Corrosion engineering on AlCoCrFeNi high-entropy alloys toward highly efficient electrocatalysts for the oxygen evolution of alkaline seawater

Seawater splitting is a prospective approach to yield renewable and sustainable hydrogen energy.Complex preparation processes and poor repeatability are currently considered to be an insuperable impediment to the promotion of the large-scale production and application of electrocatalysts.Avoiding the use of intricate instruments,corrosion engineering is an intriguing strategy to reduce the cost and presents considerable potential for electrodes with catalytic performance.An anode comprising quinary AlCoCrFeNi layered double hydroxides uniformly decorated on an AlCoCrFeNi high-entropy alloy is proposed in this paper via a one-step corrosion engineering method,which directly serves as a remarkably active catalyst for boosting the oxygen evolution reaction(OER)in alkaline seawater.Notably,the best-performing catalyst exhibited oxygen evolution reaction activity with overpotential values of 272.3 and 332 mV to achieve the current densities of 10 and100 mA·cm^(-2),respectively.The failure mechanism of the obtained catalyst was identified for advancing the development of multicomponent catalysts.

Corrosion engineering boosting bulk Fe_(50)Mn_(30)Co_(10)Cr_(10)high-entropy alloy as high-efficient alkaline oxygen evolution reaction electrocatalyst

Oxygen evolution reaction(OER)is a critical process in electrocatalytic water splitting.However,the development of low-cost,highly efficient OER electrocatalysts by a simple method that can be used for industrial application on a large scale is still a huge challenge.Recently,high entropy alloy(HEA)has acquired extensive attention,which may provide answers to the current dilemma.Here,we report bulk Fe_(50)Mn_(30)Co_(10)Cr_(10),which is prepared by 3D printing on a large scale,as electrocatalyst for OER with high catalytic performance.Especially,an easy approach,corrosion engineering,is adopted for the first time to build an active layer of honeycomb nanostructures on its surface,leading to ultrahigh OER performance with an overpotential of 247 mV to achieve a current density of 10 mA cm^(-2),a low Tafel slope of 63 mV dec^(-1),and excellent stability up to 60 h at 100 mA cm^(-2)in 1 M KOH.The excellent catalytic activity mainly originates from:(1)the binder-free self-supported honeycomb nanostructures and multi-component hydroxides,which improve intrinsic catalytic activity,provide rich active sites,and reduce interfacial resistance;and(2)the diverse valence states for multiple active sites to enhance the OER kinetics.Our findings show that corrosion engineering is a novel strategy to improve the bulk HEA catalytic performance.We expect that this work would open up a new avenue to fabricate large-scale HEA electrocatalysts by 3D printing and corrosion engineering for industrial applications.

Dependence of corrosion resistance on grain boundary characteristics in a high nitrogen CrMn austenitic stainless steel

Processing schedules for grain boundary engineering involving different types of cold deformation（tension, compression, and rolling） and annealing were designed and carried out for 18Mn18Cr0.6N high nitrogen austenitic stainless steel. The grain boundary characteristic distribution was obtained and characterized by electron backscatter diffraction（EBSD） analysis. The corrosion resistance of the specimens with different grain boundary characteristic distribution was examined by using potentiodynamic polarization test. The corrosion behavior of different types of boundaries after sensitization was also studied.The fraction of low-∑ boundaries decreased with increasing strain, and it was insensitive to the type of cold deformation when the engineering strain was lower than 20%. At the strain of 30%, the largest and smallest fractions of low-∑ boundaries were achieved in cold-tensioned and rolled specimens, respectively. The fraction of low-∑ boundaries increased exponentially with the increase of grain size. The proportion of low-∑ angle grain boundaries increased with decreasing grain size. Increasing the fraction of low-∑ boundaries could improve the pitting corrosion resistance for the steels with the same grain size.After sensitization, the relative corrosion resistances of low-∑ angle grain boundaries, ∑3 boundaries, and ∑9 boundaries were 100%, 95%, and 25%, respectively, while ∑27 boundaries, other low-∑ boundaries and random high-angle grain boundaries had no resistance to corrosion.