Methane is one of the major greenhouse gases that affect climate change. To mitigate anthropogenic CH4 emissions effectively, it is necessary to measure and monitor CH4 emissions from the production and transport of fossil fuels. Therefore, it is important for NMIs to demonstrate measurement equivalence for the standard gases of CH4. This is the third comparison on methane in nitrogen or air. The first comparison is the key comparison of CCQM-K82 (ambient level methane in air) and the second comparison is the supplementary comparison of APMP.QM-S7 (2000 μmol/mol methane in nitrogen). As a supplementary comparison, the purpose of this comparison is to study the comparability of CH4 standard gas mixtures at emission level (0.05 cmol/mol - 0.5 mol/mol in nitrogen or air). Furthermore, this comparison can provide a link to APMP.QM-S7 through KRISS who participated in both previous comparisons. In this comparison, KRISS prepared gas standards and sent to participants. Each participant measured the standard on their laboratory and reported their measurement results to KRISS according to the measurement protocol. This report describes the results of a supplementary comparison for methane in nitrogen at 2000 μmol/mol. Main text To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

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The tungsten trioxide (WO3) and copper(II) oxide (CuO) photoelectrodes have been fabricated from acidic aqueous solution of peroxy-tungstate and basic aqueous solution of copper sulphate-lactic acid respectively, by electrodeposition method. The samples produced were calcined at 450 °C for 30 minutes before the deposition of second layer. The CuO was layered on WO3 sample by electrodeposition of basic aqueous solution of copper sulphate-lactic acid, followed by annealing process at 450 °C for 30 minutes. On the other hand, the WO3 layer was casted onto CuO sample by sol-gel method and it was annealed at 450 °C for 30 minutes. The resulting samples were then characterized by XRD to confirm their structures. Photoelectrochemical characterization of the WO3, CuO and WO3-CuO bilayer photoelectrodes were carried out under 100 W xenon light illumination, in 0.5 M sodium sulphate solution with saturated calomel electrode (SCE) reference electrode and platinum counter electrode. The PEC stability of the electrodes was evaluated at -0.7 V vs SCE under irradiated condition.

Various modifications of the titanium dioxide thin films have been done in fulfilling the photoelectrode requirements for photoelectrochemical water splitting reaction. In this study, surface passivation of TiO 2 by hematite-Fe 2 O 3 was reported. Electrodeposition technique was used to deposit the Fe 2 O 3 onto the TiO 2 /FTO film with variation of time. X-ray diffraction (XRD), Scanning Electron Microscope (SEM) and UV-Vis spectroscopic analyses were used to characterize the electrode. Plane-wave-based pseudopotential density functional theory (DFT) calculations were used to analyze the electronic structure and charge potential at the surface of the electrode. The photocurrent measurement showed that current density of TiO 2 /Fe 2 O 3 electrode was higher than the TiO 2 /FTO under the same illumination intensity of 100 mWcm -2 . The highest current density was produced by 5 minutes electrodeposition of Fe 2 O 3 , which also shifted the absorption to visible region at the threshold wavelength of 518 nm.Keywords : titanium dioxide, iron(III) oxide, passivation layer, band gap Abstrak Pelbagai pengubahsuaian titanium dioksida filem nipis telah dilakukan untuk memenuhi keperluan fotoelektrod bagi tindak balas fotoelektrokimia pembelahan molekul air. Dalam kajian ini, dilaporkan pempasifan permukaan TiO 2 dengan bijih besi-Fe 2 O 3 . Teknik pengelektroenapan digunakan untuk mendepositkan Fe 2 O 3 ke TiO 2 /FTO filem dengan pelbagai masa pengelektroenapan. Analisis XRD, SEM dan UV-Vis spektroskopi telah digunakan untuk mencirikan elektrod. pengiraan teori fungsi ketumpatan (DFT) berasaskan planar gelombang pseudopotential telah digunakan untuk menganalisis struktur elektronik dan potensi caj di permukaan elektrod. Pengukuran arusfoto menunjukkan bahawa ketumpatan arus TiO 2 /Fe 2 O 3 elektrod adalah lebih tinggi daripada TiO 2 /FTO bawah keamatan pencahayaan yang sama, 100 mWcm -2 . Ketumpatan semasa tertinggi dihasilkan oleh 5 minit pengelektroenapan Fe 2 O 3 , yang mana penyerapan beralih ke kawasan yang boleh dilihat pada panjang gelombang ambang 518 nm.Kata kunci: titanium dioksida, ferum (III) oksida, lapisan pasif, sela jalur