Quantum confined semiconductor nanocrystals have been widely investigated as light harvesting and charge separation components in photovoltaic and photocatalytic devices. The efficiency of these semiconductor nanocrystal-based devices depends on many processes, including light harvesting, carrier relaxation, charge separation and charge recombination. The competition between these processes determines the overall solar energy conversion (solar to electricity or fuel) efficiency. Compared with single component quantum dots (QDs), semiconductor nanoheterostructures, combining two or more materials, offer additional opportunities to control their charge separation properties by tailoring their compositions and dimensions through relative alignment of conduction and valence bands. Further integration of catalysts (heterogeneous or homogeneous) to these materials form multifunctional nanoheterostructures. Using Pt tipped CdSe/CdS dot-in-rod nanorods(NRs) and CdS nanoplatelets as model systems for 1D and 2D hetersotrtuctures, we are examining the mechanism of long-lived charge separation and H₂ generation in the presence of sacrificial electron donor. The rates of carrier transport, interfacial charge (electron and hole) transfer, and charge recombination can be directly monitored by transient absorption and time-resolved fluorescence spectroscopy. In this talk, we will discuss how the rates of these elementary carrier transfer and transport processes depend on the dimension (size and length), morphology and band alignment in these materials, affect the overall H2 generation efficiency and can be optimized through rational material design.