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Abstract The strong ligand effect in B‐doped Pd‐based (PdB) catalysts renders them a promising anode for constructing formic acid fuel cells (FAFCs) exhibiting high power density and outstanding stability. However, the enhancement of the oxidation barrier is unavoidable in this alloy system owing to the electron transfer (ET) from B to Pd. In this study, a hydrogen doping strategy is employed to open charge freedom in PdB compounds and boost their formic acid oxidation reaction (FAOR) activity by suppressing the ET process. The resulting hydrogen‐doped PdB (PdBH) exhibits an ultrahigh mass activity of up to 1.2A mg−1Pd, which is 3.23 times that of the PdB catalyst and 9.55 times that of Pd black. Detailed experimental and theoretical studies show that the interstitial hydrogen leads to enhanced orbital hybridization and reduced electron density around Pd. This optimized ligand effect weakens the carbon monoxide adsorption and increases the direct pathway preference of PdBH, resulting in its outstanding catalytic activity for the FAOR. The development of this high‐performance hydrogen‐doped PdB catalyst is an important step toward the construction of advanced light element co‐doped metal catalysts.

Abstract The development of an efficient catalyst for formic acid electrocatalytic oxidation reaction (FAEOR) is of great significance to accelerate the commercial application of direct formic acid fuel cells (DFAFC). Herein, palladium phosphide (PdxPy) porous nanotubes (PNTs) with different phosphide content (i.e., Pd3P and Pd5P2) are prepared by combining the self‐template reduction method of dimethylglyoxime‐Pd(II) complex nanorods and succedent phosphating treatment. During the reduction process, the self‐removal of the template and the continual inside–outside Ostwald ripening phenomenon are responsible for the generation of the one‐dimensional hollow and porous architecture. On the basis of the unique synthetic procedure and structural advantages, Pd3P PNTs with optimized phosphide content show outstanding electroactivity and stability for FAEOR. Importantly, the strong electronic effect between Pd and P promotes the direct pathway of FAEOR and inhibits the occurrence of the formic acid decomposition reaction, which effectively enhances the FAEOR electroactivity of Pd3P PNTs. In view of the facial synthesis, excellent electroactivity, high stability, and unordinary selectivity, Pd3P PNTs have the potential to be an efficient anode electrocatalyst for DFAFC.

Abstract Nearly theoretical 100% atomic utilization (supposing each atom could serve as independent sites to play a role in catalyz) of single‐atom catalysts (SACs) makes it highly promising for various applications. However, for most SACs, single‐atom sites are trapped in a solid carbon matrix, which makes the inner parts hardly available for reaction. Herein, a hollow N‐doped carbon confined single‐atom Rh (Rh‐SACs/HNCR) is developed via a coordination‐template method. Both aberration‐corrected scanning transmission electron microscopy and energy dispersive X‐ray spectroscopy mapping confirm the uniform distribution of Rh single atoms. Owning to the unique hollow structure and effective carbon confinement, excessive conversion from pyridinic/pyrrolic N to graphic N is hindered. As a proof of concept, Rh‐SACs/HNCR exhibits superior activity, stability, selectivity, and anti‐poisoning capability in formic acid oxidation reaction compared with the counterpart Rh/C, Pd/C, and Pt/C catalysts. This work provides a powerful strategy for synthesizing hollow carbon confined single‐atom catalysts apply in various energy‐related systems.

Exploring a new strategy for the removal of adsorbed CO (CO*) on a Pt surface at a low potential is the key to achieving enhanced catalysis for the formic acid oxidation reaction (FAOR); however, the development of such a strategy remains a significant challenge. Herein, we report a class of Au/PtCo heterojunction nanowires (HNWs) as efficient electrocatalysts for accelerating the FAOR. This heterojunction structure and the induced Co alloying effects can facilitate formic acid adsorption/activation on Pt with high CO tolerance, generating the FAOR pathway from dehydration to dehydrogenation. The optimized Au23/Pt63Co14 HNWs showed the highest specific and mass activities of 11.7 mA cm−2Pt and 6.42 A mg−1Pt reported to date, respectively, which are considerably higher than those of commercial Pt/C. DFT calculations confirmed that the electron-rich Au segment enhances the electronic activity of the PtCo NWs, which not only allows the construction of a highly efficient electron transfer channel for the FAOR but also suppresses CO formation.

