Scanning transmission X-ray microscopy of hydrogen evolution electrocatalysts on reduction graphene oxide membranes

Cobalt is one of the promising metal catalysts for hydrogen evolution reaction, and its catalytic performance can be further improved by supporting on graphene oxide and reduced graphene oxide as an active interface to the substrate. Scanning transmission X-ray microscopy (STXM) identifies the position-dependent functional groups on the membranes and chemical structure evolution of the Co_xO_y. The in-situ mass spectrometer analysis shows the reduction current and H₂ generation of the electrocatalyst enhanced by the addition of graphene oxide and reduced graphene oxide to Co_xO_y, as compared to the Co_xO_y on the bare substrate. The best hydrogen evolution reaction performance of Co_xO_y at − 2.5 V is correlated with the high Co³⁺ concentration existed on the reduced graphene oxide, as evidenced by the nano- and element-resolved capability of STXM. With the economical electro-reduction synthesis, this study provides brand-new insights into the critical role of substrate rGO and electrocatalyst Co_xO_y toward the design of high efficiency electrocatalyst.