LaNi1-xCoxO3 (x = 0, 0.3, 0.5) perovskite-type oxides were synthesized and evaluated as three-way catalysts (TWCs) for the simultaneous removal of CO, C3H6, and NO from automotive exhaust. TPR results revealed a progressive decrease in reduction temperatures upon cobalt incorporation, attributed to enhanced hydrogen spillover and improved oxygen mobility. FESEM and BET analyses showed pseudo-spherical morphologies with increased macroporosity but reduced surface areas and particle aggregation upon cobalt doping. XPS demon- strated enrichment of chemisorbed oxygen (Oad) and higher Ni3+/Ni2+ ratios with increasing cobalt content, correlating with enhanced redox properties. Optical characterization revealed band-gap narrowing from 2.40 eV (LaNiO3) to 2.31 eV (LaNi0.5Co0.5O3), favoring electron transfer. Catalytic activity tests demonstrated significant improvements in CO and C3H6 oxidation after cobalt substitution, with T50 for CO oxidation decreasing from 185 ◦C (LaNiO3) to 164.6 ◦C (LaNi0.5Co0.5O3), and T90 from 228.1 ◦C (LaNiO3) to 207.5 ◦C (LaNi0.5Co0.5O3). Similarly, T50 for C3H6 conversion reached 266.8 ◦C and T90 at 312.1 ◦C for LaNi0.5Co0.5O3, compared to 307.1 ◦C and 335.0 ◦C for pristine LaNiO3. Although NO conversion peaked at ~90% around 275 ◦C for LaNiO3, it decreased upon Co substitution due to equilibrium constraints. These findings demonstrate that cobalt incorporation enhances reducibility, lattice oxygen mobility, and surface oxygen reactivity, thereby promoting CO and hydrocarbon oxidation under TWC conditions. 1. Introduction Stringent emission standards for on-road vehicles are steadily lowering the allowable levels of carbon monoxide (CO), hydrocarbons (HCs), and nitrogen oxides (NOx), while also demanding catalysts that can sustain durability over long operational mileage [1–3]. Regulatory frameworks such as Euro 7, together with comparable international initiatives, emphasize the necessity for three-way catalysts (TWCs) that combine enhanced catalytic activity, superior thermal stability, and cost efficiency [4,5]. Regulations like Euro 7 and similar global initiatives highlight the need for advanced TWCs with high efficiency, durability, and low cost [4,5]. At the same time, the fluctuating availability and rising cost of platinum-group metals (PGMs), especially palladium (the dominant component in gasoline TWCs), highlight the importance of identifying PGM-lean or PGM-free alternatives that remain effective under realistic exhaust conditions [6–8]. Perovskite oxides (ABO3) have emerged as promising candidates to address

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