Developing a bifunctional electrocatalyst with remarkable performance viable for overall water splitting is increasingly essential for industrial-scale renewable energy conversion. However, the current electrocatalyst still requires a large cell voltage to drive water splitting due to the unsuitable adsorption/desorption capacity of reaction intermediates, which seriously hinders the practical application of water splitting. Herein, a unique SiO x /Ru nanosheet (NS) material was proposed as a high-performance electrocatalyst for overall water splitting. The SiO x /Ru NSs show superior performance in the hydrogen evolution reaction with a low overpotential of 23 mV (@ 10 mA cm −2 ) and excellent stability for nearly 200 h (@ 10 mA cm −2 ) in 1 M KOH. By means of the introduction of SiO x , it is beneficial for balancing the local charge density of the surrounding Ru sites. The suitable electronic coupling between the d-band electrons of Ru and the adsorbed species effectively balances the adsorption and desorption of reaction intermediates on the surface. As a result, the catalyst also exhibits overall water splitting activity with a cell voltage of only 1.496 V to reach the current density of 10 mA cm −2 . The present work opens up a new strategy for designing highperformance electrocatalysts for water splitting.
Doping in Si nanocrystals (Si NCs) is an interesting topic since the doping behaviors in the nanoscale are quite complicated compared with the case in bulk Si. In our present work, we use the first-principles calculation to study Phosphorus (P) or Boron (B) doping in Si NCs with the size of 2-8 nm embedded in SiO2 matrix by taking into account the existence of dangling bonds on the interfacial region. It is found that both P and B impurities tend to stay at the interfacial region to passivate the dangling bonds when the dot size is as small as 2 nm. However, P impurities exhibit the possibility to occupy the inner sites of Si NCs while B impurities are more difficult to be introduced into Si NCs due to the large formation energy. Our detailed study suggests that P or B impurities preferentially stay at the intermediate sites between Si and oxygen to form stable bonding configurations. With increasing the dot size from 2 nm to 8 nm, both P and B impurities can enter into the Si NCs more easily due to the relaxation of stress in the larger-sized Si NCs. Our theoretical results are in good agreement with the experimental observations.
Doping in Si nanocrystals is an interesting topic and to directly study the dopants distribution in phosphorous/boron co-doping circumstance is one of the important issue nowadays. In this study, atom probe tomography is performed to study the structures and impurity distribution in phosphorous/boron co-doped Si nanocrystals/SiO2 multilayers. Comparing with phosphorous singly-doped Si nanocrystals, it is interesting to find the phosphorous concentration in co-doped samples can be significantly improved. Theoretical simulation suggests that phosphorous-boron pairs are formed in co-doped Si nanocrystals with the lowest formation energy, which also reduce the formation energy of phosphorous in Si nanocrystals. The results indicate co-doping can promote more phosphorous impurities enter into the near-surface and inner sites of Si nanocrystals, which provides an interesting way to regulate the electronic and optical properties of Si nanocrystals like the observed enhancement of conductivity and sub-band light emission.
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