Optimization of Pt atom utilization efficiency is critical for the development of proton-exchange-membrane fuel cells. Here we aim to develop an efficient oxygen reduction reaction (ORR) catalyst with a low Pt content through the concurrent modification of Pt-Co alloy catalysts and carbon substrate. In the present study, ultrafine Pt-Co alloy nanoparticles are successfully synthesized and stabilized by topological carbon defects via adopting the ammonia thermal treatment. Despite the low Pt loading, the obtained catalyst exhibits an impressive half-wave potential of 0.926 V versus the reversible hydrogen electrode in 0.1 M HClO₄ electrolyte. Furthermore, the durability testing using the timed-current method demonstrates a tiny loss of only 3.6% after 12 h. Both experimental results and theoretical calculations demonstrate that topological carbon defects significantly enhance the charge transfer processes at the alloy/carbon interface, contributing to the strong electronic metal-support interactions between the Pt-Co alloy nanoparticles and topological carbon defects. These interactions, along with the alloy effect, play a crucial role in promoting the ORR performance in acidic media.

The urea oxidation reaction has attracted increasing attention. Here, porous rod-like Ni₂P/Ni assemblies, which consist of numerous nanoparticle subunits with matching interfaces at the nanoscale have been synthesized via a simple phosphating approach. Density functional theory calculations and density of states indicate that porous rod-like Ni₂P/Ni assemblies can significantly enhance the activity of chemical bonds and the conductivity compared with NiO/Ni toward the urea oxidation reaction. The optimal catalyst of Ni₂P/Ni can deliver a low overpotential of 50 mV at 10 mA·cm^-2 and Tafel slope of 87.6 mV·dec^-1 in urea oxidation reaction. Moreover, the constructed electrolytic cell exhibits a current density of 10 mA·cm^-2 at a cell voltage of 1.47 V and an outstanding durability in the two-electrode system. This work has provided a new possibility to fabricate metal phosphides-metal assemblies with advanced performance.

Developing efficient carbon-based metal-free electrocatalysts can bridge the gap between laboratory studies and practical applications of CO₂ reduction. However, along with the ambiguous understanding of the active sites in carbon-based electrocatalysts, carbon-based electrocatalysts with high selectivity and satisfactory stability for electroreduction of CO₂ remain rare. Here, using the nitrogen rich silk cocoon as a precursor, carbon-based electrocatalysts with intrinsic defects can be prepared for efficient and long-term electroreduction of CO₂ by a simple two-step carbonization. The obtained electrocatalyst can catalyze CO₂ reduction to CO with a Faradaic efficiency of ~ 89% and maintain good selectivity for about 10 days. Particularly, our experimental studies suggest that in-plane defects are the main active sites on which the rate-determining step for CO₂ reduction should be the direct electron transfer to CO₂ but not the proton-coupled electron transfer. Further theoretical calculations consistently demonstrate that the intrinsic defects in carbon matrix, particularly the pentagon-containing defects, act as main active sites to accelerate the direct electron transfer for CO₂ reduction. In addition, our synthetic approach can convert egg white into efficient catalysts for CO₂ electroreduction. These findings, providing new insights into the biomass-derived catalysts, should pave the way for fabricating efficient and stable carbon-based electrocatalysts with catalytically active defects by using naturally abundant precursors.