We verify the existence of a lattice-matched type-II heterojunction and the ultrafast charge transfer process responsible for enhancing electron-hole separation. We grow epitaxially thin nanosheets onto nanotubes that absorb NIR radiation up to 1100 nm. Here, we report an efficient NIR-active photoanode by engineering a BiSeTe ternary alloy in the form of lattice-matched morphological heterojunctions (BST-MHs). When the morphological heterojunction is selected for a broadband absorption spectral range, and when it provides a low recombination rate, it offers avenues to increased energy conversion efficiencies. Lattice-matched morphological heterojunctions reduce carrier-trapping interfacial defects that generally exist at interfaces of two distinct semiconductors with large lattice mismatch 32, 33. With these considerations in mind, we focused on the development of NIR-active morphological heterostructures (MHs) with lattice-matched interfaces as a means to enhance the energy conversion efficiency of NBG semiconductors. Consequently, NIR absorber-based photoanodes have been limited to an incident photon-to-current conversion efficiency (IPCE) below 3% 18, 29, 30, 31. However, electron–phonon interactions and non-radiative recombination at defects have, until now, resulted in short-lived photoexcited carriers in these NBG semiconductors, a fact that prevents the needed surface redox reactions from proceeding efficiently 27. Narrow bandgap (NBG) semiconductors 18 that exhibit a wide NIR absorption range, a large absorption cross section, and long-lived charge carriers, offer a promising avenue toward NIR-active photoelectrodes that utilize band-edge carriers. Unfortunately, the low efficiency of upconversion luminescence and the short sub-picosecond lifetime of hot charge carriers lead to impractical photocurrent densities on the order of microamperes per square centimeter 26, 27, 28. Upconverting phosphors 23, 24 and metal plasmonic nanostructures 25 have previously been integrated into near-infrared (NIR) photoelectrodes (Supplementary Table 1). Extending optical absorption into the infrared region (IR, above 700 nm) enables further utilization of the remaining 50% of solar photon fluence and will promote these devices in toward the Shockley–Queisser (SQ) efficiency limit 17, 22. Improving the number of available photons to increase C h+ represents an important avenue to achieving high-efficiency photoanodes.Ī wide range of semiconductors 17, 18, 19, 20, 21 have shown application as photoanode materials however, their large bandgaps limit light absorption to the ultraviolet (UV, below 400 nm) and visible (vis, 400 to 700 nm) wavelengths. The primary obstacle limiting hole-involved photoelectrocatalytic reactions is the low concentration of photoholes ( C h+) that reach the surface of catalysts 14, 15, 16. However, the practical application of photoelectrochemical (PEC) hydrogen production is impeded today by its low energy conversion efficiency 9, 10, 11, 12, 13. The direct conversion of solar energy into chemical fuels offers a means to store renewable energy 1, 2, 3, 4, 5, 6, 7, 8. As a result, the photoanodes achieve an incident photon-to-current conversion efficiency of 36% at 800 nm in an electrolyte solution containing hole scavengers without a co-catalyst. The heterojunction’s hierarchical nanostructure separates charges at the lattice-matched interface of the two morphological components, preventing further carrier recombination. Specifically, we demonstrate a near-infrared-active morphological heterojunction comprised of BiSeTe ternary alloy nanotubes and ultrathin nanosheets. Here we introduce near-infrared-active photoanodes that feature lattice-matched morphological hetero-nanostructures, a strategy that improves energy conversion efficiency by increasing light-harvesting spectral range and charge separation efficiency simultaneously. However, solar conversion efficiencies are hindered by the fact that light harvesting has so far been of limited efficiency in the near-infrared region as compared to that in the visible and ultraviolet regions. Photoelectrochemical catalysis is an attractive way to provide direct hydrogen production from solar energy.