Proton conductors capable of operating in a high temperature range (over 200 degrees C) have received great interest for proton exchange membrane fuel cells (PEMFCs). Here, we report promising candidates for inorganic composite membranes for PEMFCs using solid CeP2O7/BPO4 and CeP2O7/BPO4/GO (without a liquid phase) at temperatures between 200 degrees C and 300 degrees C. BPO4 is prepared by combining a B3PO4 solution with an 85% H3PO4 solution, and it is loaded with CeP2O7. Furthermore, graphite oxide (GO) is incorporated with the CeP2O7/BPO4-based composite materials to improve the proton conductivity. The structure and phase stability of the membranes are analysed by X-ray diffraction, Fourier transform infrared (FTIR) and thermos-gravimetric analysis (TGA), and the microstructure morphology is analysed by scanning electron microscopy (SEM). The CeP2O7/BPO4 and CeP2O7/BPO4/GO composite electrolytes exhibit the high proton conductivities of 0.12 S cm(-1) and 0.14 S cm(-1) at 250 degrees C, respectively. Moreover, the peak power densities of the CeP2O7/BPO4/GO membrane are 149 mW cm(-2) at 200 degrees C, 240 mW cm(-2) at 250 degrees C and 184 mW cm(-2) at 300 degrees C. (C) 2016 Elsevier Ltd. All rights reserved.