Several of the cost and efficiency bottlenecks in the design of a photoelectrocatalytic device for solar fuels production arise from the need for electrocatalyst materials that can resist a corrosive reaction environment, while enabling the accelerated breaking and making, at low temperatures, of highly energetic chemical bonds such as CO, C–H, O–H etc. Promising tools for high-throughput synthesis and screening have been developed, and their use will be most efficient with the guidance of a catalyst blueprint that is based on a thorough understanding of physical key parameters that determine catalyst stability, activity and selectivity. These parameters are encoded in the surface electronic structure of any given catalyst material, and can be interrogated with well-established surface science methods such as electron spectroscopy and electron diffraction. A challenge, however, that has limited the success of traditional surface science in electrochemistry, is the sometimes drastic modification of the catalyst surface in the electrochemical environment. This chapter reviews the contributions of surface science to the development of improved catalysts for solar fuels generation, and the development of advanced synchrotron X-ray spectroscopy methods towards probing catalysts in the presence of electrolyte and, ultimately, under realistic operating conditions.