[ABSTRAK Tujuan dari penelitian ini adalah untuk mengembangkan proses ?green? baruuntuk produksi H2O2 melalui rute sintesis langsung, di mana selama reaksihidrogen dan oksigen saling kontak satu sama lain. Sebuah pendekatanelektrokimia dengan rotating ring disk electrode (RRDE) telah dieksplorasi dandikembangkan secara sistematis yang bertujuan untuk mengukur H2O2 yangdiproduksi. Dua metode yang berbeda - co-reduction and successive reductiondengan menggunakan microwave diadopsi untuk mempersiapkan bimetalnanocatalysts Pd-Au/C. Hubungan antara struktur nanocatalysts dan aktivitaskatalitik dalam proses sintesis langsung diselidiki. Bimetal Pd-Au/C yang telahdisintesa, dikarakterisasi dengan ICP-AES, XRD, SEM, TEM, dan XAS untukpemahaman yang lebih baik dalam aktivitas katalitik sintesis H2O2 secaralangsung.Pendekatan dalam elektrokimia untuk mengukur H2O2 yang dihasilkan darisintesis langsung telah berhasil dilakukan dengan sistem reaksi 2, dimana katalistersebar secara homogen dalam larutan. Kurva kalibrasi variasi konsentrasi H2O2dibuat dalam parameter 0,891 V (vs Ag/AgCl) dan dengan scan rate 50 mV/s. CRPd3%-Au2%/C yang disintesa oleh co-reduction merupakan optimal loadingdengan produktivitas H2O2 65,8 mol.kgcat-1h-1. Produktivitas ini lebih tinggi darisample katalis lainnya, seperti monometallic Pd0%-Au5%/C & Pd5%-Au0%/Cdan bimetal SR Pd-Au/C yang disintesis dengan successive reduction.Produktivitas yang lebih tinggi atau lebih rendah dari satu sampel ke yang laindijelaskan oleh parameter-parameter seperti ukuran partikel, struktur bimetal Pd-Au/C, bidang kristal yang selektif, dan peran paladium dan emas. Ukuran partikelyang lebih kecil cenderung memiliki Pd yang lebih banyak, sedangkan yang lebihbesar cenderung memiliki Au yang lebih banyak. Ukuran partikel yang lebih kecilmemiliki daerah permukaan yang lebih tinggi, sehingga produktivitas meningkat.Namun, jika ukuran partikel terlalu kecil, permukaan yang aktif atau bidangkristal yang selektif mungkin sedikit muncul (seperti dapat dilihat dalam SR Pd-Au/C), sehingga produktivitas menurun.viiDari analisis XAS, CR Pd-Au/C memiliki struktur Au lebih banyak di core dan Pdlebih banyak di shell. Struktur SR Pd-Au/C di beberapa bagian dari katalis adalahAu lebih banyak di core dan Pd lebih banyak di shell, sementara pada bagian lain,Pd lebih banyak di core dan Au lebih banyak di shell. Nilai Q pada SR PdAu(0,638) lebih tinggi daripada CR PdAu (0,605), yang menunjukkan bahwakeberadaan atom Au di shell SR PdAu lebih dari itu CR PdAu. Perbedaan dalamstruktur adalah salah satu alasan mengapa produktivitas H2O2 CR PdAu lebihtinggi dari SR PdAu. Peran Pd adalah untuk memberikan luas permukaan untukoksidasi selektif dari hidrogen dan peran Au adalah untuk menyediakan situs aktifuntuk reaksi dekomposisi dan hidrogenasi H2O2. ABSTRACT The purpose of this study is to develop a new green process for production ofH2O2 through the direct synthesis route, of which the hydrogen and oxygencontacts each other during the reaction. An electrochemical approach with therotating ring disk electrode (RRDE) had been systematically explored anddeveloped accordingly to measure the produced H2O2. Two different methods ?co-reduction and successive reduction prepared in the microwave were adopted toprepare bimetallic Pd-Au/C nanocatalysts. The relationship between the structureof prepared nanocatalysts and their catalytic activity in the direct synthesisprocess were investigated. As synthesized bimetallic Pd-Au/C were characterizedby ICP-AES, XRD, SEM, TEM, and XAS for better understanding in the catalyticactivity of direct synthesis of H2O2.The approach in the electrochemical to measure H2O2 produced from the directsynthesis has been successfully done with the reaction system 2, where thecatalyst is dispersed homogenously in the solution. The calibration curve of thedifferent concentration of H2O2 is made in the parameter of 0.891 V (vs Ag/AgCl)and with the scan rate 50 mV/s. The optimum loading of samples prepared by coreduction was observed in CR Pd3%-Au2%/C with the productivity of H2O2 is65.8 mol.kgcat-1h-1. This productivity is higher than the other prepared