No abstract

Due to the low cost, good chemical stability and structural diversity, hard carbon has been considered as an important anode material for potassium-ion batteries (PIBs). However, due to the large diameter of K+, PIBs with both excellent rate performance and long-life is still challenging. Herein, sulfur (S), phosphorus (P) co-doped hard carbon anode are synthesized via polymerization of thiophene and phytic acid and the following concise pyrolysis strategy. S in hard carbon can used as reactive sites for K+ storage and P doping will effectively improve wettability of electrolyte. After temperature regulation, the fabricated SP-700 with dual and abundant heteroatom doping exhibits high initial reversible capacity (412 mAh g−1 at 0.05 A g−1), excellent rate performance (130 mAh g−1 at 5 A g−1) and stable cyclic performance (94 mAh g−1 after 1500 cycles at 2 A g−1).

Developing highly efficient photocatalysts for converting CO2 into solar fuels is of great importance for energy sustainability. However, efficient photoreduction of CO2 over the heterogeneous catalyst is hindered by lack of precisely controlled active sites and poor contact between active sites and the semiconductor, which leads to low selectivity and poor photochemical stability of the catalyst. Herein, utilizing highly stable and readily tunable photoresponsive covalent triazine frameworks (CTFs) as intriguing platforms, the well-defined molecular catalysts are directly knitting into CTFs by an in-situ covalent-bonding strategy for the first time to afford photo-responsive single-site Ru CTFs. The robust chemical knitting of molecular catalyst with porous CTFs provides the atomically dispersed catalytic sites, providing enhanced light absorption and CO2 diffusion. Significantly, the resulting Ru-CTF can reduce CO2 to formic acid under visible light with excellent selectivity (98.5%) and activity (6270 μmol·gcat-1), which greatly outperforms most other polymer semiconductors reported so far. However, the homogeneous Ru counterpart (Ru(dcbpy)(CO)2Cl2, dcbpy=2,2'-bipyridine-5,5'-dicarbonitrile) exhibits a low activity and deactivates within 1 h. Systematic investigations reveal that the introduction of single sites (Ru-N2) can promote photoinduced charge separation and CO2 activation, thus significantly enhancing the photocatalytic performance. The combination of in-situ fourier transform infrared spectrometer (in-situ FTIR), density functional theory (DFT) calculations and luminescence quench experiments were particularly investigated to confirm the possible photocatalytic CO2 reduction mechanism over Ru-CTF. This work provides a new pathway and significant insights into the design of CTF-based single-site photocatalysts for highly selective CO2 photoreduction.

Photocatalytic dehydrogenation of formic acid (FA) at room temperature is a promising way to meet the increasing demand for hydrogen energy. In this work, we loaded nanoparticles of plasmonic AuPd alloys on the acetylene functionalized covalent triazine frameworks (CTFs) for the design of Mott-Schottky catalysts (AuPd/CTFs) with further application to photocatalytic hydrogen production from FA. Experimental data showed that the introduction of acetylene (-C≡C-) unit and AuPd alloy into the CTF could significantly enhance the performance of hydrogen evolution. The results of photoelectrochemical tests showed that the introduction of carbon-carbon triple bonds and AuPd alloy could adjust the electronic structure of CTF and inhibit charge recombination. Thus, benefiting from these positive effects, the FA photocatalytic decomposition by the obtained AuPd-CTF-EDDBN photocatalyst yielded H2 at a good rate of 10600 μmol·gcat −1·h−1.