Photoelectrochemical (PEC) water splitting offers a sparkling and sustainable strategy for hydrogen generation, and significant research for enhancing the conversion efficiency of electrocatalysts is underway, since a huge number of publications have been reported in this field. Hence, it is urgent to write a comprehensive and updated review in order to highlight the latest progress in the design, fabrication, and modification of electrocatalysts for high-efficiency PEC water splitting. In this review, we describe the basic mechanism of PEC water splitting utilizing electrocatalysts in detail. Further, we highlighted the recent advancements in the design, fabrication, and modification of high-efficiency electrocatalysts for energy conversion. In addition, the catalysts' surface passivation, heterojunction constructions, defect engineering, and photovoltage and photocurrent enhancements are also highlighted.