Scalable Synthesis of a Ruthenium-Based Electrocatalyst as a Promising Alternative to Pt for Hydrogen Evolution Reaction

Biomass-Derived Carbon-Based Multicomponent Integration Catalysts for Electrochemical Water Splitting

Electrocatalytic water splitting powered by sustainable electricity is a crucial approach for the development of new generation green hydrogen technology. Biomass materials are abundant and renewable, and the application of catalysis can increase the value of some biomass waste and turn waste into fortune. Converting economical and resource-rich biomass into carbon-based multicomponent integrated catalysts (MICs) has been considered as one of the most promising ways to obtain inexpensive, renewable and sustainable electrocatalysts in recent years. In this review, recent advances in biomass-derived carbon-based MICs towards electrocatalytic water splitting are summarized, and the existing issues and key aspects in the development of these electrocatalysts are also discussed and prospected. The application of biomass-derived carbon-based materials will bring some new opportunities in the fields of energy, environment, and catalysis, as well as promote the commercialization of new nanocatalysts in the near future.

Ultrathin Ti3C2Tx MXene sheets with high electrochemically active area anchored Pt boosting hydrogen evolution

To reduce platinum usage, ultrathin MXene sheets with little restacking effect were prepared. The ultrathin MXene was prepared by a two-step etching process, which showed high specific surface area with low charge transfer resistance. The sample showed a double layer capacity of 64.98 mF cm-2, which is 14 times as large as that of ordinary HF prepared MXene, indicating a larger electrochemically active surface area. It showed a much better HER performance of ∼190 mV at 10 mA cm-2. The better performance attributes to 0.4 wt% Pt loaded. The Pt loaded MXene exhibited a better HER performance of ∼75 mV at 10 mA cm-2 and a Tafel slope of 61.7 mV·dec-1 close to 40 wt% commercial Pt/C. The sample performed better than Pt/C in a 3 h chronopotentiometry test and hardly changed in ECSA after the cyclic experiment. With more Pt loading, the sample delivered better HER performance than Pt/C in the LSV test (∼51 mV at 10 mA cm-2). This work provides an effective route for the preparation of ultrathin MXene sheets with larger electrochemically active area and more active sites for Pt loading, leading to superior HER performance.

Thermal Puffing Promoting the Synthesis of N-Doped Hierarchical Porous Carbon-CoO x Composites for Alkaline Water Reduction

N-doped porous carbon-based catalysts hold great promise for hydrogen evolution reaction (HER) due to their plentiful cavity construction, high specific surface area, and flexible metal assemblies. Nevertheless, the cumbersome synthetic process and the use of highly corrosive chemicals greatly increase the production costs and pollutions. Herein, we report a facile and eco-friendly thermal puffing strategy, which imitates the popcorn forming process, for the fabrication of N-doped hierarchical porous carbon-CoO x catalysts. The results indicate that the well-developed porosity and high specific surface area (696 m2 g-1) of CoO x -NC-1.0 are achieved during the thermal expansion. Impressively, the as-prepared CoO x -NC-1.0 with ultralow Co loading (0.67 wt %) presents admirable HER performance to drive 10 mA cm-2 at an overpotential of 189 mV in the alkaline electrolyte. Especially, the activity of CoO x -NC-1.0 can be maintained for a continuous ∼70 h test. Such an excellent property of CoO x -NC not only derives from the hierarchical porous structure but is also due to the higher ratio of graphitic-N and pyridinic-N, which promotes the better electrical conductivity and formation of more active Co0 for HER, respectively. Moreover, this strategy is applicable to the fabrication of other transition metal-based hierarchical porous composites, which opens new possibilities for exploring promising candidates to substituted commercial Pt/C.

Excessive Se on RuSe2 nanocrystals to accelerate water dissociation for the enhanced electrocatalytic hydrogen evolution reaction

Selenium-enriched RuSe2 (RuxSe) nanocrystals as electrocatalysts for the HER in basic media have been synthesized via a facile hydrothermal method followed by a calcination process. The catalytic activity of the obtained RuxSe nanocrystals is greatly dependent on calcination temperatures. The nanocrystals obtained at 400 °C (RuxSe-400) demonstrate the highest HER activity with a low overpotential of 45 mV to deliver a current density of 10 mA cm-2 and a small Tafel slope of 31.4 mV dec-1. The enhanced catalytic HER performance of RuxSe-400 could be attributed to the excessive Se on the RuSe2 nanocrystal surface. Density functional theory (DFT) calculations reveal that the excessive Se would lower the energy barrier for water dissociation and lessen the dependence on the Ru sites for OH* adsorption but have a negligible effect on hydrogen adsorption energy, leading to an accelerated HER process. Furthermore, the excessive Se on the nanocrystal surface further endows the catalyst with promoted charge-transfer kinetics, ensuring a more efficient catalytic reaction. The strategy herein for the design of highly efficient HER catalysts by engineering the separation of different intermediate (H* and OH*) adsorption sites is expected to be extended to other electrocatalysts for high-efficiency energy conversion.

Electronic structural regulation of CoP nanorods by the tunable incorporation of oxygen for enhanced electrocatalytic activity during the hydrogen evolution reaction

The exploration of cost-effective and highly efficient electrocatalysts for the hydrogen evolution reaction (HER) is of great significance for realizing sustainable H₂ production. As previously proposed, anion incorporation in promising earth-abundant transition metal-based electrocatalysts could be a reasonable and competitive approach to regulate the electronic structure with optimized atomic hydrogen adsorption and desorption for enhanced intrinsic electrocatalytic performance during the HER. Herein, we present the rational design and fabrication of O-incorporated CoP (expressed as O-CoP) nanorods with a controllable component and electronic structure. As demonstrated, when the lattice-incorporated O is at an appropriate concentration, the engineered O-CoP nanocatalysts have more active sites exposed with an increased number of electrochemically active areas and better electron/ion conductivity, leading to boosted HER activity and running stability. Typically, the obtained O-CoP nanorods with an optimal oxygen content exhibit excellent HER activity with an overpotential of 116 mV at a current density of 10 mA cm^-2 and a small Tafel slope of 59 mV dec^-1 in alkaline media. This anion doping strategy may make a widespread contribution to the efficient engineering of electrocatalysts for energy conversion devices.

MOF-derived PdNiCo alloys encapsulated in nitrogen-doped graphene for robust hydrogen evolution reactions

The synergistic effect of PdNiCo nanoalloys and nitrogen-doped graphene for robust hydrogen evolution reactions.