Electrochemical energy storage and conversion toward sustainable carbon neutrality cycle is of great interest in today's society. In this perspective, we highlight the interconversion between carbon dioxide and formic acid by means of electrocatalytic CO2 reduction reaction (CO2RR) and formic acid oxidation reaction (FAOR) as an effective way to achieve that goal. In line with the distinctive catalytic nature of Pd to reversibly drive both FAOR and CO2RR, we first illustrate the intimate mechanistic relation between these two reversed reactions over Pd surfaces. Next, recent advances in developing Pd-based bifunctional catalysts and relevant optimization strategies are briefly summarized, including geometric structure engineering with preferential facet exposure, construction of crystallographic ordering intermetallic, electronic structure manipulation through metal or metalloid doping to fine tune the binding strength for active and poisoning intermediates. At the end, our viewpoints on the design principles at both microscopic and macroscopic scales are offered toward an efficient CO2 and HCOOH interconversion loop.

Herein, an electrocatalyst with Pd2Ni1 nanoclusters, supporting multiwalled carbon nanotubes (MWCNTs) (referred to Pd2Ni1/CNTs), was fabricated with deep eutectic solvents (DES), which simultaneously served as reducing agent, dispersant, and solvent. The mass activity of the catalyst for formic acid oxidation reaction (FAOR) was increased nearly four times compared to a Pd/C catalyst. The excellent catalytic activity of Pd2Ni1/CNTs was ascribed to the special nanocluster structure and appropriate Ni doping, which changed the electron configuration of Pd to reduce the d-band and to produce a Pd–Ni bond as a new active sites. These newly added Ni sites obtained more OH− to release more effective active sites by interacting with the intermediate produced in the first step of FAOR. Hence, this study provides a new method for preparing a Pd–Ni catalyst with high catalytic performance.

Pt-based catalysts have limited usefulness in direct formic acid fuel cells (DFAFCs) due to their susceptibility to CO poisoning. Combining Pt with Fe atoms is an effective approach for suppressing Pt poisoning by CO. In this work, we fabricate novel carbon-supported FePt alloy nanoparticles (FePt@C) by pyrolyzing Pt nanoparticles encapsulated within mesoporous MIL-101(Fe) (Pt@MIL-101(Fe)). The resulting FePt nanoparticles (Fe3Pt (111)) possess a lower CO adsorption energy (0.64 eV) than the (111) surfaces of Pt, indicating that the FePt nanoparticles are far less susceptible to CO poisoning. The mass activity and current density of a 9.6 wt% FePt@C catalyst are 4.2 and 4.5 times, respectively, higher than those of a commercial Pt/C catalyst. Furthermore, the 9.6 wt% FePt@C catalyst exhibits excellent durability, with only a 0.1% loss of mass activity after 1000 cycles. These results should guide the development of improved anode catalysts for DFAFCs based on MOF precursors.

Energy production and consumption without the use of fossil fuels are amongst the biggest challenges currently facing humankind and the scientific community. Huge efforts have been invested in creating technologies that enable closed carbon or carbon neutral fuel cycles, limiting CO2 emissions into the atmosphere. Formic acid/formate (FA) has attracted intense interest as a liquid fuel over the last half century, giving rise to a plethora of studies on catalysts for its efficient electrocatalytic oxidation for usage in fuel cells. However, new catalysts and catalytic systems are often difficult to compare because of the variability in conditions and catalyst parameters examined. In this review, we discuss the extensive literature on FA electrooxidation using platinum, palladium and non-platinum group metal-based catalysts, the conditions typically employed in formate electrooxidation and the main electrochemical parameters for the comparison of anodic electrocatalysts to be applied in a FA fuel cell. We focused on the electrocatalytic performance in terms of onset potential and peak current density obtained during cyclic voltammetry measurements and on catalyst stability. Moreover, we handpicked a list of the most relevant examples that can be used for benchmarking and referencing future developments in the field.