Synthesis of Pure Thiophene-Sulfur-Doped Graphene for an Oxygen Reduction Reaction with High Performance.

Various S-bonding configurations existing in sulfur-doped reduced graphene oxide (S-rGO) show different electronic structures and physiochemical properties. Thus, understanding the properties of unique S-bonding configurations requires the construction of S-rGO with only single configuration. Here, we synthesized S-rGO with a pure thiophene-sulfur configuration through a simple and low-cost hydrothermal method by simply controlling the oxidation degree of the graphene oxide (GO) precursor. Through the use of a GO precursor with a high content of C-O groups, pure doping of the thiophene-sulfur configuration in the rGO can be achieved. Further electrochemical characterization reveals an increased electrocatalytic activity of the pure thiophene-sulfur-doped S-rGO in the oxygen reduction reaction, indicating the important role of thiophene-sulfur. The present work deepens the understanding of the functions of doped nonmetal elements in carbon materials in electrocatalysis and helps in the design of high performance electrocatalysts.

Electronic metal-support interaction modulates single-atom platinum catalysis for hydrogen evolution reaction.

Tuning metal-support interaction has been considered as an effective approach to modulate the electronic structure and catalytic activity of supported metal catalysts. At the atomic level, the understanding of the structure-activity relationship still remains obscure in heterogeneous catalysis, such as the conversion of water (alkaline) or hydronium ions (acid) to hydrogen (hydrogen evolution reaction, HER). Here, we reveal that the fine control over the oxidation states of single-atom Pt catalysts through electronic metal-support interaction significantly modulates the catalytic activities in either acidic or alkaline HER. Combined with detailed spectroscopic and electrochemical characterizations, the structure-activity relationship is established by correlating the acidic/alkaline HER activity with the average oxidation state of single-atom Pt and the Pt-H/Pt-OH interaction. This study sheds light on the atomic-level mechanistic understanding of acidic and alkaline HER, and further provides guidelines for the rational design of high-performance single-atom catalysts.

Site-specific electrodeposition enables self-terminating growth of atomically dispersed metal catalysts.

The growth of atomically dispersed metal catalysts (ADMCs) remains a great challenge owing to the thermodynamically driven atom aggregation. Here we report a surface-limited electrodeposition technique that uses site-specific substrates for the rapid and room-temperature synthesis of ADMCs. We obtained ADMCs by the underpotential deposition of a non-noble single-atom metal onto the chalcogen atoms of transition metal dichalcogenides and subsequent galvanic displacement with a more-noble single-atom metal. The site-specific electrodeposition enables the formation of energetically favorable metal-support bonds, and then automatically terminates the sequential formation of metallic bonding. The self-terminating effect restricts the metal deposition to the atomic scale. The modulated ADMCs exhibit remarkable activity and stability in the hydrogen evolution reaction compared to state-of-the-art single-atom electrocatalysts. We demonstrate that this methodology could be extended to the synthesis of a variety of ADMCs (Pt, Pd, Rh, Cu, Pb, Bi, and Sn), showing its general scope for functional ADMCs manufacturing in heterogeneous catalysis.

Plasmonic Nanohybrid with High Photothermal Conversion Efficiency for Simultaneously Effective Antibacterial/Anticancer Photothermal Therapy.

Plasmonic metal/semiconductor nanohybrids hold great promise in photocatalysis and biosensor development; however, their potential phototherapeutic applications are yet fully unexplored. On the other hand, the demand of high laser power density to induce antibacterial photothermal therapeutic effects greatly restricts the practical applicability of the previously developed photothermal nanoagents (PTAs) for anticancer photothermal therapy (PTT). Here, we develop a plasmonic nanohybrid by integrating plasmonic noble metal gold nanorods (AuNRs) with a two-dimensional graphene oxide (2-D GO), capable to perform photothermal ablation of both bacterial pathogens as well as tumor cells, respectively, under low power single near-infrared (NIR) laser activation. Owing to the synergistic plasmonic photothermal effect (PPTT) of dual plasmonic PTAs, the plasmonic AuNR/GO nanohybrid exhibits remarkably higher photothermal conversion efficiency (PCE, 72.59%) than either individual AuNRs or GO under low laser power density (300 mW), leading to enhanced antibacterial/anticancer PTT. In addition, the synergistic plasmonic antibacterial/anticancer PTT induced by the plasmonic nanohybrid is also far superior to individual PTAs (AuNRs or GO), whereas the flow cytometric analysis of heat shock proteins (HSP 70) clearly dictates that the substantial killing of bacterial pathogens/tumor cells is solely due to the synergistic PPTT. Thus, the plasmonic AuNR/GO nanohybrid is a standalone PTA to perform simultaneous antibacterial/anticancer PTT under low power NIR laser activation for only 5 min, without any systemic side effects. The present study provides a clear demonstration about the potential therapeutic impact of plasmonic nanohybrids and thus will surely pave the way to design other hybrid nanoagents with enhanced PCE and integrate them with chemotherapeutic agents, leading to dual-modal chemo-/photothermal antibacterial/anticancer therapy under low power single laser excitation for a short duration.