Perovskite oxides (ABO3) with flexibility structural and chemical properties have attracted wide attention in the electrocataly water splitting. However, its poor intrinsic activity and unsuitable adsorption energy for oxygenated species...

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hydrogen evolution reaction (HER) owing to its optimal hydrogen adsorption energy and excellent stability. [5,6] However, its high cost and scarcity seriously limit its largescale commercialization. [7,8] Furthermore, its catalytic activity for alkaline HER is greatly decreased compared to that for acidic HER, which is primarily hindered by a sluggish water dissociation step in the alkaline electrolytes. [9][10][11][12] Therefore, a central challenge for Pt-based electrocatalysts is how to increase the intrinsic mass activity (MA) of Pt and lower the water dissociation energy barrier for the alkaline HER. [5,6,8,[13][14][15][16][17][18] To this end, intense research efforts focus on developing various approaches to improving the MA of Pt. [14][15][16][17][18][19] A common strategy is to alloy Pt with 3d transition metals (Fe, Co, Ni, W, etc.), or nonmetallic atoms (such as P, S, Se, and Te). For instance, the integration of Pt with P-forming platinum phosphide has proven effective in enhancing its catalytic activity, electron structure, and binding properties. [32][33][34] However, the bond between Pt atoms is extremely strong with a large bond energy of 306.7 kJ mol −1 resulting in the difficulty in breaking the Pt-Pt bond and introducing P into the Pt lattice to form platinum phosphide, [31] which normally requires either a high reaction temperature (>800 °C) or use of reactive and toxic organophosphorus precursors and dangerous white/red phosphorus. [35][36][37][38] Thus, the mild synthesis of platinum phosphide remains a Electrocatalytic hydrogen evolution reaction (HER) in alkaline media is important for hydrogen economy but suffers from sluggish reaction kinetics due to a large water dissociation energy barrier. Herein, Pt 5 P 2 nanocrystals anchoring on amorphous nickel phosphate nanorods as a high-performance interfacial electrocatalyst system (Pt 5 P 2 NCs/a-NiPi) for the alkaline HER are demonstrated. At the unique polycrystalline/amorphous interface with abundant defects, strong electronic interaction, and optimized intermediate adsorption strength, water dissociation is accelerated over abundant oxophilic Ni sites of amorphous NiPi, while hydride coupling is promoted on the adjacent electron-rich Pt sites of Pt 5 P 2 . Meanwhile, the ultra-small-sized Pt 5 P 2 nanocrystals and amorphous NiPi nanorods maximize the density of interfacial active sites for the Volmer-Tafel reaction. Pt 5 P 2 NCs/a-NiPi exhibits small overpotentials of merely 9 and 41 mV at −10 and −100 mA cm −2 in 1 M KOH, respectively. Notably, Pt 5 P 2 NCs/a-NiPi exhibits an unprecedentedly high mass activity (MA) of 14.9 mA µg Pt −1 at an overpotential of 70 mV, which is 80 times higher than that of Pt/C and represents the highest MA of reported Pt-based electrocatalysts for the alkaline HER. This work demonstrates a phosphorization and interfacing strategy for promoting Pt utilization and in-depth mechanistic insights for the alkaline HER.

The rational design of efficient and cost‐effective electrocatalysts for oxygen evolution reaction (OER) with sluggish kinetics, is imperative to diverse clean energy technologies. The performance of electrocatalyst is usually governed by the number of active sites on the surface. Crystalline/amorphous heterostructure has exhibited unique properties and opens new paradigms toward designing electrocatalysts with abundant active sites for improved performance. Hence, Fe doped Ni–Co phosphite (Fe‐NiCoHPi) electrocatalyst with cauliflower‐like structure, comprising crystalline@amorphous core–shell nanorod, is reported. The experiments uncover that Fe is enriched in the amorphous shell due to the flexibility of the amorphous component. Further density functional theory calculations indicate that the strong electronic interaction between the enriched Fe in the amorphous shell and crystalline core host at the core–shell interface, leads to balanced binding energies of OER intermediates, which is the origin of the catalyst‐activity. Eventually, the Fe‐NiCoHPi exhibits remarkable activity, with low overpotentials of only 206 and 257 mV at current density of 15 and 100 mA cm−2. Unceasing durability over 90 h is achieved, which is superior to the effective phosphate electrocatalysts. Although the applications at high current remain challenges , this work provides an approach for designing advanced OER electrocatalysts for sustainable energy devices.

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