catalysts,such as monometallic Pd0%-Au5% & Pd5%-Au0% and bimetallic SR Pd-Au/Cthat is prepared by successive reduction. The higher or the lower productivity ofone sample to another is explained by the parameter of the particle size, thestructure of the bimetallic Pd-Au/C, the selective crystalline plane, and the role ofpalladium and gold. The smaller the particle size tends to Pd rich, while the largerone tends to Au rich. The smaller particle size yielded in the high surface area,thus the productivity increases. However, if the particle size is too small, theactive site or selective crystalline plane may be slightly appeared (as can be seenin SR Pd-Au/C), thus the productivity decreases.From XAS analysis, the structure CR Pd-Au/C is Au rich in core and Pd rich inshell. The structure of SR PdAu at some part of catalyst is Au rich in core and Pdrich in shell, while at the other part, the structure is Pd in core and Au in shell.ixThe Q value of SR PdAu (0.638) is higher than that of CR PdAu (0.605), whichindicates that the existence of Au atoms in the shell of SR PdAu is more than thatof CR PdAu. The difference in their structure is one reason why the H2O2productivity of CR PdAu is higher than SR PdAu. The role of Pd is to provide thesurface area for the selective oxidation of hydrogen and the role of Au is toprovide inactive site for the reaction of decomposition and hydrogenation ofH2O2., The purpose of this study is to develop a new green process for production ofH2O2 through the direct synthesis route, of which the hydrogen and oxygencontacts each other during the reaction. An electrochemical approach with therotating ring disk electrode (RRDE) had been systematically explored anddeveloped accordingly to measure the produced H2O2. Two different methods –co-reduction and successive reduction prepared in the microwave were adopted toprepare bimetallic Pd-Au/C nanocatalysts. The relationship between the structureof prepared nanocatalysts and their catalytic activity in the direct synthesisprocess were investigated. As synthesized bimetallic Pd-Au/C were characterizedby ICP-AES, XRD, SEM, TEM, and XAS for better understanding in the catalyticactivity of direct synthesis of H2O2.The approach in the electrochemical to measure H2O2 produced from the directsynthesis has been successfully done with the reaction system 2, where thecatalyst is dispersed homogenously in the solution. The calibration curve of thedifferent concentration of H2O2 is made in the parameter of 0.891 V (vs Ag/AgCl)and with the scan rate 50 mV/s. The optimum loading of samples prepared by coreduction was observed in CR Pd3%-Au2%/C with the productivity of H2O2 is65.8 mol.kgcat-1h-1. This productivity is higher than the other prepared catalysts,such as monometallic Pd0%-Au5% & Pd5%-Au0% and bimetallic SR Pd-Au/Cthat is prepared by successive reduction. The higher or the lower productivity ofone sample to another is explained by the parameter of the particle size, thestructure of the bimetallic Pd-Au/C, the selective crystalline plane, and the role ofpalladium and gold. The smaller the particle size tends to Pd rich, while the largerone tends to Au rich. The smaller particle size yielded in the high surface area,thus the productivity increases. However, if the particle size is too small, theactive site or selective crystalline plane may be slightly appeared (as can be seenin SR Pd-Au/C), thus the productivity decreases.From XAS analysis, the structure CR Pd-Au/C is Au rich in core and Pd rich inshell. The structure of SR PdAu at some part of catalyst is Au rich in core and Pdrich in shell, while at the other part, the structure is Pd in core and Au in shell.ixThe Q value of SR PdAu (0.638) is higher than that of CR PdAu (0.605), whichindicates that the existence of Au atoms in the shell of SR PdAu is more than thatof CR PdAu. The difference in their structure is one reason why the H2O2productivity of CR PdAu is higher than SR PdAu. The role of Pd is to provide thesurface area for the selective oxidation of hydrogen and the role of Au is toprovide inactive site for the reaction of decomposition and hydrogenation ofH2O2.] |