Photoelectrocatalysis stands at the forefront of transformative advancements in the chemical industry, offering a path toward a more sustainable future. Beyond water splitting and carbon dioxide reduction, photoelectrocatalysis has expanded into biomass upgrading and synthetic chemistry over the past decade. Semiconducting photoelectrodes enable redox reactions at interfaces with electrolytes, reducing energy demands and eliminating the need for toxic or costly homogeneous catalysts. This talk highlights two key photocatalytic organic transformations. First, we demonstrate the selective oxidation of benzyl alcohol to benzaldehyde using a bismuth vanadate (BiVO4) photoanode in acetonitrile, effectively avoiding benzoic acid formation. Our study uncovered the emergence of surface states formed between BiVO4 and the redox mediator, N-hydroxysuccinimide (NHS), leading to a gradual decline in photocurrent density. Using electrochemical impedance spectroscopy and intensity-modulated photocurrent spectroscopy, we probed carrier dynamics and found that NHS radical adsorption facilitates charge recombination. We propose optimized deposition methods and dopant incorporation to suppress these detrimental surface states. In a separate study, we tailored inverse spinel CuFe2O4 from n-type to p-type by tunning annealing temperature and atmosphere. By passivating oxygen vacancy donors and creating copper vacancy acceptors, we optimized the system for photocatalytic hydrogenation of benzaldehyde to benzyl alcohol, maintaining operational stability for over 16 hours. We further analyzed the influences of electrolytes and trace water impurities on the reduction reaction. Our findings underscore the importance of understanding the chemical and dynamic landscapes at the semiconductor-electrolyte junction to harness the full potential of photoelectrocatalysis, advancing molecular transformations with unique product selectivity.