Methanol synthesis from CO₂ and H₂ via catalytic hydrogenation is already a commercialized and mature process. However, for methanol to serve as a practical energy carrier, further reductions in production cost and improvements in energy efficiency are essential. Key technological challenges include the development of low-cost, high-performance catalysts and the design of optimized reactors. In particular, Cu/ZnO catalysts remain the most widely used, and understanding their function is vital for designing next-generation systems. Recent advances in experimental and theoretical studies have significantly clarified the nature of active sites and reaction mechanisms, providing a foundation for targeted catalyst design. This chapter provides a detailed discussion of these findings, emphasizing the role of Cu-Zn synergy and surface intermediates. In addition, it addresses the importance of reactor engineering to manage the exothermic nature of the reaction and to effectively utilize the reaction heat. Shifting the equilibrium toward methanol production requires an integrated approach combining catalyst science, thermal management, and process optimization. Basic research, particularly that closely tied to industrial application, plays a central role in overcoming these barriers. This chapter concludes with a conceptual design of a cost-effective reactor system for improving methanol yield and energy efficiency.