Agaric-like cobalt diselenide supported by carbon nanofiber as an efficient catalyst for hydrogen evolution reaction

In situ doping Pt single atoms into 3D flower-like 1T-MoS2 via Pt-S bond for efficient hydrogen evolution reaction

Combining single atoms via phase transition engineering (from 2H to 1T) remains a challenge in MoS2-based catalysts. Herein, we report that Pt single atoms (PtSA) were doped into a 3D flower-like 1T-MoS2 catalyst (PtSA@MoS2) using a Pt-S bonding strategy. Doping with PtSA induced a phase transition in MoS2 from the 2H phase to the 1T phase. PtSA@MoS2 exhibited outstanding hydrogen evolution reaction (HER) performance, featuring an overpotential of 25 mV at 10 mA cm-2, a Tafel slope of 43.6 mV dec-1, and excellent long-term stability. The Pt-S first-shell scattering of PtSA@MoS2 in extended X-ray absorption fine structure (EXAFS) directly indicated that the PtSA was anchored near S atoms, forming Pt-S bonds. Furthermore, S atoms proximal to Pt functioned as catalytically active sites for HER, with Pt acting as an electron transfer mediator, facilitating the electron transfer from Mo to Pt and then to S. The p-band center of S showed a positive shift, indicating that PtSA@MoS2 interacted weakly with hydrogen, thereby accelerating the desorption of H atoms to generate H2. Additionally, PtSA@MoS2 exhibited a ΔGH* of only -0.13 eV, which also favored H2 production.

Anchoring Pt single atoms on 3D flower-like NiMoP via PtNi bonding with enhanced hydrogen evolution reaction

Introducing Pt single atoms (PtSA) into bimetallic phosphides to enhance their performance at higher current densities remains a significant challenge under alkaline conditions. We successfully anchored PtSA on 3D flower-like NiMoP through a PtNi bonding method. The 3D flower-like catalyst (PtSA@NiMoP) exhibits remarkably low overpotentials, requiring only 35 mV to achieve 10 mA cm-2 and 66 mV at 100 mA cm-2. Moreover, PtSA@NiMoP demonstrates a Tafel slope of 29.1 mV dec-1 and maintains stability for 50 h at different current densities in 1.0 M KOH solution. After the introduction of PtSA, the average NiNi bond length increases to 2.525 Å, accompanied by a significant decrease in the NiNi coordination number, indicating the successful formation of PtNi bonds. Density functional theory (DFT) calculations reveal that PtSA accelerates water dissociation on the NiMoP surface and facilitates electron transfer from Ni to P, enhancing H+ reduction and promoting the Volmer step. Additionally, the hydrogen adsorption Gibbs free energy (ΔGH*) of PtSA@NiMoP is only -0.065 eV (close to 0 eV), which is favorable for H2 evolution. Meanwhile, the Pt serves as an active site that further accelerates H2 generation, synergistically improving the catalytic kinetics of the alkaline hydrogen evolution reaction (HER).

Recent Advances in Co-Based Electrocatalysts for Hydrogen Evolution Reaction

Water splitting is a promising technique in the sustainable "green hydrogen" generation to meet energy demands of modern society. Its industrial application is heavily dependent on the development of novel catalysts with high performance and low cost for hydrogen evolution reaction (HER). As a typical non-precious metal, cobalt-based catalysts have gained tremendous attention in recent years and shown a great prospect of commercialization. However, the complexity of the composition and structure of newly-developed Co-based catalysts make it urgent to comprehensively retrospect and summarize their advance and design strategies. Hence, in this review, the reaction mechanism of HER is first introduced and the possible role of the Co component during electrocatalysis is discussed. Then, various design strategies that could effectively enhance the intrinsic activity are summarized, including surface vacancy engineering, heteroatom doping, phase engineering, facet regulation, heterostructure construction, and the support effect. The recent progress of the advanced Co-based HER electrocatalysts is discussed, emphasizing that the application of the above design strategies can significantly improve performance by regulating the electronic structure and optimizing the binding energy to the crucial intermediates. At last, the prospects and challenges of Co-based catalysts are shown according to the viewpoint from fundamental explorations to industrial applications.

Insight into selenium vacancies enhanced CoSe2/MoSe2 heterojunction nanosheets for hydrazine-assisted electrocatalytic water splitting

The integration of interface engineering and vacancy engineering was a feasible way to develop highly efficient electrocatalysts toward water electrolysis. Herein, we designed CoSe2/MoSe2 heterojunction nanosheets with abundant Se vacancies (VSe-CoSe2/MoSe2) for electrocatalytic water splitting. In the VSe-CoSe2/MoSe2 electrocatalyst, the electrons more easily transferred from CoSe2 to MoSe2, and interface engineering not only modulated the electronic structure, but also supplied more heterointerfaces and catalytic sites. After chemical etching, partial Se atoms were eliminated, which further activated the inert plane of the VSe-CoSe2/MoSe2 electrocatalyst and induced electron redistribution. The removal of surface Se atoms was also beneficial to expose inner reactive sites, which promoted adsorption toward reaction intermediates. Density functional theory calculations revealed that interface engineering and vacancy engineering collaboratively optimized the adsorption energy of the VSe-CoSe2/MoSe2 electrocatalyst toward the intermediate H* during the hydrogen evolution reaction process, leading to better electrocatalytic activity. The density of state diagram manifested the refined electronic structure of the VSe-CoSe2/MoSe2 electrocatalyst, and it exhibited a higher electronic state near the Fermi level, which indicated superior electronic conductivity, facilitating electron transport during the catalytic process. In alkaline media, the VSe-CoSe2/MoSe2 electrocatalyst delivered low overpotentials of merely 74 and 242 mV to obtain 10 mA cm-2 toward hydrogen evolution reaction and oxygen evolution reaction. This work illustrated the feasibility of combining two or more strategies to develop high-performance catalysts for water electrolysis.

Decorating Mg12O12 Nanocage with Late First-Row Transition Metals To Act as Single-Atom Catalysts for the Hydrogen Evolution Reaction

In the pursuit of sustainable clean energy sources, the hydrogen evolution reaction (HER) has attained significant interest from the scientific community. Single-atom catalysts (SACs) are among the most promising candidates for future electrocatalysis because they possess high thermal stability, effective electrical conductivity, and excellent percentage atom utilization. In the present study, the applicability of late first-row transition metals (Fe-Zn) decorated on the magnesium oxide nanocage (TM@Mg12O12) as SACs for the HER has been studied, via density functional theory. The late first-row transition metals have been chosen as they have high abundance and are relatively low-cost. Among the studied systems, results show that the Fe@Mg12O12 SAC is the best candidate for catalyzing the HER reaction as it exhibits the lowest activation barrier for HER. Moreover, Fe@Mg12O12 shows high stability (Eint = -1.64 eV), which is essential in designing SACs to prevent aggregation of the metal. Furthermore, the results of the electronic properties' analysis showed that the HOMO-LUMO gap of the nanocage is decreased significantly upon doping of Fe (from 4.81 to 2.28 eV), indicating an increase in the conductivity of the system. This study highlights the potential application of the TM@nanocage SAC systems as effective HER catalysts.