Upcycling red brick into a superior monolithic hydrogen evolution electrocatalyst

Abstract

Harvesting endogenous active metals from the natural and waste materials to develop efficient water splitting electrocatalysts is highly promising to afford a sustainable H2 economy. Herein, fired red brick (RB), a universal building material throughout the history without any other utilization purposes, is converted into a superior monolithic electrocatalyst for the H2 evolution reaction (HER) via the successive chemical vapor deposition (CVD) and low-temperature phosphidation. During CVD and phosphorization processes, the endogenous Fe species within RB efficiently catalyze the growth of N, P-codoped carbon nanotubes (N, P-CNTs) from melamine pyrolysis, leading to the formation of high-density and well-interconnected Fe-encapsulated N, P-CNTs firmly embedded throughout the entire RB substrate (Fe@N, P-CNTs/RB) with high conductivity, excellent mechanical strength, and uniformly distributed active sites. The as-fabricated Fe@N, P-CNTs/RB can be directly used as a monolithic electrode for the HER in a 0.5 M H2SO4 solution, requiring overpotentials of 223.6 and 285.6 mV to reach current densities of 10 and 100 mA cm-2, respectively, and exhibiting a excepetional stability for 100 h at 10 mA cm-2 with a overpotential increase of only 69.7 mV.