This article presents a photoelectrochemical (PEC) cell design that simultaneously performs the direct oxidation of glycerol and the dark reduction of water or CO₂, achieving a high photocurrent density of over 110 mA cm⁻² under concentrated sunlight. The PEC cell uses an n-type silicon-based photoanode and a dark gas diffusion cathode, enabling selective glycerol oxidation without oxygen evolution reaction (OER). The study demonstrates that PEC methods can achieve higher selectivity and lower voltage requirements compared to electrochemical methods, especially at high current densities. The PEC cell design allows for the efficient conversion of glycerol into high-value products such as formic acid, acrolein, and lactic acid, while simultaneously reducing CO₂ or water. The study also highlights the importance of controlling operational parameters such as temperature, glycerol concentration, and anode potential to optimize product distribution and reaction efficiency. The results show that PEC methods can outperform traditional electrochemical approaches in terms of selectivity and energy efficiency, particularly when coupled with other electrochemical reactions. The study also addresses the challenges of scaling up PEC technologies, emphasizing the need for high-performance catalysts and semiconductors to achieve industrial relevance. The findings suggest that PEC methods have significant potential for future applications in electrochemical processes, especially when combined with other reactions to produce valuable products.This article presents a photoelectrochemical (PEC) cell design that simultaneously performs the direct oxidation of glycerol and the dark reduction of water or CO₂, achieving a high photocurrent density of over 110 mA cm⁻² under concentrated sunlight. The PEC cell uses an n-type silicon-based photoanode and a dark gas diffusion cathode, enabling selective glycerol oxidation without oxygen evolution reaction (OER). The study demonstrates that PEC methods can achieve higher selectivity and lower voltage requirements compared to electrochemical methods, especially at high current densities. The PEC cell design allows for the efficient conversion of glycerol into high-value products such as formic acid, acrolein, and lactic acid, while simultaneously reducing CO₂ or water. The study also highlights the importance of controlling operational parameters such as temperature, glycerol concentration, and anode potential to optimize product distribution and reaction efficiency. The results show that PEC methods can outperform traditional electrochemical approaches in terms of selectivity and energy efficiency, particularly when coupled with other electrochemical reactions. The study also addresses the challenges of scaling up PEC technologies, emphasizing the need for high-performance catalysts and semiconductors to achieve industrial relevance. The findings suggest that PEC methods have significant potential for future applications in electrochemical processes, especially when combined with other reactions to produce valuable products.