A phosphite-incorporated crystalline–amorphous cobalt-based electrocatalyst via surface-confined chemical reduction for efficient hydrogen evolution reaction

Abstract

Targeted phase engineering of nanomaterials through non-equilibrium synthesis strategies provides a rich platform for the development and tuning of nanostructured catalysts with outstanding properties and advanced stability. Unconventional phases or even complex heterostructures play a crucial role in the performance of catalysts for efficient water electrolysis. By utilizing a controlled, iterative reduction synthesis route, a tailored binder-free cobalt boride-phosphite electrode (Co_xB-[0.2]P–O) with mixed crystalline–amorphous phases is developed. The tailored cobalt boride chemistry by phosphites enables the alteration of the d electron distribution of cobalt, bringing the H* adsorption energy into the optimal range and thereby enhancing the HER activity. Comprehensive microstructure and spectroscopic analyses proved the success of the one-pot strategy to modulate the microenvironment chemistry of cobalt by incorporating boron and phosphite. Moreover, the tailored formation of nanostructures with locally varying morphology by the co-existence of amorphous and crystalline phases on the nanometer scale is confirmed. This approach facilitates the rational design for tuning the metal boride-based catalysts' activity for hydrogen evolution by tailored chemistry of the metal active centers and thus the phase engineering of similar nanomaterials while avoiding the necessity of any thermal post-treatment processes.