B/N modified carbon nanofiber mesh covered with layered double hydroxide for large current overall water splitting

To realize cost-effective hydrogen production, a reasonable but challenging strategy is to develop nanocarbon-based material for large current overall water splitting (OWS). Here, this work synthesizes a monolithic nickel and iron layered double hydroxide covered B/N modified carbon nanofiber mesh grown on metal substrate, delineated as (BN-CNF@NiFe LDH)/NF, by electrochemical methods for high-performance OWS. To gain 100 mA cm−2 current density, this bifunctional material entails 238 mV and 126 mV overpotentials for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Evincing 500 and 1000 mA cm−2 current densities, an OWS system with two (BN-CNF@NiFe LDH)/NF electrodes solely calls for 1.69 and 1.92 V cell voltages under the industrial testing condition. Boron and nitrogen modified CNF mesh not merely raises the quantity of active sites via creating more hydrophilic surface area for electrodeposition of NiFe LDH, but also boosts the intrinsic activity via tuning the electron configurations of active species. As revealed by density functional theory (DFT), the charge density rearrangement between shell and core caused by B-N modification contributes to d band center shift. H adsorption favors the hollow site located at the center of three Ni atoms, while the existence of adjacent Fe indirectly facilitates the HER. This work contributes to the development of carbon-based monolithic material for large current OWS.