Rational regulation of electrochemical reconfiguration and exploration of activity origin are important foundations for realizing the optimization of electrocatalyst activity, but rather challenging. Herein, we potentially develop a rapid complete reconfiguration strategy for the heterostructures of CoC2O4 coated by MXene nanosheets (CoC2O4@MXene) during the hydrogen evolution reaction (HER) process. The self-assembled CoC2O4@MXene nanotubular structure has high electronic accessibility and abundant electrolyte diffusion channels, which favor the rapid complete reconfiguration. Such rapid reconfiguration creates new actual catalytic active species of Co(OH)2 transformed from CoC2O4, which is coupled with MXene to facilitate charge transfer and decrease the free energy of the Volmer step toward fast HER kinetics. The reconfigured components require low overpotentials of 28 and 216 mV at 10 and 1000 mA cm−2 in alkaline conditions and decent activity and stability in natural seawater. This work gives new insights for understanding the actual active species formation during HER and opens up a new way toward high-performance electrocatalysts.

We systematically investigate the distance that dynamically propagating earthquake ruptures could jump across step overs in strike‐slip faults set in a homogeneous half‐space. The following factors are found to have major effects on the critical jump distance: the dimensionless effective shear stress, the initial normal stress, the Earth's free surface, and the accelerating length of the rupture front on the main fault prior to a jump. An important finding in this study is that the critical jump distance for extensional step overs could exceed 10 km under certain conditions, while ruptures on compressional step overs under the same conditions could only jump 6 km fault step overs. This may provide a physical explanation for some geological observations of over 10 km jump distance in natural earthquake. The critical jump distance usually increases as the dimensionless effective shear stress increases. Without the free surface effect, the critical jump distance for step overs could only reach up to 6 km, which is very close to the 5 km given by the classic 2‐D simulations.

Few studies have focused on the supershear transition mechanism induced by fault step overs, although seismic observations suggest that rupture speed transitions occur at geometrical complexities on faults. Based on dynamic rupture simulations on fault systems with step overs in a 3‐D full space where the initial stresses preclude a supershear transition on a single buried fault according to the Burridge‐Andrews mechanism, we show that rupture speeds can transit from subshear on the primary fault to supershear on the secondary fault. The low normal stress zone and the high shear stress zone beyond the fault step, which radiate from the end of the primary fault if its rupture arrest is sudden, determine the supershear rupture occurrence on the secondary fault. However, a low shear stress zone traveling at the shear wave speed is also radiated, making the rupture speed return to subshear in most cases. Sustained supershear ruptures are also possible on compressional step overs under certain conditions. Self‐arresting ruptures are observed in the overlap area on the secondary fault. In a half‐space model where supershear rupture is induced by the free surface on the primary fault, the rupture speed on the secondary fault rapidly transits to subshear near the fault step if its width exceeds a critical value.

While prior numerical simulations indicate that the Earth's free surface can induce supershear propagation on strike‐slip faults, copious observations of strike‐slip earthquakes have produced only a few instances of such supershear rupture. Our dynamic rupture simulations with varying initial normal stresses and fault strengths show that free‐surface‐induced supershear rupture on strike‐slip faults may return to sub‐Rayleigh speed as the rupture progresses. Such a phenomenon is defined as unsustained free‐surface‐induced supershear rupture, indicating that a rupture on a strike‐slip fault, even if it encounters the free surface, may not generate supershear rupture that is sustained long enough to be observable. The shape of the rupture front contour on the fault may also lead to a false impression about the rupture velocity, since the daughter crack may also propagate at sub‐Rayleigh speed, with near‐field fault‐perpendicular ground motion. Shallower hypocenter depths increase the likelihood of an unsustained free‐surface‐induced supershear rupture.