With a theoretical maximum photocurrent of ca. 12.5 mA cm(-2) under AM 1.5 G 100 mW cm(-2) irradiation, the presently achieved plateau photocurrent of about 0.6 mA cm(-2) on bare LaTiO2N photoanodes indicates the presence of serious charge transport limitations. Only recently, a plateau photocurrent of about 4 mA cm(-2) was achieved on precious IrO2 modified LaTiO2N photoanodes prepared by a rather expensive and complex method, without discussing the intrinsic mechanism of improved photocurrents. In this study, by establishing highly crystalline porous LaTiO2N particles and superior inter-particle connectivity with reduced density of grain boundaries among the film particles, a record plateau photocurrent of 6.5 mA cm(-2) on the Co3O4 modified LaTiO2N photoanodesis demonstrated under AM 1.5 G 100 mW cm(-2) simulated sunlight. More broadly, this work shows the intrinsic requirements and significance of constituting (oxy)nitride particles for efficient charge transport and therefore desirable photoelectrochemical performances on the (oxy)nitride photoelectrodes, which have never been noticed and investigated before. With the obtained rules to follow are encouraging to explore the remaining substantial (oxy)nitride semiconductors as potential photoelectrodes for solar energy conversion.