Toxic organics like dyes represent a major and growing source of environmental contamination. A promising method to remedy this uses semiconductors to catalytically photodegrade the stable bonds in these molecules. Heterostructured photocatalysts composed of two different semiconductors can overcome problems of fast electron-hole recombination and inefficient light harvesting whilst reducing dependency on either component individually. In this work, SnO2 nanowedges have been surface-modified with In2S3 nanoparticles to produce mSnO2-nIn2S3 (m:n = 1:2, 1:1, 2:1) heterostructures. The injection, by In2S3, of photoelectrons into the conduction band of SnO2, is argued to enhance charge stabilization and exciton lifetime. The photocatalytic degradation of methyl orange (MO) consequently reveals these nanocomposites to outperform their individual SnO2 and In2S3 components and industry standard TiO2. Sensitization of the SnO2 is explained by a strong type-II effect. The effects of varying SnO2:In2S3 are studied, leading us to propose a charge separation mechanism that explains why the nanocomposite containing the least photosensitizer (2SnO2-In2S3) offers the best photocatalysis per unit mass In.