One important goal of the current electrocatalysis is to develop integrated electrodes from the atomic level design to multilevel structural engineering in simple ways and low prices. Here, a series of oxygen micro‐alloyed high‐entropy alloys (O‐HEAs) is developed via a metallurgy approach. A (CrFeCoNi)97O3 bulk O‐HEA shows exceptional electrocatalytic performance for the oxygen evolution reaction (OER), reaching an overpotential as low as 196 mV and a Tafel slope of 29 mV dec−1, and with stability longer than 120 h in 1 m KOH solution at a current density of 10 mA cm−2. It is shown that the enhanced OER performance can be attributed to the formation of island‐like Cr2O3 microdomains, the leaching of Cr3+ ions, and structural amorphization at the interfaces of the domains. These findings offer a technological‐orientated strategy to integrated electrodes.

Metallic glasses (MGs) are amorphous alloys with a number of unique properties that are attractive for the fundamental understanding of the nature and applications of disordered systems [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. Generally, MGs might be grouped into two categories based on their glass forming ability (i.e., the ease of glass formation by cooling a liquid): in one case, large or bulk volumes may be slowly cooled to the glassy state from the melt. This category is usually called as bulk metallic glass formers [18][19][20][21][22]. In contrast, certain MGs, represented by aluminum (Al)- [23,24] and some iron (Fe)- [25,26] based MGs, can be synthesized mainly by rapid solidification processes such as melt spinning or vapor deposition. These MGs are often denoted as marginal MG-formers [23][24][25].With the rapid developments of MGs, many previously identified marginal glass formers have been successfully made into bulk metallic glasses by composition strategies (such as Fe-and Ni-based MGs) [8,25,26,28]. However, one remarkable exception is the family of Al-based MGs [23,24]. Although there have been continuous efforts in optimizing compositions and improving processing techniques since its first discovery [29] several decades ago, the glass forming ability of Al-MGs is still limited nowadays [23,30,31]. Recently, Wu et al. [30] reported that the hitherto best glass forming ability for Al-MGs is from Al 86 Ni 6.75 Co 2.25 Y 3.25 La 1.75 with a fully glassy rod of 1.5 mm in diameter. Although the glassy rod can reach 2.5 mm for the same composition after a refined fluxtreatment of the liquid [31], this critical size is still much smaller than those of typical Zr-based MGs (~75 mm) [32], Mg-MGs (25 mm) [18] and Pd-MGs (80 mm) [33]. Moreover, the glass forming ability of Al-MGs is very sensitive to compositions. Only a few percent change of the constituting elements would dramatically reduce this critical size [21,27,30,34,35]. Consequently, it is more difficult to develop Al-MGs than other MGs. Fundamentally, it remains to be a puzzling issue why the Al-MGs are so unique [27,30,36].Among several factors, one clue for the distinction between bulk glasses and marginal glass formers is based upon their supercooled liquids [19,23,26,27]. The change of the relaxation dynamics (e.g., viscosity, diffusivity or relaxation time) with the temperature is highly materialspecific. Angell introduced the concept of fragility (m) for the classification of glass-forming materials, which was defined as the apparent activation energy of relaxation time τ α normalized to glass transition temperature T g : m = dlog(τ α )/(dT g /T)| T=T g [37]. A stronger deviation from Arrhenius behavior (with a larger m value) corresponds to a more fragile system; otherwise, the system is strong [37][38][39][40]. Wang et al. [41] theoretically pointed out that the fragility index for non-polymeric glasses should have a lower limit m = 16.5, and an upper limit m~175.Recently, Johnson et al.[42] conducted a critical asses...