The use of heterojunctions based on Rh-decorated WO3 nanorods is an effective strategy for achieving high-performance gas sensors for volatile organic compounds (VOCs), especially acetone (CH3COCH3). Herein, we successfully fabricated Rh-decorated WO3 nanorods with one-dimensional (1D) structures by glancing angle deposition (GLAD). Interestingly, morphological changes characterized by anomalous surfaces with numerous regions of negative curvature were observed upon decoration of the bare WO3 nanorods with Rh, which were systematically investigated on the basis of impeded surface diffusion and trapping effects. The improvements of gas sensing properties were stepwisely demonstrated by synergistic effects involving transition of Rh, high chemical potential of the negative curvature, primary decomposition at the top side, and highly ordered nanostructures. We are confident that the results provide new insight into the synthesis of effective nanostructures and contribute to a variety of applications including battery, solar water splitting, and sensor devices.