This study introduces an innovative strategy for synthesizing low-cost, renewable carbon microspheres derived from potato starch. Uniformly dispersed potato-starch-based carbon microspheres (PCMs) were fabricated via a catalyst-free hydrothermal method, followed by calcination. Polyoxometalates (POMs) acted as both reducing and bridging agents, enabling the uniform deposition of silver nanoparticles (Ag NPs) on the PCM surface. The Ag NPs exhibited remarkable catalytic activity and a high specific surface area, effectively lowering the oxidation potential of adrenaline molecules and accelerating electron transfer, thereby enhancing detection sensitivity. As a biocarbon material, PCMs possess a high specific surface area and a porous structure, facilitating the adsorption and distribution of adrenaline molecules and thereby improving sensor performance. The synthesized ternary nanocomposite, Ag@POM/PCMs, exhibited synergistic catalytic behavior arising from the combined effects of catalytically active Ag NPs, electron-transfer-promoting POMs, and porous PCMs with a large surface area. This unique synergy significantly enhanced electrocatalytic performance, as demonstrated by high sensitivity, a broad linear detection range (0.46–1626.64 μM), and a low detection limit (0.238 μM, S/N = 3). Moreover, the material exhibited excellent stability, reproducibility, and anti-interference properties, achieving recovery rates of 99.2 % to 101.9 % in human serum samples.