Conversion of Catalytically Inert 2D Bismuth Oxide Nanosheets for Effective Electrochemical Hydrogen Evolution Reaction Catalysis via Oxygen Vacancy Concentration Modulation

Oxygen vacancies(Vo)in electrocatalysts are closely correlated with the hydrogen evo-lution reaction(HER)activity.The role of vacancy defects and the effect of their concentration,how-ever,yet remains unclear.Herein,Bi2O3,an unfavorable electrocata-lyst for the HER due to a less than ideal hydrogen adsorption Gibbs free energy(ΔGH*),is utilized as a perfect model to explore the func-tion of Vo on HER performance.Through a facile plasma irradia-tion strategy,Bi2O3 nanosheets with different Vo concentrations are fabricated to evaluate the influence of defects on the HER process.Unexpectedly,while the generated oxygen vacancies contribute to the enhanced HER performance,higher Vo concentrations beyond a saturation value result in a significant drop in HER activity.By tunning the Vo concentration in the Bi_(2)O_(3)nanosheets via adjusting the treatment time,the Bi2O3 catalyst with an optimized oxygen vacancy concentration and detectable charge carrier concentration of 1.52×10^(24)cm^(−3)demonstrates enhanced HER performance with an overpotential of 174.2 mV to reach 10 mA cm^(−2),a Tafel slope of 80 mV dec−1,and an exchange current density of 316 mA cm−2 in an alkaline solution,which approaches the top-tier activity among Bi-based HER electrocatalysts.Density-functional theory calculations confirm the preferred adsorption of H*onto Bi2O3 as a function of oxygen chemical potential(ΔμO)and oxygen partial potential(PO2)and reveal that high Vo concentrations result in excessive stability of adsorbed hydrogen and hence the inferior HER activity.This study reveals the oxygen vacancy concentration-HER catalytic activity relationship and provides insights into activating catalytically inert materials into highly efficient electrocatalysts.

Hierarchical Ni_(3)S_(4)@MoS_(2)nanocomposites as efficient electrocatalysts for hydrogen evolution reaction

Hydrogen evolution reaction(HER)through water splitting is a promising way to solve the energy shortage.Noble-metal-free HER electrocatalysts with high efficiency is very important for practical applications.Herein,we prepare the Ni_(3)S_(4)@MoS_(2)electrocatalyst on carbon cloth(CC)through a two-step hydrothermal process.The Ni_(3)S_(4)nanorods are uniformly integrated with the MoS_(2)nanosheets,forming a hierarchical structure and heterogeneous interfaces.The fast electron transfer on the interface enhances the kinetics of catalytic reaction.The hierarchical structure provides more exposed active sites.The Ni_(3)S_(4)@MoS_(2)/CC exhibits good catalytic activity and long-term stability for HER.This work provided a practicable strategy to develop efficient electrocatalysts for HER in alkaline media.

Se-Ni Se_(2) hybrid nanosheet arrays with self-regulated elemental Se for efficient alkaline water splitting

Understanding the catalytic mechanism of non-noble transition metal electrocatalysts is crucial to designing high-efficiency,low-cost,and durable alternative electrocatalysts for water splitting which comprises the hydrogen evolution reaction(HER) and oxygen evolution reaction(OER).In this work,Se-NiSe_(2) hybrid nanosheets with a self-regulated ratio of ionic Se(I-Se) to elemental Se(E-Se) are designed on carbon cloth by solution synthesis and hydrothermal processing.The effects of the I-Se/E-Se ratios on the electrocatalytic characteristics in HER and OER are investigated systematically both experimentally and theoretically.The optimized bifunctional electrocatalyst needs overpotentials of only 133 mV to deliver an HER current density of 10 mA cm^(-2) and 350 mV to generate an OER current density of 100 mA cm^(-2) in1.0 mol L^(-1) KOH.Based on the density-functional theory calculation,surface-adsorbed E-Se is beneficial to optimizing the electron environment and the adsorption/desorption free energy of hydrogen/water of the hybrid catalyst,consequently facilitating the electrocatalytic water splitting process.There is a proper I-Se/E-Se ratio to improve the catalytic activity and kinetics of the reaction and the optimized E-Se adsorption amount can balance the interactions between I-Se and E-Se,so that the catalyst can achieve appropriate Se-H binding and active site exposure for the excellent electrocatalytic activity.To demonstrate the practicality,the assembled symmetrical device can be powered by an AA battery to produce hydrogen and oxygen synchronously.Our results provide a deeper understanding of the catalytic mechanism of transition metal selenides in water splitting and insights into the design of high-efficiency and low-cost electrocatalysts in energy-related applications.

Planarization mechanism of alkaline copper CMP slurry based on chemical mechanical kinetics

The planarization mechanism of alkaline copper slurry is studied in the chemical mechanical polishing （CMP） process from the perspective of chemical mechanical kinetics.Different from the international dominant acidic copper slurry,the copper slurry used in this research adopted the way of alkaline technology based on complexation. According to the passivation property of copper in alkaline conditions,the protection of copper film at the concave position on a copper pattern wafer surface can be achieved without the corrosion inhibitors such as benzotriazole（BTA）,by which the problems caused by BTA can be avoided.Through the experiments and theories research,the chemical mechanical kinetics theory of copper removal in alkaline CMP conditions was proposed. Based on the chemical mechanical kinetics theory,the planarization mechanism of alkaline copper slurry was established. In alkaline CMP conditions,the complexation reaction between chelating agent and copper ions needs to break through the reaction barrier.The kinetic energy at the concave position should be lower than the complexation reaction barrier,which is the key to achieve planarization.

Three-dimensional-printed Ni-based scaffold design accelerates bubble escape for ampere-level alkaline hydrogen evolution reaction

Alkaline hydrogen evolution reaction(HER)for scalable hydrogen production largely hinges on addressing the sluggish bubble-involved kinetics on the traditional Ni-based electrode,especially for ampere-level current densities and beyond.Herein,3D-printed Ni-based sulfide(3DPNS)electrodes with varying scaffolds are designed and fabricated.In situ observations at microscopic levels demonstrate that the bubble escape velocity increases with the number of hole sides(HS)in the scaffolds.Subsequently,we conduct multiphysics field simulations to illustrate that as the hole shapes transition from square,pentagon,and hexagon to circle,where a noticeable reduction in the bubble-attached HS length and the pressure balance time around the bubbles results in a decrease in bubble size and an acceleration in the rate of bubble escape.Ultimately,the 3DPNS electrode with circular hole configura-tions exhibits the most favorable HER performance with an overpotential of 297 mV at the current density of up to 1000 mA cm^(-2) for 120 h.The present study highlights a scalable and effective electrode scaffold design that promotes low-cost and low-energy green hydrogen production through the ampere-level alkaline HER.