Low Platinum-Loaded Molybdenum Co-catalyst for the Hydrogen Evolution Reaction in Alkaline and Acidic Media

Platinum Cluster Decoration on Hollow Carbon Spheres for High-Efficiency Hydrogen Evolution Reaction

Currently, platinum (Pt)/carbon support composite materials have tremendous application prospects in the hydrogen evolution reaction (HER). However, one of the primary challenges for boosting their performance is designing a substrate with the desired microstructure. Herein, the intact hollow carbon spheres (HCSs) were prepared via template method. Based on the morphology variation of the as-prepared HCSs-x, we conjectured that the polydopamine (PDA) core was generated first and then slowly grew into a complete overburden (SiO2@PDA). Afterward, Pt atomic clusters were anchored on the outer shells of HCSs-4 to construct composite electrocatalysts (Pty/HCSs-4) by a chemical reduction method. Due to the low charge-transfer resistance, the HCSs have a large electrochemical surface area and provide a continuous electron transport pathway, boosting the atom utilization efficiency during hydrogen production and release. The synthesized Pt2.5/HCSs-4 electrocatalysts exhibit excellent HER activity in acidic media, which can be ascribed to the compositional modulation and delicate structural design. Specifically, when the overpotential is 10 A g-1, the overpotential can achieve 92 mV. This work opens a new route to fabricate Pt-based electrocatalysts and brings a new understanding of the formation mechanism of HCSs.

Spontaneous Deposition of Single Platinum Atoms on Anatase TiO2 for Photocatalytic H2 Evolution

Single-atom (SA) decoration has emerged as a frontier in catalysis due to its unique characteristics. Recently, decorated Pt single atoms on titania have shown promise in photocatalytic hydrogen evolution. In this work, we demonstrate that Pt SAs can spontaneously deposit on the surface, driven by electrostatic forces; the key is to determine the golden pH and surface potential. We conducted a comprehensive investigation into the influence of the pH of the deposition precursor on the spontaneous adsorption of Pt SAs onto TiO2 nanosheets (TiNSs). We introduced a straightforward pH-dependent and charge-dependent strategy for the solid electrostatic anchoring of Pt SAs on TiO2. Furthermore, we established that the level of Pt loading can be controlled by adjusting the precursor pH. X-ray photoelectron spectroscopy (XPS) and high-angle annular dark-field imaging scanning transmission electron microscopy (HAADF-STEM) were used to evaluate the Pt SA-decorated samples. Photocatalytic hydrogen production activity was assessed under ultraviolet (UV) (365 nm) irradiation. Notably, we found that at a pH of 8, slightly below the measured point of zero charge (PZC), a unique mixture of Pt clusters and single atoms was deposited on the surface of TiNSs. This unique composition significantly improved hydrogen production, resulting in ∼3.7 mL of hydrogen generated after 8 h of UV exposure by only 10 mg of the Pt-decorated TiNS (with Pt loadings of 0.12 at. %), which is ∼300 times higher than the undecorated TiNS.

Ultrasonic-assisted preparation of two-dimensional materials for electrocatalysts

Developing green, environmental, sustainable new energy sources is an important problem to be solved in the world. Among the new energy technologies, water splitting system, fuel cell technology and metal-air battery technology are the main energy production and conversion methods, which involve three main electrocatalytic reactions, hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR). The efficiency of the electrocatalytic reaction and the power consumption are very dependent on the activity of the electrocatalysts. Among various electrocatalysts, the two-dimensional (2D) materials have received widespread attention due to multiple advantages, such as their easy availability and low price. What' important is that they have adjustable physical and chemical properties. It is possible to develop them as electrocatalysts to replace the noble metals. Therefore, the design of two-dimensional electrocatalysts is a focus in the research area. Some recent advances in ultrasound-assisted preparation of two-dimensional (2D) materials have been overviewed according to the kind of materials in this review. Firstly, the effect of the ultrasonic cavitation and its applications in the synthesis of inorganic materials are introduced. The ultrasonic-assisted synthesis of representative 2D materials for example transition metal dichalcogenides (TMDs), graphene, layered double metal hydroxide (LDH), and MXene, and their catalytic properties as electrocatalysts are discussed in detail. For example, the CoMoS₄ electrocatalysts have been synthesized through a facile ultrasound-assisted hydrothermal method. The obatined HER and OER overpotential of CoMoS₄ electrode is 141 and 250 mV, respectively. This review points out some problems that need to be solved urgently at present, and provides some ideas for designing and constructing two-dimensional materials with better electrocatalytic performance.

Hierarchical CoMoS3.13/MoS2 hollow nanosheet arrays as bifunctional electrocatalysts for overall water splitting

Hollow hetero-nanosheet arrays have attracted great attention due to their efficient catalytic abilities for water splitting. We successfully fabricated ZIF-67-derived hollow CoMoS_3.13/MoS₂ nanosheet arrays on carbon cloth in situ through a two-step heating-up hydrothermal method, in which the MoS₂ nanosheets were suitably distributed on the surface of the hollow CoMoS_3.13 nanosheet arrays. There was a distinct synergistic effect between CoMoS_3.13 and MoS₂, and a large number of defective and disordered interfaces were formed, which improved the charge transfer rate and provided abundant electrochemical active sites. CMM 0.5, with the optimal Mo doping concentration of 0.5 mmol, exhibited the best catalytic properties. The overpotential values of CMM 0.5 at 10 mA cm^-2 were only 107 and 169 mV for the HER and OER, respectively, and it had nearly 100% faradaic efficiency. A dual-electrode electrolytic cell assembled with CMM 0.5 required a voltage of only 1.507 V at 10 mA cm^-2 for overall water splitting, and it displayed remarkable long-term durable bifunctional stability.