# Noble Metal-Based Heterogeneous Catalysts for Electrochemical Hydrogen Evolution Reaction
## 4 Noble Metal-Based Heterogeneous Catalysts
### Interface Engineering
#### 4.2.1 Metal/Metal Core-Shell Nanostructures
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Catalyst** & **Electrolyte** & \
\begin{tabular}{c} **Overpotential** \\ **(\(\eta_{10}\)/mV)** \\ \end{tabular} &
\begin{tabular}{c} **Tafel Slope** \\ **(mV-dec\({}^{-1}\))** \\ \end{tabular} & **Ref.** \\ \hline
4H/_fc_ Au@PdAg NRBs a & 0.5 M H\({}_{2}\)SO\({}_{4}\) & 26.2 & 30 & [83] \\ Pd@Ru NRs a & 0.5 M H\({}_{2}\)SO\({}_{4}\) & 37 & 33 & [84] \\ Pt-MoS\({}_{2}\) & 0.5 M H\({}_{2}\)SO\({}_{4}\) & - & 40 & [85] \\ Pt-MXene-CNTs a & 0.5 M H\({}_{2}\)SO\({}_{4}\) & 62 & 66.6 & [86] \\ Ru@C\({}_{2}\)N & 0.5 M H\({}_{2}\)SO\({}_{4}\) & 22 & 30 & [87] \\ C\({}_{3}\)N\({}_{4}\)/Pd & 0.5 M H\({}_{2}\)SO\({}_{4}\) & - & 116 & [88] \\ C\({}_{3}\)N\({}_{4}\)/Pt & 0.5 M H\({}_{2}\)SO\({}_{4}\) & - & 71 & [88] \\ Ru@MWCNT a & 0.5 M H\({}_{2}\)SO\({}_{4}\) & 13 & 27 & [89] \\ Pt@2D MXene & 0.5 M H\({}_{2}\)SO\({}_{4}\) & 80 & 66.6 & [90] \\ Pt@3D MXene & 0.5 M H\({}_{2}\)SO\({}_{4}\) & 13 & 24.2 & [90] \\ Ru SAs@PN a & 0.5 M H\({}_{2}\)SO\({}_{4}\) & 24 & 38 & [91] \\ Pt@MoS\({}_{2}\)/NiS\({}_{2}\) & 0.5 M H\({}_{2}\)SO\({}_{4}\) & 34 & 40 & [92] \\ Pt/Ni@Al\({}_{2}\)O\({}_{3}\) & 0.5 M H\({}_{2}\)SO\({}_{4}\) & 34 & 35 & [14] \\ Pd@Ru NRs a & 0.1 M KOH & 41 & 36 & [93] \\ Pd@Ru NRs a & 1 M KOH & 30 & 30 & [84] \\ Pt@NCs/BP a & 1 M KOH & 22 & 19 & [94] \\ Pt-NiFe LDH/CC a & 1 M KOH & 28 & 39 & [95] \\ Pt/Ni-MOF & 1 M KOH & 25 & 42.1 & [96] \\ Ru@C\({}_{2}\)N & 1 M KOH & 17 & 38 & [87] \\ Ru@MWCNT a & 1 M KOH & 17 & 27 & [89] \\ \hline \hline \end{tabular}  
* NRBs: nanoribbons, NRs: nanorods, CNTs: carbon nanotubes, MWCNT: multiwalled carbon nanotube, PN: phosphorus nitride imide nanotubes, NPs: nanoplates, NCs: nanoclusters, BP: black phosphorus, CC: carbon fiber cloth.  
\end{table} 
Table 2: The HER Performance of Various Interfacial Electrocatalysts under Different Reaction Conditions. excellent catalytic activity is due to its abundant atomic steps, nanodendritic surface, multi-component synergistic effect of the shell and distinct crystal structure. This classic work provides a current strategy for the controlled synthesis of the crystal structure of noble metal nanomaterials. In addition, [PERSON] et al. [84] synthesized mesoporous Pd@Ru core-shell bimetallic nanorods composed of _fcc_ Pd and _hcp_ Ru. The DFT calculation shows that Ru/Pd (111) interface structure enhanced the alkaline HER activity (\(\eta_{10}\) = 30 mV in 1.0 M KOH). The 2D core-shell nanostructure is mainly covered with nanoplates and nanosheets. Ru-based nanoplates have attracted extensive attention in recent years due to their distinct 2D structure and excellent catalytic performance. However, the synthesis of Ru-based nanoplates remains a challenge, especially the controlled synthesis of 2D structures with atomic thickness. [PERSON] et al. [93] successfully synthesized core-shell Pd@Ru nanoplates with _fcc_ structure with a simple solvothermal method using Pd nanoplates as the substrate. The thickness and crystal structure of the Ru shell can be adjusted by merely changing the amount of Ru precursor. With the increase in the Ru shell thickness, the HER activity of Pd@Ru firstly increased and then decreased. This is because, with the increase in the Ru shell thickness, its crystal structure changed from the _fcc_ to the _hcp_ phase. In fact, shell thickness is critical to catalytic activity. The electron coupling and strain effects are different between the shell and core with different thicknesses. A shell with the thickness of a single atomic layer has the highest utilization rate. However, it is not a balanced and stable configuration, and adverse diffusion will occur on the surface atom after long-term operation or at high temperatures. Therefore, adjusting the thickness of the shell accurately requires higher requirements for the structure synthesis and interface structure.