Artificial photosynthesis can potentially address the global energy challenges and environmental issues caused by fossil fuels. Photoelectrochemical heterojunction structures of new photonic structures have been developed for efficient sunlight absorption, charge generation and separation and transport, and selective reduction of CO₂ and water splitting. In this review, an overview of several recently developed heterojunction model systems comprised of low-cost photonic materials such as transition metal dichalcogenides (TMDs), perovskite semiconductor nanocrystals, and plasmonic nanostructures is presented to rationalize the potential benefits of utilizing heterojunction structures for efficient and selective CO₂ reduction with renewable energy resources. Recent advances in electroanalytical methods for CO₂ reduction such as scanning electrochemical microscopy (SECM) are reviewed. These techniques can potentially resolve local CO₂ reduction kinetics and their spatial heterogeneities of a heterojunction photoelectrochemical structure.