TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Composition: The gold-silver alloy article comprises (in weight%) gold (37.5) and silver (62.5). The concentration of ion solution is 100 mu mol/dm3-100 mmol/dm3 of copper, silver, or lead ion. The concentration of platinum ion solution is 10 mmol/dm3. The concentration of gold ion solution is 1 mmol/dm3. Preferred Process: The gold-silver alloy article is immersed in de-alloying solution comprising nitric acid (65-85 weight%) at 20-30 degrees C for 120 minutes. The deposition of monoatomic layer or lower layer of copper is completed by immersing the nanoporous gold article/electrode in copper ion solution under constant voltage of 0.25-0.45V (vs. reversible hydrogen electrode (RHE) potential) for 5 minutes. The deposition of monoatomic layer or lower layer of copper is completed by immersing the nanoporous gold article/electrode in silver ion solution under constant voltage of 0.65-0.85V (vs. RHE) for 5 minutes. The deposition of monoatomic layer or lower layer of copper is completed by immersing the nanoporous gold article/electrode in lead ion solution under constant voltage of -0.1 to 0.1V (vs. RHE) for 5 minutes. The copper, silver or lead-nanoporous gold article is immersed in the platinum ion solution for 10 minutes. The deposition of monoatomic layer or lower layer of copper is completed by immersing the nanoporous gold-platinum article/electrode in copper ion solution under constant voltage of 0.25-0.45V (vs.RHE) for 5 minutes. The deposition of monoatomic layer or lower layer of copper is completed by immersing the nanoporous gold-platinum article/electrode in silver ion solution under constant voltage of 0.65-0.85V (vs. RHE) for 5 minutes. The deposition of monoatomic layer or lower layer of lead is completed by immersing the nanoporous gold-platinum article/electrode in lead ion solution under constant voltage of -0.1-0.1V (vs. RHE) for 5 minutes. The copper, silver or lead-nanoporous gold-platinum article is immersed in the gold ion solution for 10 minutes. Preferred Properties: The gold-silver alloy has length of 6-20 cm, width of 1-5 cm and thickness of 0.1-10 mu m. The number of repeats of process such as attaching, depositing, removing, replacing and cleaning involved in forming nanoporous gold-platinum article is 0-1. The number of repeats of process such as depositing, removing, replacing and cleaning involved in forming nanoporous gold-platinum-gold article is 0-1. 16. The catalyst has thickness of 0.1-10 mu m, width of 1-5 cm and length of 6-20 cm. The catalyst is metal alloy having three-dimensional nanoporous structure, and nanopore size of 2-100 nm. Preferred Layer: The metal alloy has atomic or subatomic layers of platinum and/or gold on the surface. The gold layer is provided on the platinum layer.