Ce Yang

Abstract The great interest in fuel cells inspires a substantial amount of research on nonprecious metal catalysts as alternatives to Pt‐based oxygen reduction reaction (ORR) electrocatalysts. In this work, bimodal template‐based synthesis strategies are proposed for the scalable preparation of hierarchically porous M–N–C (M = Fe or Co) single‐atom electrocatalysts featured with active and robust MN 2 active moieties. Multiscale tuning of M–N–C catalysts regarding increasing the number of active sites and boosting the intrinsic activity of each active site is realized simultaneously at a single‐atom scale. In addition to the antipoisoning power and high affinity for O 2 , the optimized Fe–N–C catalysts with FeN 2 active site presents a superior electrocatalytic activity for ORR with a half‐wave potential of 0.927 V (vs reversible hydrogen electrode (RHE)) in an alkaline medium, which is 49 and 55 mV higher than those of the Co–N–C counterpart and commercial Pt/C, respectively. Density functional theory calculations reveal that the FeN 2 site is more active than the CoN 2 site for ORR due to the lower energy barriers of the intermediates and products involved. The present work may help rational design of more robust ORR electrocatalysts at the atomic level, realizing the significant advances in electrochemical conversion and storage devices.

Iron carbide nanoparticles have long been considered to have great potential in new energy conversion, nanomagnets, and nanomedicines. However, the conventional relatively harsh synthetic conditions of iron carbide hindered its wide applications. In this article, we present a facile wet-chemical route for the synthesis of Hägg iron carbide (Fe(5)C(2)) nanoparticles, in which bromide was found to be the key inducing agent for the conversion of Fe(CO)(5) to Fe(5)C(2) in the synthetic process. Furthermore, the as-synthesized Fe(5)C(2) nanoparticles were applied in the Fischer-Tropsch synthesis (FTS) and exhibited intrinsic catalytic activity in FTS, demonstrating that Fe(5)C(2) is an active phase for FTS. Compared with a conventional reduced-hematite catalyst, the Fe(5)C(2) nanoparticles showed enhanced catalytic performance in terms of CO conversion and product selectivity.

Abstract A one‐step ligand‐free method based on an adsorption–precipitation process was developed to fabricate iridium/cerium oxide (Ir/CeO 2 ) nanocatalysts. Ir species demonstrated a strong metal–support interaction (SMSI) with the CeO 2 substrate. The chemical state of Ir could be finely tuned by altering the loading of the metal. In the carbon dioxide (CO 2 ) hydrogenation reaction it was shown that the chemical state of Ir species—induced by a SMSI—has a major impact on the reaction selectivity. Direct evidence is provided indicating that a single‐site catalyst is not a prerequisite for inhibition of methanation and sole production of carbon monoxide (CO) in CO 2 hydrogenation. Instead, modulation of the chemical state of metal species by a strong metal–support interaction is more important for regulation of the observed selectivity (metallic Ir particles select for methane while partially oxidized Ir species select for CO production). The study provides insight into heterogeneous catalysts at nano, sub‐nano, and atomic scales.

Large carbon networks featuring hierarchical pores and atomically dispersed metal sites (ADMSs) are ideal materials for energy storage and conversion due to the spatially continuous conductive networks and highly active ADMSs. However, it is a challenge to synthesize such ADMS-decorated carbon networks. Here, an innovative fusion-foaming methodology is presented in which energetic metal-organic framework (EMOF) nanoparticles are puffed up to submillimeter-scaled ADMS-decorated carbon networks via a one-step pyrolysis. Their extraordinary catalytic performance towards oxygen reduction reaction verifies the practicability of this synthetic approach. Moreover, this approach can be readily applicable to a wide range of unexplored EMOFs, expanding scopes for future materials design.