Low-Temperature Acetylene Semi-Hydrogenation over the Pd₁–Cu₁ Dual-Atom Catalyst

Abstract

The atomically dispersed metal catalyst or single-atom catalyst (SAC) with the utmost metal utilization efficiency shows excellent selectivity toward ethylene compared to the metal nanoparticles catalyst in the acetylene semi-hydrogenation reaction. However, these catalysts normally work at relatively high temperatures. Achieving low-temperature reactivity while preserving high selectivity remains a challenge. To improve the intrinsic reactivity of SACs, rationally tailoring the coordination environments of the first metal atom by coordinating it with a second neighboring metal atom affords an opportunity. Here, we report the fabrication of a dual-atom catalyst (DAC) that features a bonded Pd1–Cu1 atomic pair anchoring on nanodiamond graphene (ND@G). Compared to the single-atom Pd or Cu catalyst, it exhibits increased reactivity at a lower temperature, with 100% acetylene conversion and 92% ethylene selectivity at 110 °C. This work provides a strategy for designing DACs for low-temperature hydrogenation by manipulating the coordination environment of catalytic sites at the atomic level.

Synthetic Strategies of Supported Pd-Based Bimetallic Catalysts for Selective Semi-Hydrogenation of Acetylene: A Review and Perspectives

“…Just as the name implies, bimetallic DACs are a kind of catalyst that requires the introduction of another atom to combine the parent active metal, forming dual active sites in isolation; it can be viewed as SAAs catalysts for particle size reduction to the limit case. By reason of unique electronic, adsorption and synergistic effects, bimetallic DACs are also a very suitable catalyst system for the selective hydrogenation of acetylene [ 41 , 163 , 164 , 165 , 166 ].…”

“…In the case of supported Pd 1 SAAs catalysts, the preparation methods vary, and the technical process has been relatively mature, although most of the methods for the preparation of bimetallic nano catalysts are still suitable and have been optimized and employed for their synthesis, such as incipient wetness impregnation (IWI) [ 18 , 167 , 168 ], deposition-precipitation (DP) [ 169 ], galvanic replacement (GR) [ 170 , 171 ], controlled surface reaction (CSR) [ 97 ], colloidal electroless reduction deposition (colloidal eless-RD) [ 172 , 173 ], the sol-gel method [ 174 ], physical vapor deposition (PVD) [ 146 , 147 , 175 ], electrochemical deposition (ECD) [ 176 ], photochemical reduction (PR) [ 177 ], and atomic layer deposition (ALD) [ 178 ]. For supported bimetallic DACs, the currently reported synthesis methods include photochemical reduction (PR) [ 164 ], deposition-precipitation (DP) [ 41 ], as well as thermal pyrolysis and even subsequent acid leading [ 179 , 180 ]. The illustrations for the specific synthetic methods, as well as characterization results of SAAs and DACs are shown in Figure 18 .…”

“…At present, indeed, there are several non-precious metal catalysts emerging and showing potential for the selective semi-hydrogenation of acetylene, such as Ni-based [ 30 , 31 , 32 ] and Cu-based [ 8 , 33 , 34 , 35 , 36 , 37 ] catalysts. Even so, supported forms of Pd-based catalysts remain the industrial catalyst of choice to date [ 38 , 39 , 40 , 41 , 42 , 43 , 44 ]. Because Pd is the most efficient metal for this reaction due to its unique electronic structures as well as its superior ability to dissociate dihydrogen and activate acetylene, e.g., supported Pd nanoparticles can easily catalyze the reaction to achieve complete conversion of acetylene even at room temperature and normal pressure [ 40 , 41 , 42 ].…”

“…Even so, supported forms of Pd-based catalysts remain the industrial catalyst of choice to date [ 38 , 39 , 40 , 41 , 42 , 43 , 44 ]. Because Pd is the most efficient metal for this reaction due to its unique electronic structures as well as its superior ability to dissociate dihydrogen and activate acetylene, e.g., supported Pd nanoparticles can easily catalyze the reaction to achieve complete conversion of acetylene even at room temperature and normal pressure [ 40 , 41 , 42 ]. However, for supported Pd nanoparticles, over which the undesired over-hydrogenation of acetylene to ethane and the dimerization of acetylene further polymerization into green oil also easily occur, this results in lower ethylene selectivity and the catalytic activity [ 38 , 43 , 44 ].…”

“…In view of the above, adequately weakening the adsorption of ethylene, and/or raising the kinetic barrier in the hydrogenation of ethylene, as well as suppressing the coupling-hydrogenation and hydrogenation-coupling to achieve high ethylene selectivity and low production of green oil, should always be the first and foremost challenge for Pd-based catalysts, both in the industry and academia [ 41 ]. To that end, considerable efforts have already been invested to improve selectivity toward ethylene over Pd-based catalysts by different methods [ 2 , 4 , 15 ].…”