MXene with controlled surface termination groups for boosting photoelectrochemical water splitting

Abstract

Interface engineering is a promising strategy to optimize the interfacial photoelectrochemical (PEC) water-splitting system. However, previously, attention was paid to the engineering of the semiconductor/water interface and the other essential interface of the electrode/current collector was seriously undervalued. Herein, MXenes with controllable surface termination groups were synthesized using a molten salt etching method and used as electron transfer layer materials to modulate the interface between the semiconductor and the current collector. With BiVO₄ as a model photo-responsive material, the combination of Br-MXene significantly contributed to a 33% increase in the photocurrent density compared with the pristine BiVO₄-based photoelectrode. In addition, after attaching cobalt borate (CoBi) as a cocatalyst, the Br-MXene/BiVO₄/CoBi photoelectrode achieved a high photocurrent density of 5.47 mA cm⁻² at 1.23 V vs. RHE and photoconversion efficiency of 1.46%. The interface engineering strategy for efficient charge transfer is a promising and universal solution for the rational design of the photoelectrode and will inspire great research enthusiasm in the solar energy conversion fields.