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Developing protocols for designing high‐efficiency, durable, cost‐effective electrocatalysts for oxygen evolution reaction (OER) necessitates deeper understanding of structure–property correlation as a function of composition. Herein, it has been demonstrated that incorporating tellurium into binary nickel chalcogenide (NiSe) and creating a mixed anionic phase perturbs its electronic structure and significantly enhances the OER activity. A series of nanostructured nickel chalcogenides comprising a layer‐by‐layer morphology along with mixed anionic ternary phase are grown in situ on nickel foam with varying morphological textures using simple hydrothermal synthesis route. Comprehensive X‐ray diffraction, X‐ray photoelectron spectroscopy, and in situ Raman spectroscopy analysis confirms the formation of a trigonal single‐phase nanocrystalline nickel (telluro)‐selenide (NiSeTe) as a truly mixed anionic composition. The NiSeTe electrocatalyst exhibits excellent OER performance, with a low overpotential of 300 mV at 50 mA cm⁻²and a small Tafel slope of 98 mV dec⁻¹in 1 mKOH electrolyte. The turnover frequency and mass activity are 0.047 s⁻¹and 90.3 Ag⁻¹, respectively. Detailed electrochemical measurements also reveal enhanced charge transfer properties of the NiSeTe phase compared to the mixture of binaries. Density functional theory calculations reveal favorable OH adsorption energy in the mixed anionic phase compared to the binary chalcogenides confirming superior electrocatalytic property. 

Elastocaloric cooling, a solid-state cooling technology, exploits the latent heat released and absorbed by stress-induced phase transformations. Hysteresis associated with transformation, however, is detrimental to efficient energy conversion and functional durability. We have created thermodynamically efficient, low-hysteresis elastocaloric cooling materials by means of additive manufacturing of nickel-titanium. The use of a localized molten environment and near-eutectic mixing of elemental powders has led to the formation of nanocomposite microstructures composed of a nickel-rich intermetallic compound interspersed among a binary alloy matrix. The microstructure allowed extremely small hysteresis in quasi-linear stress-strain behaviors—enhancing the materials efficiency by a factor of four to seven—and repeatable elastocaloric performance over 1 million cycles. Implementing additive manufacturing to elastocaloric cooling materials enables distinct microstructure control of high-performance metallic refrigerants with long fatigue life.