Electrosynthesis of Highly Efficient WObegin{document}$_{3-x}$end{document}/Graphene (Photo-)Electro- Catalyst by Two-Electrode Electrolysis System for Oxygen Evolution Reaction

Integration of non-noble transition metal oxides with graphene is known to construct high-activity electrocatalysts for oxygen evolution reduction (OER). In order to avoid the complexity of traditional synthesis process, a facile electrochemical method is elaborately designed to engineer efficient WObegin{document}$_{3-x}$end{document}/graphene (photo-)electrocatalyst for OER by a two-electrode electrolysis system, where graphite cathode is exfoliated into graphene and tungsten wire anode evolves into Vbegin{document}$_textrm{O}$end{document}-rich WObegin{document}$_{3-x}$end{document} profiting from formed reductive electrolyte solution. Among as-prepared samples, WObegin{document}$_{3-x}$end{document}/G-2 shows the best electrocatalytic performance for OER with an overpotential of 320 mV (without iR compensation) at 10 mA/cmbegin{document}$^2$end{document}, superior to commercial RuObegin{document}$_2$end{document} (341 mV). With introduction of light illumination, the activity of WObegin{document}$_{3-x}$end{document}/G-2 is greatly enhanced and its overpotential decreases to 290 mV, benefiting from additional reaction path produced by photocurrent effect and extra active sites generated by photogenerated carriers (hbegin{document}$^+$end{document}). Characterization results indicate that both Vbegin{document}$_textrm{O}$end{document}-rich WObegin{document}$_{3-x}$end{document} and graphene contribute to the efficient OER performance. The activity of WObegin{document}$_{3-x}$end{document} for OER is decided by the synergistic effect between Vbegin{document}$_textrm{O}$end{document} concentration and particle size. The graphene could not only disperse WObegin{document}$_{3-x}$end{document} nanoparticles, but also improve the holistic conductivity and promote electron transmission. This work supports a novel method for engineering WObegin{document}$_{3-x}$end{document}/graphene composite for highly efficient (photo-)electrocatalytic performance for OER.