and intermediates for efficient HMFOR and HER. We also reveal that the Fe sites in Rh-O 5 /Ni(Fe) structure can promote the electrocatalytic stability of the catalyst. Our findings provide new insights into catalyst design for complex reactions involving competitive adsorptions of multiple intermediates.

Aqueous zinc-ion batteries (AZIBs) are attractive energy storage devices that benefit from improved safety and negligible environmental impact. The V 2 O 5 -based cathodes are highly promising, but the dissolution of vanadium is one of the major challenges in realizing their stable performance in AZIBs. Herein, we design a Ti 3 C 2 T x MXene layer on the surface of V 2 O 5 nanoplates (VPMX) through a van der Waals self-assembly approach for suppressing vanadium dissolution during an electrochemical process for greatly boosting the zinc-ion storage performance. Unlike conventional V 2 O 5 /C composites, we demonstrate that the VPMX hybrids offer three distinguishable features for achieving high-performance AZIBs: (i) the MXene layer on cathode surface maintains structural integrity and suppresses V dissolution; (ii) the heterointerface between V 2 O 5 and MXene enables improved host electrochemical kinetics; (iii) reduced electrostatic repulsion exists among host layers owing to the lubricating water molecules in the VPMX cathode, facilitating interfacial Zn 2+ diffusion. As a result, the as-made VPMX cathode shows a long-term cycling stability over 5000 cycles, surpassing other reported V 2 O 5 -based materials. Especially, we find that the heterointerface between V 2 O 5 and MXene and lubricated water molecules in the host can achieve an enhanced rate capability (243.6 mAh g -1 at 5.0 A g -1 ) for AZIBs.