Boosting CdS Photocatalytic Activity for Hydrogen Evolution in Formic Acid Solution by P Doping and MoS2 Photodeposition

Abstract

Formic acid is an appealing hydrogen storage material. In order to rapidly produce hydrogen from formic acid under relatively mild conditions, high-efficiency and stable photocatalytic systems are of great significance to prompt hydrogen (H2) evolution from formic acid. In this paper, an efficient and stable photocatalytic system (CdS/P/MoS2) for H2 production from formic acid is successfully constructed by elemental P doping of CdS nanorods combining with in situ photodeposition of MoS2. In this system, P doping reduces the band gap of CdS for enhanced light absorption, as well as promoting the separation of photogenerated charge carriers. More importantly, MoS2 nanoparticles decorated on P-doped CdS nanorods can play as noble-metal-free cocatalysts, which increase the light adsorption, facilitate the charge transfer and effectively accelerate the hydrogen evolution reaction. Consequently, the apparent quantum efficiency (AQE) of the designed CdS/P/MoS2 is up to 6.39% at 420 nm, while the H2 evolution rate is boosted to 68.89 mmol·g−1·h−1, which is 10 times higher than that of pristine CdS. This study could provide an alternative strategy for the development of competitive CdS-based photocatalysts as well as noble-metal-free photocatalytic systems toward efficient hydrogen production.

Recent Breakthroughs and Future Potential of Inorganic Nanocomposites in Hydrogen Generation

“…Furthermore, the deposition of MoS 2 over P‐doped CdS NPs (in situ) generates metal‐free cocatalysts to escalate the efficiency. This route enhances light adsorption efficiency and extends charge carrier separation and apparent quantum efficiency (AQE) at 420 nm, showing a 10 times higher rate of 68.89 mmol/g/h than its pristine form [122] …”

“…This route enhances light adsorption efficiency and extends charge carrier separation and apparent quantum efficiency (AQE) at 420 nm, showing a 10 times higher rate of 68.89 mmol/g/h than its pristine form. [122] Besides, the distinct behavior of semiconductor-based composite photocatalysts provides a new avenue for energy transformation. It exhibits higher potential when doped to synthesize a heterojunction system.…”

Heterojunction catalysts for CO2–HCOOX interconversion cycles

“…146,147 Semiconductor photocatalysts are favored by researchers, but there are still some problems such as easy recombination of the photogenerated charge, low energy utilization, and poor catalytic activity. 148 The heterojunction catalyst can achieve efficient photogenerated charge separation through the design of the interface electronic structure and tune the electron density of the active site to further change the adsorption energy of key intermediate species in the reaction path, so as to improve the above problems. 149 The heterojunction photocatalysts composed of semiconductor and metal-based cocatalysts have been extensively investigated to enhance the activity of solar-driven HCOOX dehydrogenation.…”

“…Non-noble metals based on heterojunction catalysts are the potential candidates for the photocatalytic dehydrogenation of formate. 147,148,152 Besides the metals, some metal carbides, nitrides, and phosphides also exhibit metallic properties and can therefore be used to construct metal-based heterojunctions. Among the non-noble metal based catalysts, the corresponding transition-metal phosphides (TMPs) with good conductivity and high chemical stability have been widely investigated in various photocatalytic systems and exhibit superior photocatalytic performances.…”